path: root/nuttx/TODO

NuttX TODO List (Last updated August 8, 2009)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  (5)  Task/Scheduler (sched/)
  (2)  Memory Managment (mm/)
  (1)  Signals (sched/, arch/)
  (1)  pthreads (sched/)
  (1)  C++ Support
  (5)  Binary loaders (binfmt/)
 (15)  Network (net/, netutils/)
  (1)  USB (drivers/usbdev)
  (4)  Libraries (lib/)
  (8)  File system/Generic drivers (fs/, drivers/)
  (2)  Graphics subystem (graphics/)
  (1)  Pascal add-on (pcode/)
  (1)  Documentation (Documentation/)
  (6)  Build system / Toolchains
  (3)  NuttShell (NSH) (examples/nsh)
  (3)  Other Applications & Tests (examples/)
  (2)  Linux/Cywgin simulation (arch/sim)
  (3)  ARM (arch/arm/)
  (1)  ARM/C5471 (arch/arm/src/c5471/)
  (3)  ARM/DM320 (arch/arm/src/dm320/)
  (2)  ARM/i.MX (arch/arm/src/imx/)
  (8)  ARM/LPC214x (arch/arm/src/lpc214x/)
  (3)  ARM/STR71x (arch/arm/src/str71x/)
  (3)  ARM/LM3S6918 (arch/arm/src/lm3s/)
  (4)  pjrc-8052 / MCS51 (arch/pjrc-8051/)
  (2)  Hitachi/Renesas SH-1 (arch/sh/src/sh1)
  (4)  Renesas M16C/26 (arch/sh/src/m16c)
  (8)  z80/z8/ez80 (arch/z80/)
  (8)  z16 (arch/z16/)

o Task/Scheduler (sched/)
  ^^^^^^^^^^^^^^^^^^^^^^^

  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.

  Description: atexit() supports registration of one function called on exit().
               Should task_delete() also cause atexit() function to be called?
  Status:      Open
  Priority:    Low, task_delete() is non-standard and its behavior is
               unspecified.

  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.
  Status:      Open
  Priority:    Low

  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)

o Memory Managment (mm/)
  ^^^^^^^^^^^^^^^^^^^^^^

  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.
  Status:      Open
  Priority:    Medium/Low, a good feature to prevent memory leaks but would
               have negative impact on memory usage and code size.

  Description: Current logic adapts size_t for 16-bit address machines vs.
               32-bit address machines.  But a small memory option should also
               be provided so that the small offset option can be used with
               32-bit machines that have small RAM memories (like the lpc2148)
  Status:      Open
  Priority:    High, a good feature enhancement.

o Signals (sched/, arch/)
  ^^^^^^^^^^^^^^^^^^^^^^^

  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.

o pthreads (sched/)
  ^^^^^^^^^^^^^^^^^

  Description: pthread_cancel():  Should implement cancellation points and
               pthread_testcancel()
  Status:      Open
  Priority:    Low, probably not that useful

o C++ Support
  ^^^^^^^^^^^

  Description: Need to call static constructors
  Status:      Open
  Priority:    Low, depends on toolchain.  Call to gcc's built-in static
               constructor logic will probably have to be performed by
               user logic in user_start().

o Binary loaders (binfmt/)
  ^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Not all of the NXFLAT test under examples/nxflat are working.
               Most simply do not compile yet.  tests/mutex runs okay but
               outputs garbage on completion.
  Status:      Open
  Priority:    High

  Description: The ARM up_getpicbase() does not seem to work.  This means
               the some features like wdog's might not work in NXFLAT modules.
  Status:      Open
  Priority:    Medium-High

  Description: At present, all .rodata must be put into RAM.  There is a 
               tentative design change that might allow .rodata to be placed
               in FLASH (see Documentation/NuttXNxFlat.html).
  Status:      Open
  Priority:    Medium

  Description: If the function pointer to a statically defined function is
               taken, then GCC generates a relocation that cannot be handled
               by NXFLAT.  There is a solution described in Documentataion/NuttXNxFlat.html,
               by that would require a compiler change (which we want to avoid).
               The simple workaround is to make such functions global in scope.
  Status:      Open
  Priority:    Low (probably will not fix)

