ReleaseNotes

        and '}'.
      - libc/unisted:  Change brings strtol() and related functions more
        conformant with POSIX.  Corner cases like strtol(-2147483648, NULL,
        10) now pass clang -fsanitize=integer without warnings.  From Juha
        Niskanen.
      - libc/unistd: sleep() was returning remaining nanoseconds (kind of),
        instead the remaining seconds.  From Eunbong Song.
      - termios.h:  Fix CRTSCTS define to include input and output flow. From
        Lorenz Meier.

    * Build/Configuration System:

      - configs/*/defconfig: The buttons example was changed to archbuttons.
        As a result all of the button configurations are broken and need some
        renaming in the defconfig files.  Noted by Frank Berkert.
      - config/*/defconfgs: More fallout from name change of
        apps/examples/buttons to archbuttons.
      - configs:  All QE encoder files.  Last change made timer hard-coded to
        3. Make configurable.
      - configs: Remove all traces of the no-longer existent ARCHBUTTONS
        example.  Remove all button configurations that depended on the
        obsoleted ARCHBUTTON example.
      - minnsh Configurations:  Remove minnsh configurations and support
        logic:  up_getc() and lowinstream.  This was an interesting exercise
        to see just how small you could get NuttX, but otherwise it was not
        useful:  (1) the NSH code violated the OS interface layer by callup
        up_getc() and up_putc() directly, and (2) while waiting for character
        input, NSH would call up_getc() which would hog all of the CPU.  Not a
        reasonable solution other than as a proof of concept.

    * Application Build/Configuration System:

      - Make.defs:  Using wrong link script if native window tool used with
        Cygwin.

    * apps/platform:

      - ESP32 Core v2 Platform: Fix some naming that prevented building the
        C++ support.

    * apps/nshlib:

      - NSH Library:  nsh_getdirpath(), use snprint instead of sprintf to
        avoid possibility of buffer overrun.  Noted by Chung Hwan Kim.

    * apps/system:

      - Remove std_readline().  This called up_getc() and up_putc() directly,
        violating the POSIX OS interface.

    * apps/netutils:

      - FTPD: Fixed bug that didn't free ftpd ressources on exit.  From Pascal
        Speck.
      - NTP client: Fix missing left parenthesis.  From Pierre-Noel Bouteville.
      - cJSON: Import patch to fix:cJSON_PrintUnformatted() behaves unexpected
        if an empty array shall be printed to text. from Jerome Lang
        2012-04-19. From Pierre-Noel Bouteville.
      - esp8266 update cosmetic and many bug fix.  From Pierre-Noel Bouteville.
      - FTPD:  Fix bug un ftpd file or socket may be not closed.  From
        Pierre-Noel Bouteville.

    * apps/modbus:

      - Modbus Master is missing many files and doesn't compile at all. More
        details in
        https://groups.yahoo.com/neo/groups/nuttx/conversations/topics/13734.
        From Vytautas Lukenskas.

    * apps/examples:

      - The examples/qencoder app was trying to init the encoder by a direct
        call into the board, cheating in a local header to declare the
        normally unavailable function prototype.  From Sebastien Lorquet.
      - apps/examples/timer: Should detach signal handler before exiting.
      - examples/qencode: The examples/qencoder app was trying to init the
        encoder by a direct call into the board, cheating in a local header to
        declare the normally unavailable function prototype.  From Sebastien
        Lorquet.
      - apps/examples/archbuttons:  Removed becaue it violates OS interface
        principles.
      - examples/adc, pwm, can: Remove all usage of BOARDIOC_ADCTEST_SETUP,
        BIOARDIOC_PWMSETUP.  Remove BOARDIOC_CAN_INITIALIZE.  CAN
        initialization is now done in the board initialization logic just like
        every other device driver.
      - examples/ostest: Add some delays to the pthread cancellation test.
        With deferred cancellation enabled, things happen more asynchronously.

NuttX-7.20 Release Notes
------------------------

The 120th release of NuttX, Version 7.20, was made on March 8, 2017,
and is available for download from the Bitbucket.org website.  Note
that release consists of two tarballs:  nuttx-7.20.tar.gz and
apps-7.20.tar.gz.  These are available from:

    https://bitbucket.org/nuttx/nuttx/downloads
    https://bitbucket.org/nuttx/apps/downloads

Both may be needed (see the top-level nuttx/README.txt file for build
information).

Additional new features and extended functionality:

    * Core OS:

      - Kernel Modules:  Module initializer may now return a symbol table.
      - Modules:  Extend the module interface so that we can access symbols
        exported by the module.
      - Shared Libraries:  In the FLAT build mode, kernel modules may be
        used to provide minimal shared library functionality.
      - Modules/Shared Libraries:  Add support for dependencies between
        modules.
      - Module Library:  Add build a configuration logic for a shared module
        library.
      - Shared Libraries: Implement module based shared libraries for the
        PROTECTED mode build.
      - Interrupt handling:  irq_attach() now includes an argument of type
        xcpt_t that retained with the handler address.  That argument is
        then provided to the interrupt handler when the interrupt occurs.
        The common parameter passing replaces the ad hoc parmater passing
        implemented in current drivers.  From Mark Schulte.
      - Adapt many drivers to utilize the IRQ argument feature.
      - All functions that used to return an xcpt_t old handler value, now
        return an int error code.  The oldhandler value is no longer useful
        with the recent changes to the interrupt argument passing.  Some of
        the functions effected include board_button_irq(), arch_phy_irq(),
        STM32 EXTI functions (Alarm, COMP, PVD), GPIO interrupt logic like
        kinetis_pinirq(), stm32_gpiosetevent(), and others.
      - IRQ subsystem:  Add support for smaller interrupt tables as
        described at
        http://www.nuttx.org/doku.php?id=wiki:howtos:smallvectors .  This
        is partially the work of Mark Schulte.

    * File Systems/Block and MTD Drivers

      - Pseudo File System:  Add support for soft links in the top-level
        psuedo file system.
      - Soft links:  Add an implementation of readlink().
      - Add fstat() support.  Implement fstat() method in binfs, romfs,
        unionfs, tmpfs, nxffs, nfx, hostfs, procfs, and smartfs.
      - fstat:  Add fstat() support to FAT.  From Alan Carvalho de Assis.

