configs/z80sim and xtrs:  Serial driver lower halfs ioctl methods should return a negated errno value, not set the errno variable.

    drivers/wireless:  CC1101 driver not permitted to set errno.

    drivers/sensors:  LIS331DL driver not permitted to set errno.

    drivers/lcd: ILI9341 initialize method not permitted to set errno,

    drivers/serial: 16550 UART driver IOCTL method must not set errno; it must return a negated errno value.

    STM32, STM32 F7:  LTDC and DMA2D drivers are not permitted to set the errno.

    SIM LPC31xx:  Serial and console drivers are not permitted to set the errno.

    SAMv7, STM32, STM32 L4:  DAC and ADC drivers are not permitted to set the errno.

    psock_close() and net_close() are internal OS functions and should not set the errno variable.

    psock_ioctl() and netdev_ioctl() are internal OS functions and should not set the errno variable.

    net_dupsd() and net_dupsd2() are internal OS functions and should not set the errno variable.

    net/ and fs/: net_vfcntl(), file_fcntl(), file_dup(), and file_dup2() are all internal OS interfaces and should not modify the errno value.

    net/: psock_recvfrom() is an internal interface and should not set the errno nor should it be a cancellation point.

    net/: psock_accept() is not a cancellation point.

    net/: psock_getsockopt() and psock_socket*9 are an internal interfaces and should not set the errno.

    net/: psock_getsockopt() is an internal interface and should not set the errno.

    net/: psock_listen() is an internal interface and should not set the errno.

    net/: psock_connect(( is an internal interface and should not set the errno nor should it be a cancellation point.

    net/: psock_bind() is an internal interface and should not set the errno.

    net/: psock_accept() is an internal interface and should not set the errno.

net/: Versions of psock_send() and pock_sendto() should not set errno.  That is taken care of at a higher level in the send()/sendto() implementation as appropriate.

syslog_console.c: fix typo

Approved-by: Gregory Nutt <gnutt@nuttx.org>

drivers/syslog:  syslog internal functions should not set the errno variable:  ramlog_putc(), syslog_dev_putc(), syslog_dev_write(), syslog_force().

fs/vfs:null check for path on open and buf on write

Null path check is depend on CONFIG_DEBUG_FEATURES and CONFIG_DEBUG_ASSERTIONS, added null checking so it's always performed
Added null checking on buf for write()

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Add support for an in-memory routing table cache in order to improve performance when the routing table is retained in a file.  The cache holds the most recently used routing table entries and so can eliminate some file access.

Squashed commit of the following:

    net/route:  Flush in cache when any entry is deleted from the routing table.  When a router matching an IP address is found, add the routing table entry to the cache.

    net/route:  Add utility functions to manage an in-memory cache to improve performance when use a file-based routing table.

This commit adds support for routing tables in files in a file system.  This might be useful for customized, per-unit routing tables.

There are two issues with it however:

1. Reading from file system on a per packet basis could be slow.  I think it probably should have a small, in-memory cache of most frequently used routes for good problem.

2. Currently the delroute logic is disabled due to a problem with the design.  NuttX does not currently support truncate().  Therefore, it is not possible to delete entries from the routing table file.

In this current implementation, that leaves the last entry intact at the end of the file.  An alternative design might include a tag on each record to indicate if the record is valid or not.  That would work but would add complexity to the other routing table functions.

The existing implementation is available for testing purposes only if CONFIG_EXPERIMENTAL=y.

Squashed commit of the following:

    net/route:  The current delroute design depends on file truncation.  However, NuttX does not currently support truncate.  Alternative, more complex designs are possible but not implemented.  At present the file routing table are otherwise functional but the delroute logic is disabled via CONFIG_EXPERIMENTAL.  Enable it only if you plan to fix it.

    net/route:  Fix some issues with locking routing table files.

    net/route:  Add partial implementation of delroute for the case where the routing table is in a file.

    net/route:  Add support for seeking to positions in the routing table.

    net/route: Add net_addroute_ipv4/6() using a file-based routing table.

    net/route: Add net_foreach_ipv4/4() using a file-based routing table.

    net/route:  Initial build, configuration, and fs utilies to support routing tables in a file.

STM32L4 FLASH, DFSDM: option bytes, JEXTSEL bits, ADC1 output to DFSDM chips change

* STM32L4 FLASH: add function for modifying device option bytes

* STM32L4 DFSDM: add JEXTSEL bits, ADC1 output to DFSDM chips change

    ST's documentation hints that ADC output can be routed to DFSDM
    on some STM32L4X3 chips, but I got confirmation from tech support
    that this is just a documentation error so remove this from Kconfig.

Approved-by: Gregory Nutt <gnutt@nuttx.org>

fs/vfs:  file_write() and file_pwrite() are internal OS interfaces and should not report errors via the errno

Addes support for read-only routing tables.  Prior to this change, routing tables were only support in RAM and had to be initialized with explicit logic to add the necessary routes to the routing table.  With this change, routes may be defined in the pre-initialized, read-only routing table provided by the board-specific logic

This would be particularly useful, for example, in the case where there is only a single network adaptor and you want all output packets to go to the single adaptor in all cases.  So for that behavior you could add a read-only routing table to the board-specific long that contains a single entry, the default route: 0.0.0.0/0.

Squashed commit of the following:

    net/route:  RAM and ROM routing tables build correctly in all IPv4 and IPv6 configurations.

    net/route: Verify IPv6 ROM route build; Make number of ROM routes a variable, not a configuration item.

    net/route:  Add initial support for ROM-base, read-only routing tables.

    net/route:  Adjust and generalize some structures, rename some functions, and add configuration and build support that will eventually support read-only routing tables.

    net/route:  Some initial though experiments on use of a fixe, read-only routing table

STM32 PWR:  Adds stm32_pwr_getsbf and stm32_pwr_getwuf functions that return the standby flag and the wakeup flag PWR power control/status register.

ROMFS for STM32F4 Discovery board

Approved-by: Gregory Nutt <gnutt@nuttx.org>

Fixed directory unlocking in tmpfs_opendir

Approved-by: Gregory Nutt <gnutt@nuttx.org>

drivers/usbdev/cdcacm.c:  Change ordering of some operations to avoid races; Add missing uppder watermark logic that is normally in serial_io.c but must be duplicated in cdcacm.c; update comments

drivers/usbdev/cdcacm.c:  Fix confusion between flow control being enabled and being active.  Different things

drivers/usbdev/cdcacm.c:  Add some missing logic when flow control is disabled.  Also make sure that the flowcontrol and rxint can handle being re-entered when cdcacm_release_rxpending() is called.

Build break fix: define PWM_TIM2_CH1CFG for channel 1 PWM

Approved-by: Gregory Nutt <gnutt@nuttx.org>

drivers/usbdev/cdcacm.c:  Add a failsafe time to assure that the RX pending queue cannot stall indefinitely.  I can imagine a corner case where the serial driver's RX buffer is full and it stops accepting data and where all of the read requests are queued and there is not event to restart RX processing.  I am not sure that that scenario can really happen, but the failsafe timer gives me peace of mind.

    drivers/usbdev/cdcacm.c:  Change design for queuing RX packets that cannot be processed.  Previous design had a logic problem that could cause data loss.

    drivers/usbdev/cdcacm:  Fixes one of two know design issues.

    drivers/usbdev/cdcacm:  First attempt to plug data leak in input flow control design.  Still missing a few things.