  Description: In the NXFLAT symbol tables... Using a 32-bit hash value instead
               of a string to identify a symbol should result in a smaller footprint.
  Status:      Open
  Priority:    Low

o Network (net/, netutils/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: One critical part of netutils/ apps is untested: The uIP
               resolver in netutils/resolv.  The webclient code has been
               tested on host using gethosbyname(), but still depends on the
               untested resolve logic.
  Status:      Open
  Priority:    Medium, Important but not core NuttX functionality

  Description: Should implement SOCK_RAW, SOCK_PACKET
  Status:      Open
  Priority:    Low

  Description: uIP polling issues / Multiple network interface support:
               (1) Current logic will not support multiple ethernet drivers.
                  Each driver should poll on TCP connections connect on the
                  network supported by the driver; UDP polling should respond
                  with TX data only if the UDP packet is intended for the
                  the network supported by the driver.
               (2) If there were multiple drivers, polling would occur at
                  double the rate.  Fix by using bound IP address in TCP
                  connection (lipaddr) and verifying that it is in the subnet
                  served by the driver.
  Status:      Open
  Priority:    Medium, The feature is not important, but it is important
               for NuttX to resolve the architectural issues.

  Description: Sendoto() and multiple network interface support:
               When polled, would have to assure that the destination IP
               is on the subnet served by the polling driver.
  Status:      Open
  Priority:    Medium, The feature is not important, but it is important
               for NuttX to resolve the architectural issues.

  Description: IPv6 support is incomplete.  Adam Dunkels has recently announced
               IPv6 support for uIP (currently only as part of Contiki).  Those
               changes need to be ported to NuttX.
  Status:      Open
  Priority:    Medium

  Description: Incoming UDP broadcast should only be accepted if listening on
               INADDR_ANY(?)
  Status:      Open
  Priority:    Low

  Description: Read-ahead buffers capture incoming TCP data when no user
               thread is recv-ing the data.  Should add some driver call to
               support throttling; when there is no listener for new data, the
               driver should be throttled.  Perhaps the driver should disable
               RX interrupts when throttled and re-anable on each poll time.
               recvfrom would, of course, have to un-throttle.
  Status:      Open
  Priority:    Medium

  Description: Need to standardize collection of statistics from network
               drivers.  examples/nsh ifconfig command should present
               statistics.
  Status:      Open
  Priority:    Low

  Description: Outgoing packets are dropped and overwritten by ARP packets
               if the destination IP has not been mapped to a MAC.  Could
               improve send() performance by explicitly performing ARP before
               sending the packet.
  Status:      Open
  Priority:    Medium

  Description: Port PPP support from http://contiki.cvs.sourceforge.net/contiki/contiki-2.x/backyard/core/net/ppp/
  Status:      Open
  Priority:    Low

  Description: At present, there cannot be two concurrent active TCP send
               operations in progress using the same socket.  This is because
               the uIP ACK logic will support only one transfer at a time.  The
               solution is simple: A mutex will be needed to make sure that each 
               send that is started is able to be the exclusive sender until all of
               the data to be sent has been ACKed.
  Status:      Open.  There is some temporary logic to examples/nsh that does
               this same fix and that temporary logic should be removed when
               send() is fixed.
  Priority:    Medium-Low.  This is an important issue for applications that
               send on the same TCP socket from multiple threads.

  Description: TCP supports read-ahead buffering to handle the receipt of
               TCP/IP packets when there is no read() in place.  Should such
               capability be useful for UDP?  PRO: Would reduce packet loss
               and enable support for poll()/select().  CON: UDP is inherently
               lossy so why waste memory footprint?
  Status:      Open
  Priority:    Medium

  Description: poll()/select() is not implemented for UDP sockets because they do
               do not support read-ahead buffering.  Therefore, there is never
               a case where you can read from a UDP socket without blocking.
  Status:      Open, depends on UDP read-ahead support
  Priority:    Medium

  Description: sockets do not support all modes except for O_NONBLOCK. Sockets
               support only (1) TCP/IP non-blocking read operations when read-ahead
	       buffering is enabled, and (2) TCP/IP accept() operations when TCP/IP
	       connection backlog is enabled.
  Status:      Open
  Priority:    Low.