    * Graphics/Display Drivers:

      - Fonts: Add support for Tom Thumb small mono-space font. From Alan
        Carvalho de Assis.
      - Graphics:  Separated of font cache from graphics/nxterm.  Now in
        libnx/nxfronts where it can be shared with other grapics
        applications.

    * Networking/Network Drivers:

      - Ethernet drivers:  Add framework for serialization in the case where
        multiple low-priority work queues are used.

    * Other Common Device Drivers:

      - Add capabilities() method to SDIO interface.  Remove
        CONFIG_SDIO_WIDTH_D1_ONLY.  That should not be a global propertie,
        but rather a capability/limitation of single slot when there may be
        multiple slots.
      - Removed dmasupported() method from the SDIO interface.  That is now
        a bit in the capability set.
      - drivers/sensors: Add driver for the ST L3GD20 3 axis gyro.  From
        raiden00.

    * Atmel SAM3/4:

      - SAM3/4: Add support for ATSAM4S4C.  From Wolfgang Reißnegger.

    * NXP Freescale i.MX6 Boards:

      - Sabre 6quad:  Enable examples/smp test in i.MX6 SMP/NSH
        configurations.

    * NXP Freescale Kinetis:

      - Kinetis:  Added support for CHIP_MK60FN1M0VLQ12 chip.  From Maciej
        Skrzypek.
      - Kinetis:  Add support for K64/K66 RTC lower half driver. From Neil
        Hancock.
      - Kinetis:  Extensive modification of MCG support based feature
        configuration.  From David Sidrane.
      - Kinetis:  Add support for K66 family.  From David Sidrane.
      - Kinetis:  Created a kinetis SIM versioning scheme pulled in by
        Kinetis chip.h.  From David Sidrane.
      - Created a kinetis PMC versioning scheme pulled in by Kinetis
        chip.h.  From David Sidrane.
      - Kinetis: Extend clock configuration logic.  Refactor
        implementation.  From David Sidrane.

    * NXP Freescale Kinetis Drivers:

      - Kinetis Ethernet:  Kinetis Support RMII clock source select.  This
        defined the RMII clock source select bits and allows the selection
        to be made via Kconfig. From David Sidrane.  Freedom-K66F uses
        ENET_1588_CLKIN as RMII clock
      - Kinetis Serial:  Added configurable 1|2 stop bits.
        HAVE_SERIAL_CONSOLE -> HAVE_UART_CONSOLE to be consistent with
        HAVE_LPUART_CONSOLE naming. From David Sidrane.
      - Kinetis LPserial:  Add LPUART serial driver and Clock
        configuartaion to freedom-k66f board.  From David Sidrane.
      - Kinetis USB device:  Refactor clocking in kinetis_usbdev.  From
        David Sidrane.

    * NXP Freescale Kinetis Boards:

      - Add support for NXP Freedom-k66f development board.  From David
        Sidrane.
      - Kinetis Freedom K66F:  Add Ethernet support.  From David Sidrane.
      - Add twr-k64f120m config.  From Marc Rechté.

    * NXP Freescale LPC43xx Boards:

      - Bamboo-200E: Add netnsh configuration.  From Alan Carvalho de Assis.
      - Add usbnsh config to Bambino 200E board.  From Alan Carvalho de
        Assis.

    * STMicro STM32:

      - STM32 F7: Allow board to configure HSE clock in bypass-mode. This
        is needed to enable HSE with Nucleo-F746ZG board.  From Jussi
        Kivilinna.
      - STM32 F7: stm32_allocateheap: allow use DTCM memory for heap.
        STM32F7 has up to 128KiB of DTCM memory that is currently left
        unused.  This change adds DTCM to main heap if
        CONFIG_STM32F7_DTCMEXCLUDE is not enabled.  From Jussi Kivilinna.
      - Add basic support for the STM32F334.  From Mateusz Szafoni.
      - STM32F33XX DAC, OPAMP, COMP, ADC, HRTIM headers.   From Mateusz
        Szafoni.

    * STMicro STM32 Drivers:

      - STM32 F7 SDMMC:  Add support for single bit operation on SDMMC2.
      - STM32 L4:  Port STM32L4 SAI driver from MDK.
      - STM32 L4:  Bring power management logic from Motrola MDK into NuttX.
      - STM32 L4:  Bring LPTIM driver in from the Motorola MDK.
      - STM32 L4 COMP: Port from Motorola MDK.

    * STMicro STM32 Boards:

      - STM32F429i Discovery: Add support for NxWM on STM32F429i-Disco
        board. From Alan Carvalho de Assis.
      - STM32F103 Minimum: Add support for nRF24 on STM32F103-Minimum
        board. From Alan Carvalho de Assis.
      - Olimex STM32 P407: Add a NSH protected build configuration; Enable
        procfs/ in all configurations.
      - Olimex STM32 P407: Add support for on-board microSD slot.
      - STM32F429i Discovery: add support for the L3GD20 driver.  From
        raiden00.
      - STM32F103 Minimum: Add support to QEncoder on STM32F103 Minimum
        board.   From Alan Carvalho de Assis.
      - Olimex STM32 P407:  Add external SRAM support.
      - Add basic support for the Nucleo F334R8 board.  From Mateusz
        Szafoni.
      - STM32F103 Minimum: Add SDCard support over SPI on STM32F103-Minimum
        board.  From Alan Carvalho de Assis.
      - STM32F103 Minimum: Add support to USB Device on STM32F103-Minimum
        board.  From Alan Carvalho de Assis.

