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NuttX TODO List (Last updated January 3, 2012)
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This file summarizes known NuttX bugs, limitations, inconsistencies with
standards, things that could be improved, and ideas for enhancements.
(1) Memory Managment (mm/)
(2) USB (drivers/usbdev, drivers/usbhost)
(10) File system/Generic drivers (fs/, drivers/)
(1) Graphics subystem (graphics/)
(2) ARM/i.MX (arch/arm/src/imx/)
(3) ARM/LM3S6918 (arch/arm/src/lm3s/)
(1) Hitachi/Renesas SH-1 (arch/sh/src/sh1)
apps/
(5) Network Utilities (apps/netutils/)
(5) NuttShell (NSH) (apps/nshlib)
(5) Other Applications & Tests (apps/examples/)
Title: CHILD PTHREAD TERMINATION
Description: When a tasks exits, shouldn't all of its child pthreads also be
terminated?
Status: Open
Priority: Medium, required for good emulation of process/pthread model.
Title: MULTIPLE ATEXIT() FUNCTIONS
Description: atexit() supports registration of only single function called on
exit(). It should support multiple functions registered by atexit()
or onexit() and these should be called in reverse order of
registration when the task exits.
Priority: Low
Description: Implement sys/mman.h and functions
Status: Open
Priority: Low
Description: Implement sys/wait.h and functions. Consider implementing wait,
waitpid, waitid. At present, a parent has no information about
child tasks.
Update: A simple but usable version of waitpid() has been included.
This version is not compliant with all specifications and can be
enabled with CONFIG_SCHED_WAITPID.
Description: Several APIs do not set errno. Need to review all APIs.
Status: Open
Priority: Medium, required for standard compliance (but makes the
code bigger)
Title: TICKLESS OS
Description: On a side note, I have thought about a tick-less timer for the OS
for a long time. Basically we could replace the periodic system
timer interrupt with a one-shot interval timer programmed for the
next interesting event time. That is one way to both reduce the
timer interrupt overhead and also to increase the accuracy of
delays.
Current timer processing is in sched/sched_processtimer.c:
1) Calls clock_timer() which just increments a counter (the system
timer -- basically "up-time"). This is only used when code asks
for the current time. In a tickless OS, some substitute answer
for the question "What time is it?" would need to be developed.
You could use an RTC? Or maybe logic that gets the time until the
next interval expiration and computes the current time. The
solution is not too difficult, but depends on a hardware solution.
2) Calls wd_timer() which handles the link list of ordered events:
Each timer event is saved with the delta time to the next event
in the list. So an interval timer would be perfect to implement this.
3) sched_process_timeslice(). Then there is round-robin time-slicing.
o On-demand paging (sched/)
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Title: ON-DEMAND PAGE INCOMPLETE
Description: On-demand paging has recently been incorporated into the RTOS.
The design of this feature is described here:
http://www.nuttx.org/NuttXDemandPaging.html.
As of this writing, the basic feature implementation is
complete and much of the logic has been verified. The test
harness for the feature exists only for the NXP LPC3131 (see
configs/ea3131/pgnsh and locked directories). There are
some limitations of this testing so I still cannot say that
the feature is fully functional.
Description: get_environ_ptr() (sched/sched_getenvironptr.c) is not implemented.
The representation of the the environment strings selected for
NutX is not compatible with the operation. Some significant
re-design would be required to implement this funcion and that
effort is thought to be not worth the result.
Status: Open
Priority: Low -- There is no plan to implement this.
Description: timer_getoverrun() (sched/timer_getoverrun.c) is not implemented.
Status: Open
Priority: Low -- There is no plan to implement this.
Title: FREE MEMORY ON TASK EXIT
Description: Add an option to free all memory allocated by a task when the
task exits. This is probably not be worth the overhead for a
deeply embedded system.
There would be complexities with this implementation as well
because often one task allocates memory and then passes the
memory to another: The task that "owns" the memory may not
be the same as the task that allocated the memory.
Status: Open
Priority: Medium/Low, a good feature to prevent memory leaks but would
have negative impact on memory usage and code size.
o Signals (sched/, arch/)
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Description: 'Standard' signals and signal actions are not supported.
(e.g., SIGINT, SIGCHLD, SIGSEGV, etc).
Status: Open
Priority: Low, required by standards but not so critical for an
embedded system.
Description: sig_notify() logic does not support SIGEV_THREAD; structure
struct sigevent does not provide required members sigev_notify_function
or sigev_notify_attributes.
Status: Low, there are alternative designs. However, these features
are required by the POSIX standard.
Priority: Low for now
Description: pthread_cancel(): Should implement cancellation points and
pthread_testcancel()
Status: Open
Priority: Low, probably not that useful
Title: USE OF SIZE_T IN NEW OPERATOR
Description: The argument of the 'new' operators should take a type of
size_t (see libxx/libxx_new.cxx and libxx/libxx_newa.cxx). But
size_t has an unknown underlying. In the nuttx sys/types.h
header file, size_t is typed as uint32_t (which is determined by
architecture-specific logic). But the C++ compiler may believe
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