    * C Library/Header Files:

      - compiler.h: packed_struct replaced by begin_packed_struct and
        end_packed_struct. Now support IAR style packed structures.  From
        Aleksandr Vyhovanec.
      - Math library: Leverage optimized ARMv8-M functions from BSD license
        ARM file.
      - Shared libraries:  Add a non-standard dllfnc.h function to set the
        symbol table.
      - C Library: Add a support for setvbuf(). This is a collaborative
        effort.  Alan Carvalho de Assis did the initial prototype.
      - C Library: Add setbuf() which is a trivial wrapper around setvbuf().
      - C library:  Add swab().
      - C library: Add strtoimax and strtoumax.
      - C library:  Add ffs(), rindex(), an index().  Add strings.h.  Move
        strcasecmp, strncasecmp, bzero, bcmp, and bcopy to where they
        belong in strings.h.h, not string.h.  bzero, bcmp, and bcopy are
        legacy functions; the contemporary counterparts should be used
        instead.
      - C library: Add fstatfs().
      - Update cwchar.  Add cwctype.

    * Build/Configuration System:

      - Add configuration support for builds with Ubuntu under Windows 10.

    * Tools:

      - tools/noteinfo.c: A hack tool that I use to analyze some sched_note
        output.  Needs a home and may be useful to others.
      - tools/mkconfig.c: Add logic to keep all of the buffering options in
        sync.

    * NSH: apps/nshlib:

      - NSH: Add support for the 'ln' command.
      - NSH ls command: if node is a symobolic link, use readlink() to get
        and the display the target of the symblic link.
      - NSH: Add readlink command.

    * Applications: apps/examples:

      - apps/examples/nxtext: Make line spacing configurable.
      - apps/system/zmodem/host/nuttx/compiler.h synchronized with
        nuttx/nuttx/include/nuttx/compiler.h.  From Aleksandr Vyhovanec.
      - apps/examples/sotest:  Add a test for shared libraries.
      - apps/examples/ostest:  Add a test of setvbuf().
      - apps/examples/stat:  Add a simple test for stat(), fstat(),
        statfs(), and fstatfs().

Works-In-Progress:

    * IEEE802.14.5/6LowPAN.  Hooks and framework for this effort were
      introduced in NuttX-7.15.  Work has continued on this effort on
      forks from the main repositories, albeit with many interruptions.
      The completion of this wireless feature will postponed until at
      least NuttX-7.21.

Bugfixes.  Only the most critical bugfixes are listed here (see the
ChangeLog for the complete list of bugfixes and for additional, more
detailed bugfix information):

    * Core OS:

      - SMP: There were certain conditions that we must avoid by preventing
        the release of the pending tasks while withn a critical section.
        But this logic was incomplete; there was no logic to prevent other
        CPUs from adding new, running tasks while on CPU is in a critical
        section.  This commit corrects this.  This is matching logic in
        sched_addreadytorun to avoid starting new tasks within the critical
        section (unless the CPU is the holder of the lock).  The holder of
        the IRQ lock must be permitted to do whatever it needs to do.
      - SMP: Make checks for CPU lock set more robust.  There are certain
        conditions early in initialization on during interrupt handling
        where things need to be done a little differently.
      - sched_cpulocked:  Avoid use of spinlock.  That has been reported to
        cause a deadlock (2016-12-28).
      - SMP: Fix a gap where we may try to make modifications to the task
        lists without being in a critical sections.  That permits
        concurrent access to the tasks lists and many subtle problems.
        This fix just remains in the critical section throughout the
        operation (and possible until the task is restore in the event of a
        context switch).  Makes a big difference in stability.
      - SMP: Fix an error in critical section logic when performing a
        context switch from an interrupt handler.  The g_cpu_irqset bit was
        not being set for the CPU so other CPUs did not know about the
        critical section.
      - SMP Signals: Fix some SMP signal delivery logic. Was not handling
        some critical sections correctly and was missing logic to signal
        tasks running on other CPUs.
      - SMP:  Fix timer related issues:  Round robin and sporadic
        scheduling were only being performed for tasks running on the CPU
        that processes the system timer interrupt.  Similary, CPU load
        measurements were only be processed for running on the CPU that
        receives the sampling interrupt.
      - sched_note: Fix spinlock instrumentation.  From Masayuki Ishikawa.
      - In all implementations of _exit(), use enter_critical_section() vs.
        disabling local interrupts.
      - sigtimedwait:  When timer expires, up_unblock_task() is called.
        This is okay in the single CPU case because interrupts are disable
        in the timer interrupt handler.  But it is insufficient in the SMP
        case.  enter_ and leave_critical_section() must be called in order
        to manage spinlocks correctly.
      - Fix a compile error: in sched_cpuload.c:Line136, the variables ts
        and secs are not defined if CONFIG_CPULOAD_ONESHOT_ENTROPY = 0.
        However, these variables are used regardless of
        CONFIG_CPULOAD_ONESHOT_ENTROPY at lines~180:onwards.  From rg.
      - CPU load: Correct computation of the nominal period to use when the
        source is a oneshot timer.
      - Cancellation points:  Fix some backward logic in conditional
        compilation.
      - Remove an unused variable when calling sigwaitinfo() and
        sigtimedwait().  From Masayuki Ishikawa.

    * File System/Block and MTD Drivers:

      - procfs:  Correct to snprintf-related errors in fs_procfsproc.c.
        Resolves issue #24.
      - Add logic to VFS rename:  If target of rename exists and is a
        directory, then the source file should be moved 'under' the target
        directory. POSIX also requires that if the target is a file, then
        that old file must be deleted.
      - Fix open() a block device with
        CONFIG_DISABLE_PSEUDOFS_OPERATIONS=y. From Masayuki Ishikawa.
      - File System: Don't build block driver proxy if PSEUDOFS_OPERATIONS
        are disabled.
      - sendfile():  Fix error introduced with commit
        ff73be870e38959b0aaee5961dc47b4b58dc2d86.  Noted by Maciej Wójcik.

    * Graphics/Graphic Drivers:

      - NxWM configurations.  If using a 7-bit character set, then the
        cursor character cannot be 137 (graphic block).  Use 95
        (underscore) instead.
      - NX server: Correct message queue names.  Should not be at /dev,
        but rather relative to /var/mqueue.

    * Common Drivers:

      - MMCSD_SDIO: Only wait for card ejected if card detection is
        supported. From Alan Carvalho de Assis.
      - Typos withim mtd/ with Macronix MX25L.  In
        NuttX/drivers/mtd/Make.defs letters X between M and 25 are
        missing.  Noted by Oleg Evseev.
      - USBMSC: Always set LUN readonly flag.  From Wolfgang Reißnegger.
      - drivers/lcd:  ssd1306_configspi() must have global scope.
      - MMC/SD SDIO:  Some drivers need to start DMA before sending CMD24
        and some AFTER.  From Alan Carvalho de Assis.
      - drivers/tone.c:  Handle configuration with multiple PWM channels.
        This resolves issue #30: Audio Tone Generator and PWM Multiple
        Output Channel options.
      - drivers/tone.c:  50% duty needs to be expressed a a fixed precision
        number.
      - drivers/spi/Kconfig:  There is too much SPI in the configuration
        menu; SPI Driver Support menu is empty.  From Maciej Wójcik.
      - option to enable Memory Card debug output was hidden with SD cards
        connected through SPI.   From Maciej Wójcik.
      - usbhost_cdcacm: fix tx outbuffer overflow and remove now invalid
        assert.  From Janne Rosberg.

    * Networking/Network Drivers:

      - Networking: Fixed some issues that prevented IPv6 from working with
        IPv4 enabled.  From Pascal Speck.
      - Networking: fixed a nullptr-dereference on iob_clone.  From Pascal
        Speck.
      - Ethernet: Need two work structures (minimum) in all Ethernet
        drivers so that pending poll work is not lost when an interrupt
        occurs.

    * ARMv7-R:

      - I found an issue inside the cp15_coherent_dcache function:  The
        "mcr CP15_BPIALLIS(r0)" should only be used with SMP
        configurationa. In non-SMP configuration this instruction could
        become undefined.  From Manohara HK.

    * Atmel SAM3/4 Drivers:

      - SAM3/4: GPIO bit numbering typo fixes.  From Wolfgang Reißnegger.

    * Atmel SAM3/4 Boards:

      - Add missing sched_note_*() calls in sam4cm SMP functions.

    * NXP/Freescale Kinetis:

      - Kinetis: Fixed wrong MCG VDIV calculation on new NXP K60.  From
        Maciej Skrzypek.
      - Kinetis: Need to set HAVE_UART_DEVICE when UART4 is selected.  From
        Maciej Skrzypek.
      - Kinetis MCG: Wrong FRDIV set in MCG_C1.  From Maciej Skrzypek.

    * NXP/Freescale Kinetis Drivers:

      - Kinetis Serial: Fixed compile error when UART5 is selected.  From
        Maciej Skrzypek.
      - Kinetis SDHC - Enable clock after selected.  From David Sidrane.
      - Kinetis:  Correct some SPI and I2C configuration issues.  From
        David Sidrane.
      - Kinetis Ethernet:  Add #define for number of loops for auto
        negotiation to complete.  From Marc Rechté.
      - Kinetis Werial:  Fixed up_rxint - did not disable the RX
        interuppts. There was an OR where and AND NOT was needed.  From
        David Sidrane.

    * NXP/Freescale LPC43xx:

      - LPC43 pinset definitions:  Add more 1 bit to pinset to reach
        SFSCLK0-SFSCLK3. Remove PINCONFIG_DIGITAL.  From Alan Carvalho de
        Assis.

    * NXP/Freescale LPC43xx Drivers:

      - LPC43 serial:  Correct conditional logic that selects /dev/ttySN.
        Problem noted by Alan Carvalho de Assis.

    * NXP/Freescale i.MX6:

      - i.MX6: Fix clearing GPT status register.  From Masayuki Ishikawa.

    * STMicro STM32:

      - STM32, STM32L4 Oneshot: Fix logic so that it can support multiple
        oneshot timers.
      - STM32 F7: Added missing ARCH_HAVE_RESET for F7.  From David Sidrane.
      - STM32:  Add missing STM32_BKP_BASE.  From David Sidrane.
      - STM32 and STM32F7: Fixes the BKP reference counter issue.  From
        David Sidrane.

    * STMicro STM32 Drivers:

      - Fix for SAMv7 SPI: DLYBS value was calculated, but never written to
        any registers. This led to incorrect timings on the bus.  From
        Michael Spahlinger.
      - STM32 QEncoder: Fix QEncoder driver, based on STM32L4 driver.  From
        Alan Carvalho de Assis.
      - STM32 QEncoder:  Enable clocking to the timer on QE setup; disable
        clock on QE teardown.
      - STM32 Ethernet: Need two work structures so that pending poll work
        is not lost when an interrupt occurs.  This change has also been
        ported to all all other effected Ethernet drivers.
      - STM32 OTGHS host:  stm32_in_transfer() fails and returns NAK if a
        short transfer is received.  This causes problems from class
        drivers like CDC/ACM where short packets are expected.  In those
        protocols, any transfer may be terminated by sending short or NUL
        packet.  From Janne Rosberg.  Adapted Janne Rosberg's patch to
        STM32 OTGHS host to OTGFS host, and to similar USB host
        implementations for STM32 L4 and F7.

    * STMicro STM32 Boards:

      - STM32F4 Discovery: Fix issues with QEncoder support.  From Alan
        Carvalho de Assis.

    * C Library/Header Files:

      - Add debug assertion in libdtoa to catch attempts to use floating
        point output formats from within an interrupt handler.  That will
        cause assertions or crashes downstream because __dtoa will attempt
        to allocate memory.  From Pierre-noel Bouteville.
      - libc: Fix ARMv7-A/R memcpy assembly.
      - Fix return value if x is NaN.  From Aleksandr Vyhovanec.

    * apps/nshlib:

      - NSH: Eliminate a warning when all memory inspection commands are disabled.

    * apps/graphics:

      - apps/graphics/traveler/tools: Fix linkage issue. The -lm should
        come after -o binname.  From Alan Carvalho de Assis.

    * apps/netutils:

      - The CONFIG_NETUTILS_HTTPD_PATH constant is used by httpd_mmap.c and
        httpd_sendfile.c but It was not present in Kconfig menu.  From
        Maciej Wójcik.

    * apps/examples:

      - Configurations that enable OSTEST must not disable signals.
      - apps/examples/ostest:  Was ignoring
        CONFIG_EXAMPLES_OSTEST_FPUTESTDISABLE.
      - In apps/examples/mtdpart/mtdpart_main.c where
        CONFIG_EXAMPLES_MTDPART_NPARTITIONS defining is checked should be
        #ifndef instead of #ifdef.  Noted by Oleg Evseev.

NuttX-7.21 Release Notes
------------------------

The 121st release of NuttX, Version 7.21, was made on June 6, 2017,
and is available for download from the Bitbucket.org website.  Note
that release consists of two tarballs:  nuttx-7.21.tar.gz and
apps-7.21.tar.gz.  These are available from:

    https://bitbucket.org/nuttx/nuttx/downloads
    https://bitbucket.org/nuttx/apps/downloads

Both may be needed (see the top-level nuttx/README.txt file for build
information).

Additional new features and extended functionality:

    * Core OS:

      - pthread rwlocks:  Add an implementation for read/write locks
        (rwlocks) into the pthread library.  These locks are writer
        priority, such that if any writers come in they are given priority
        for writing.  From Mark Schulte.
      - pthread robust mutexes:  Implement robust mutex support:
        pthread_mutex_lock() and trylock() will return EOWNERDEAD if the
        mutex is locked by a thread that no longer exists.  Add
        pthread_mutex_consistent() to recover from this situation.  Keep
        list of all mutexes held by a thread in a list in the pthread's TCB.
        When pthread exits or is cancelled, mutexes held by thread are
        marked inconsistent and the highest priority thread waiting for the
        mutex is awakened.  There is a configuration option to (a) support
        only robust mutexes, (b) support only traditional unsafe mutexes,
        or (c) Support both unsafe and robust mutexes via
        pthread_mutexattr_get/setrobust().
      - pthread cancellation points:  Add logic to disable cancellation
        points within the OS.  This is useful when an internal OS function
        that is NOT a cancellation point calls an OS function which is a
        cancellation point.  In that case, irrecoverable states may occur if
        the cancellation is within the OS. From Juha Niskanen.
      - clock:  Add clock_resynchronize and use subseconds RTC.  Add
        clock_resynchronize for better synchronization of CLOCK_REALTIME and
        CLOCK_MONOTONIC to match RTC after resume from low-power state.  Add
        up_rtc_getdatetime_with_subseconds under
        CONFIG_ARCH_HAVE_RTC_SUBSECONDS to allow initializing (and
        resynchronizing) system clock with subseconds accuracy RTC.  From
        Jussi Kivilinna.
      - clock:  Add new type ssystime_t for relative 64-bit ticks, change
        ticks<->time conversion functions to use ssystime_t.  From Jussi
        Kivilinna.
      - clock:  Add testing for 32-bit overflow of 64-bit system timer.  From
        Jussi Kivilinna.

    * File Systems/Block and MTD Drivers

      - drivers/mtd/w25.c:  Erase sector only if it is not in erased state.
        From Jussi Kivilinna.

    * Graphics/Display Drivers:

      - drivers/lcd:  Extend st7565 driver to include support for the
        AQM_1248A.  From Masayuki Ishikawa.
      - drivers/lcd:  Add driver for Nokia 5110 (Philips PCD8544).  From Alan
        Carvalho de Assis.

    * Networking/Network Drivers:

      - Extensive modifications to support wireless network (see below).
      - TUN driver:  Implement TAP (OSI layer 2) mode. Enable by setting the
        IFF_TAP flag instead of the IFF_TUN flag in ifr_flags.  From Thomas
        Keh.
      - Add user-space networking stack API (usrsock).  User-space
        networking stack API allows user-space daemon to provide TCP/IP
        stack implementation for NuttX network.  Main use for this is to
        allow use and seamless integration of HW-provided TCP/IP stacks to
        NuttX.  For example, user-space daemon can translate /dev/usrsock
        API requests to HW TCP/IP API requests while rest of the user-space
        can access standard socket API, with socket descriptors that can be
        used with NuttX system calls.  From Jussi Kivilinna.
      - net/:  Network driver now retains Ethernet MAC address in a union so
        that other link layer addresses may be used in a MULTILINK
        environment.

    * Wireless Networking/Wireless Drivers:

      - BCM43362:  Support for Broadcom's BCM43362 WiFi chip was contributed
        by Simon Piriou as part of the port of the Particle Photon board.
        Only station functionality is available at present.  This work
        includes not on the WiFi driver, but the support Particle Photon
        board, the infrasture for IEEE 802.11 FullMAC networking including
        the network device interface, WiFi configuration, AP scanning and
        authentication and association with an AP.
      - IEEE 802.11 networking tools and support.
      - IEEE 802.15.4 MAC support.  This is an effort that was started some
        time back by Sebastien Lorquet (with some help from Matte Poppe).
        Recently, Anthony Merlino has taken on this effort and has made
        some significant progress.  Using the Microchip MRF24J40 module with
        the Mikroe Clicker2-STM32 board along with a PC-based IEEE 802.15.4
        sniffer, Anthonly has verified correct transmittion and receipt of
        basic frames.
      - Microchip MRF24J40: As mentioned above, this IEEE 802.15.4 radio
        driver is now basically functional.
      - IEEE 802.15.4 Network Driver:  A driver that interfaces the NuttX
        network with the IEEE 802.15.4 MAC has been developed but is still
        incomplete and has not been verified.
      - IEEE 802.15.4 Network Loopback Driver:  A simple IEEE 802.15.4 MAC
        loopback driver was developed.  This driver allowed for parallel
        development of the IEEE 802.15.4 MAC and 6loWPAN.
      - 6loWPAN:  The Contiki 6loWPAN stack has been ported so that works
        within the NuttX networking framework and interfaces with the new
        IEEE 802.15.4 MAC via the network driver.  Live testing with
        IEEE 802.15.4 radios has not yet been done; all testing has used
        the loopback driver.  There are no known problems and the stack
        is ready for additional testing.
      - Add option to enable wireless debug output.

    * Other Common Device Drivers:

      - Add entropy pool and strong random number generator.   Entropy pool
        gathers environmental noise from device drivers, user-space, etc.,
        and returns good random numbers, suitable for cryptographic use.
        Based on entropy pool design from *BSDs and uses BLAKE2Xs algorithm
        for CSPRNG output.  Patch also adds /dev/urandom support for using
        entropy pool RNG and new 'getrandom' system call for getting
        randomness without file-descriptor usage (thus avoiding file-
        descriptor exhaustion attacks). The 'getrandom' interface is similar
        as 'getentropy' and 'getrandom' available on OpenBSD and Linux
        respectively.  From Jussi Kivilinna.
      - XBox One controller:  Adds USB host driver support for the XBox One
        controller.  Currently only the latest version (XBox One X)
        controller works.  The older XBox One controllers do not enumerate
        correctly.  From Brian Webb.
      - drivers/analog:  Add basic COMP driver.  From Mateusz Szafoni.
      - drivers/analog:  Add driver for the LTC1767L ADC.  From Martin
        Lederhilger.
      - drivers/analog:  Add basic OPAMP driver.  From Mateusz Szafoni.
      - drivers/sensors:  Add driver for ST HTS221 humidity sensor.  From
        Juha Niskanen.
      - drivers/sensors:  Add driver for ST LPS25H pressure sensor.  From
        Juha Niskanen.
      - drivers/sensors:  Add driver for ST LIS2DH accelerometer.  From Timo
        Voutilainen.
      - drivers/usbmisc:  Add driver for Fairchild FUSB301 USB type-C
        controller.  From Harri Luhtala.
      - RTC:  Add interface for check if RTC time has been set.  New
        interface allows checking if RTC time has been set.  This allows to
        application to detect if RTC has valid time (after reset) or should
        application attempt to get real time by other means (for example, by
        launching ntpclient or GPS).  From Jussi Kivilinna.
      - Buttons:  Change return value of board_buttons() and the type of
        btn_buttonset_t to uint32_t so that more than 8 buttons can be
        supported.
      - drivers/syslog:  Use monotonic clock for timestamp when available.
        From Jussi Kivilinna.
      - SPI:  Add an instance argument to the SPIDEV definitions.  Thus,
        instead of specifying a FLASH device, for example, as SPI_FLASH, you
        would now use SPI_FLASH(0) where the "instance" argument now
        distinguishes multiple FLASH devices on the same SPI bus.  From
        Sebastien Lorquet.
      - IOBs:  Move from net/iob to a better location in mm/iob where they
        can be shared outside of the networking logic.  Current also used
        by IEEE 802.15.4 MAC and by syslog (when buffering enabled).
      - syslog:  Add option to buffer SYSLOG output to avoid interleaving.
        Uses new shareable IOBs.  Additional logic to assure that the the
        write from the buffer is a single atomic write in normal debug
        output.
      - drivers/can:  Move CAN subsystem to its own directory and put device
        drivers there.  From Alan Carvalho de Assis.
      - drivers/can:  Add Microchip MCP2515 CAN Bus controller driver.  From
        Alan Carvalho de Assis.
      - drivers/audio:  Add cs43l22 audio driver.  From Taras Drozdovsky.
      - drivers/input:  Add Cypress MBR3108 CapSense touch button driver.
        From Juha Niskanen.

    * Simulation

      - configs/sim/sixlowpan:  Configuration for testing the 6loWPAN with
        the IEEE 802.15.4 loopback network driver.

    * Infineon XMC4xxx:

      - arch/arm/src/xmc4:  Initial, partial support for Infineon XMC4xxx.

    * Infineon XMC4xxx Boards:

      - XMC4500 Relax:  Add basic board support infrastructure of Infineon
        XMC4500 Relax Lite v1.  Basic serial, LED, and button button support
        for a simple NSH configuration.  There are still stome remaining
        issues with serial communications.

    * MicroChip PIC32MX Boards:

      - pic32mx7mmb:  Add support for the Pinquino toolchain.
      - pic32mx7mmb:  Add support for PROCFS file system.

    * NXP Freescale Kinetis:

      - Kinetis:  Allow board to add pullups on SDHC lines.  From David
        Sidrane.
      - Kinetis:  Use optional BOARD_OSC_CR and BOARD_OSC_DIV in clock
        configuration.  From David Sidrane.

    * NXP Freescale Kinetis Drivers:

      - Kinetis:  Add Timer PWM Module (TPM) to K66 chip.  From David
        Sidrane.
      - Kinetis:  Added HW flow control and termios.  From David Sidrane.
      - Kinetis:  Add ARCH_HAVE_I2CRESET.  From David Sidrane.

    * NXP Freescale LPC43xx:

      - Add support for LPC4337FET256.  From Andreas Bihlmaier.

    * STMicro STM32:

      - Change STM32 tickless to use only one timer.  From Konstantin
        Berezenko.
      - STM32 F7:  Add support for LSE RTC and enable RTC subseconds.  From
        Jussi Kivilinna.
      - STM32 L1: stm32l15xx_rcc:  Add support for using MSI as system
        clock. From Juha Niskanen.
      - STM32 L1:  stm32l15xxx_rcc: configure medium performance voltage
        range and zero wait-state when allowed by SYSCLK setting.  Zero
        wait-state for flash can be configured when:  (1) Range 1 and
        SYSCLK <= 16 Mhz, (2) Range 2 and SYSCLK <= 8 Mhz, or (3) Range 3
        and SYSCLK <= 4.2 Mhz.  Medium performance voltage range (1.5V)
        can be configured when SYSCLK is up to 16 Mhz and PLLVCO up to
        48 Mhz.  From Juha Niskanen.
      - STM32 F0: Add basic support for STM32F0.  From Alan Carvalho de
        Assis.
      - STM32 F0:  Add basic support for STM32F07x family.
      - STM32 L1: stm32l15xx_rcc: Allow board to configure HSE clock in
        bypass-mode.  Allows using MCO output from ST-link chip (on Nucleo
        and Discovery boards) as HSE input.  From Juha Niskanen.
      - STM32 L1: Add support for STM32L152CC, STM32L152RC and STM32L152VC.
        From Juha Niskanen.
      - STM32 F0:  Add support for HSI48.
      - STM32 L4:  Add support for the STM32L496XX family.  From Juha
        Niskanen.
      - STM32 L4: modularize Kconfig to support different product
        lines/families.  This is modeled after STM32F7. Idea is to declare
        each chip in Kconfig but allow for flash size override.  Commit adds
        many STM32L4_HAVE_XXX feature test macros.  From Juha Niskanen.
      - STM32 L4:  Separate SYSCFG into product line specific files for
        clarity.  From Juha Niskanen.
      - STM32 L4:  Add support for many new MCUs from the STM32L4X3XX
        product line.  From Juha Niskanen.
      - STM32 L4:  Add dbgmcu header files.  From Juha Niskanen.
      - STM32 F410:  Add support for STM32F410.  STM32F410 is a version of
        STM32F4 with 32 KB of RAM and 62 or 128 KB of flash.  From Gwenhael
        Goavec-Merou.

    * STMicro STM32 Drivers:

      - SDIO:  Extensions to support the SDIO interface to the BCM43362 from
        Simon Piriou.
      - STM32 F2:  Add USB OTG HS support for stm32f20xxx cores.  From Simon
        Piriou.
      - STM32 F2, F4, and F7:  Add BOARD_DISABLE_USBOTG_HSULPI flag.  From
        Simon Piriou.
      - STM32 F33:  Move DMA logic to a separate files + add ADC support.
        From Mateusz Szafoni.
      - STM32 F3:  Add COMP support.  From Mateusz Szafoni.
      - STM32 F33:  Support for COMP character driver.  From Mateusz Szafoni.
      - STM32 F4:  Implement DMA support for the STM32F4 I2C.  From rg.
      - STM32 F7:  Add stm32 RNG support.  This is copied from stm32l4.
        Tested on STM32F746ZG board.  From Juha Niskanen.
      - STM32 L1:  Add STM32L162VE to chip.h.  From Juha Niskanen.
      - STM32 F4:  Add I2C3 SDA pin mapping for STM32F411.  From no1wudi.
      - STM32 L1:  stm32_flash:  Add EEPROM writing for STM32L15XX.  From
        Juha Niskanen.
      - STM32 F7:  Serial:  Add interface to get uart_dev_t by USART number,
        stm32_serial_get_uart.  From Jussi Kivilinna.
      - STM32 F4:  Provide TIM5 definition for STM32F429.  From Matias v01d.
      - STM32 F0:  Add an untested port of the F1 USB device to the STM32F0.
      - STM32 F0:  Add support for the STM32F09X family.  From Juha
        Niskanen.
      - STM32 F0:  Initial cut at I2C driver.  Still a work in progress.
        From Alan Carvalho de Assis.
      - STM32 F33:  Add OPAMP support.  From Mateusz Szafoni.
      - STM32 L4: stm32l4_i2c:  Add I2C4 code.  From Juha Niskanen.
      - STM32 L4:  Add GPIO_PORTI definition.  From Juha Niskanen.
      - STM32 F7 Serial:  Allow configuring Rx DMA buffer size.  From Jussi
        Kivilinna.
      - STM32 L4:  Firewall for stm32l4x3xx.  Not tested for any product
        family, but now it at least compiles.  L496 devices can have one bit
        wider Volatile Data Segment.  From Juha Niskanen.
      - STM32 TIM:  Add method to get timer width.  Freerun timer: Use timer
        width to get the correct clock rollover point.
      - STM32 L4:  Add internal flash write support.  From Juha Niskanen.
      - STM32 L4:  Port stm32l4_serial_get_uart function from STM32F7.  From
        Juha Niskanen.
      - STM32 Ethernet:  Add support for KSZ8081 PHY interrupts.  From
        Sebastien Lorquet.
      - STM32 F4:  Add I2S driver.  From Taras Drozdovsky.
      - STM32 L4:  Add IWDG peripheral.  This is the same as for STM32
        except that prescale and reload can be changed after watchdog has
        been started, as this seems to work on L4.  From Juha Niskanen.
      - STM32 F7:  Add SPI DMA support.  From Jussi Kivilinna.

    * STMicro STM32 Boards:

      - Support for the Particle Photon board was contributed by Simon
        Piriou.  The Photon board is based on a STM32F205G MCU with and on-
        board BCM43362 WiFi chip that interfaces via the STM32's SDIO
        interface.  Board configuration support includes, in addition,
        buttons, LEDS, IWDG, USB OTG HS, and procfs support.  Configurations
        available for nsh, usbnsh, and wlan configurations.
      - Clicker2-STM32:  Support for the Mikroelektronika Clicker 2 for
        STM32 was added by Anthony Merlino.  This board, along with the
        MRF24J40 Click board is the platform used to deveop the IEEE
        802.15.4 support.  The boad configuration includes the MRF24J40
        intialization logic and SPI support.  Configurations exist for nsh,
        knsh, usbnsh, and mrf24j40-radio.
      - Nucleo_F334R8:  Add ADC example.  From Mateusz Szafoni.
      - Nucleo-F334R8:  Add COMP support.  From Mateusz Szafoni.
      - Nucleo-F334R8:  Use new COMP driver.  From Mateusz Szafoni.
      - Adds USB host support to stm32f411-disco board.  From Brian Webb.
      - Add stm32f0discovery board support.  From Alan Carvalho de Assis.
      - Nucleo-F072RB:  Add board configuration.
      - Nucleo-F334R8:  Add OPAMP support.  From Mateusz Szafoni.
      - Nucleo-F072RB:  Add support for the I2C driver used by I2C tools.
      - Nucleo-L496ZG:  Add nucleo-l496zg board files.  From Juha Niskanen.
      - Nucleo-F091RC:  Add nucleo-f091rc board files.  From Juha Niskanen.
      - Nucleo-L432KC:  Add nucleo-l432kc board files.  From Sebastien
        Lorquet.
      - Nucleo-L452RE:  Add nucleo-l452re board files.  From Juha Niskanen.
      - stm32f103-miniumum:  Add board support to use the Nokia 5110
        LCD display driver.  From Alan Carvalho de Assis.

    * C Library/Header Files:

      - C library:  Add strerror_r().
      - C Library:  Add wcstoull(), swprintf(), wcstod(), wcstof(), wcstol(),
        wcstold(), wcstoul(), wcstoll() functions.  Add mbsnrtowcs() and
        wcsnrtombs() (just returning success).  Add mbtowc() and wctomb() to
        C++ std namespace.  From Alan Carvalho de Assis.
      - C Library:  Add ffsl(), ffsll(), fls(), flsl(), flsll() and use
        GCC's __builtin_ctz/__builtin_clz for faster implementation of these.
        From Jussi Kivilinna.
      - fixedmath:  Add square root and b32_t conversion operators.  From
        Jussi Kivilinna.
      - locale.h:  Add a bogus definition of locale_t.
      - C library:  Versions mbrlen and mbsrtowcs taken and adapted from
        FreeBSD code (at https://github.com/freebsd/freebsd/).  From Matias
        v01d.

    * Build/Configuration System:

      - Include C++ library in 'make export'.  From Alan Carvalho de Assis.
      - configs:  Remove all setenv.sh and setenv.bat files.  Remove all
        references to setenv.sh and setenv.bat from all config README files.
      - Kconfig/deconfigs:  Add CONFIG_ARCH_TOOLCHAIN_GNU to indicate that
        the toolchain is based on GNU gcc/as/ld.  This is in addition to the
        CPU-specific versions of the same definition.
      - Move prototype for up_cxxinitialize() from nuttx/include/nuttx/arch.h
        to apps/include/platform/cxxinitialize.h.

    * Tools:

      - Add initialconfig.c so that perhaps in the future we will be able to
        use this to generate a new configuration from scratch (rather than
        having to derive new configurations from existing configurations).
        NOTE: Not yet intregated into the build system.

    * NSH: apps/nshlib:

      - Added support for set [{+|-}{e|x|xe|ex}] [<name> <value>].  Set the
        'exit on error control' and/or 'print a trace' of commands when
        parsing scripts in NSH.  The settinngs are in effect from the point
        of exection, until they are changed again, or in the case of the init
        script, the settings are returned to the default settings when it
        exits.  Included child scripts will run with the parents settings and
        changes made in the child script will effect the parent on return.
        Use 'set -e' to enable and 'set +e' to disable (ignore) the exit
        condition on commands. The default is -e. Errors cause script to
        exit.  Use 'set -x' to enable and 'set +x' to disable (silence)
        printing a trace of the script commands as they are ececuted. The
        default is +x. No printing of a trace of script commands as they are
        executed.  From David Sidrane.
      - Print expanded variables if -x.  From David Sidrane.
      - ifconfig command:  Extend ifconfig to support 6loWPAN.  Adapt to
        some changes in configuration variable usage.
      - Network initialization:  If IEEE802.11 selected use wlan0 instead of
        eth0 for network device name.
      - Network initialization:  NSH now has configuration options to select
        the wireless properties.  It builds the configuration structure and
        passes this to wpa_driver_wext_associate() so that it will set the
        network as configured.
      - Network initialization:  Add a new option CONFIG_NSH_NETLOCAL that
        will suppress some built in operations and will support manual
        configuration of a wireless network through command line tools.

    * Examples/Tests: apps/examples:

      - examples/xbc_text: Adds a test program for the XBox One controller
        driver.  From Brian Webb.
      - examples/ostest:  Add a test of robust mutexes.
      - examples/ostest: Add tests for pthread_rwlock.  Adding tests to be
        used to verify the pthread_rwlock lock works.  From Mark Schulte.
      - examples/ostest:  Additional test for rwlock and one for cancel
        cleanup handlers.  From Juha Niskanen.
      - examples/usrsocktest:  Add application for USRSOCK testing.  From
        Jussi Kivilinna.
      - examples/nettest:  Adapt for use in testing 6loWPAN.
      - examples/nettest:  If doing loopback, but not using the official
        loopback device, then use the server should use the configured client
        IP address.
      - examples/udpblaster:  Several fixes to work with 6loWPAN.
      - examples/udpblaster:  Add logic to bind the local UDP socket to a
        well-known address.
      - examples/configdata:  Add stacksize and priority.  From Juha Niskanen.

    * Network Utilies: apps/netuils:

      - netutils/netlib:  Add IEEE 802.11 wireless IOCTL wrappers.
      - netutils/netlib: Add a helper function to convert a string to a
        6loWPAN node address.
      - netlib and NSH: Add logic to get/set the IEEE802.15.4 PAN ID.
      - netutils/dhcpc:  Make the network device name a configuration
        option.  Was hardcoded to eth0 but may, instead, need to be wlan0.
      - netutils/dhcpc:  Remove hard-coded interface device.  Now passed as
        a parameter to dhcpc_open().  From Sebastien Lorquet.

    * Wireless Utilies: apps/wireless:

      - wireless/wapi:   Port of Wapi wireless services.  The original
        depended on features not supported by NuttX:  Removed logic that
        depends on Linux netlink.  Removed functionality that depended on
        the Linux procfs:  This includes only 1) listing of available
        interfaces and 2) listing of all routes.
      - wireless/wapi:  Create command line Wapi application based on
        Wapi sample code.
      - wireless/wapi:  wpa_driver_wext_associate() now accepts a
        configuration parameter that can be used to specify the wireless
        properties.
      - wireless/wapi:  Add basic wapi_event_stream_extract implementation.
        From Simon Piriou.
      - wireless/ieee802154:  Add iwpan and i8sak tools.  iwpan is similar
        in concept to wapi.  From Anthony Merlino (i8sak was originally
        by Sebastien Lorquet).
      - wireless/ieee802154/libmac:  IEEE 802.15.4 MAC library.
      - wireless/wext:  Add drivers_wext from the WPA supplicant; Integrate
        into NSH.  From Simon Piriou.

    * System Unitilities (apps/system)

      - apps/system/dhcpc:  Add a command to renew or establish a lease on an
        IPv4 address.
      - apps/system/ntpc:  Add a command to start or stop the NTPC daemon.
      - apps/system/ramtest: Make stacksize and priority conigurable.

    * Platform-Specific Support (apps/platform)