  Description: THTTPD is included in the source tree, but has not yet been fully
               integrated.
  Status:      Open
  Priority:    High

o USB (drivers/usbdev)
  ^^^^^^^^^^^^^^^^^^^^

  Description: The USB bulk storage class driver configuration (examples/usbstorage)
               does not work reliably when debug is disabled (CONFIG_DEBUG+CONFIG_DEBUG_VERBOSE
               +CONFIG_DEBUG_USB) on WinXP (Linux appears to be fine).  A race condition would
               would be a possibility.  The symptom is that that WinXP sends a MODE SENSE (6)
               command with an unsupported mode page (0x1c/0x00)
  Status:      Open
  Priority:    High

o Libraries (lib/)
  ^^^^^^^^^^^^^^^^

  Description: sscanf() and lib_vsprintf() do not support floating point
               values.
  Status:      Open
  Priority:    Low

  Description: The definition of environ in stdlib.h is bogus and will not
               work as it should.  This is because the underlying
               representation of the environment is not an arry of pointers.
  Status:      Open
  Priority:    Medium

  Description: fgets implementation does not use C-buffered I/O, but rather
               talks to serial driver directly via read().  It includes VT-100
               specific editting commands.  This gets should be renamed readlin()
               and a more generic fgets() should be implemented.
  Status:      Open
  Priority:    Low (unless you are using mixed C-buffered I/O with fgets and
               fgetc, for example).

  Description: Need some minimal termios support... at a minimum, enough to
               switch between raw and "normal" modes to support behavior like
               that needed for readline().
  Status:      Open
  Priority:    Low

o File system / Generic drivers (fs/, drivers/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Implement chmod(), truncate().
  Status:      Open
  Priority:    Low

  Description: FAT: long file names
  Status:      Open
  Priority:    Medium

  Description: The CAN driver is untested.  Add a test for the CAN driver.
  Status:      Open
  Priority:    Medium

  Description: At present, the CAN driver does not support the poll() method.
  Status:      Open
  Priority:    Low

  Description: There is no way to remove a FIFO or PIPE created in the
               psuedo filesystem.  Once created, they persist indefinitely
               and cannot be unlinked.  This is actually a more generic
               issue:  unlink does not work for anything in the psuedo-
               filesystem.
  Status:      Open, but partially resolved: pipe buffer is at least freed
               when there are not open references to the pipe/FIFO.
  Priority:    Medium

  Description: The ROMFS file system does not verify checksums on either
               volume header on on the individual files.
  Status:      Open
  Priority:    Low.  I have mixed feelings about if NuttX should pay a
               performance penalty for better data integrity.

  Description: The simple SPI based MMCS/SD driver in fs/mmcsd does not
               yet handle multiple block transfers.
  Status:      Open
  Priority:    Medium-Low

  Description: At present, mmap() only works with file descriptors associated
               with a ROMFS file system.  Generalize this logic so that if
               mmap is not supported by the file system or block driver, it
               will allocate memory and copy the file into RAM.  This would
               need some centralized logic so that the memory region would
               be shared on later mmap()'s on the same inode.  Reference counting
               would be required so that the multiply mmap()'ed region persists
               until the last munmap().
  Status:      Open
  Priority:    Low

o Graphics subystem (graphics/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: If CONFIG_NX is enabled, the build fails the first time
               saying that there is "No rule to make target..." for one of the
               auto-generated graphics files.  This is a nuisance, but if you
               simply build again (with the source files already auto-generated)
               the problem does not reoccur.
  Status:      Open
  Priority:    Low, the work-around is simple

  Description: Testing of all APIs is not complete.  See
               http://nuttx.sourceforge.net/NXGraphicsSubsystem.html#testcoverage
  Status:      Open
  Priority:    Medium

o Pascal Add-On (pcode/)
  ^^^^^^^^^^^^^^^^^^^^^^

  Description: Need APIs to verify execution of P-Code from memory buffer.
  Status:      Open
  Priority:    Low

  Description: Loader and object format may be too large for some small
               memory systems.  Consider ways to reduce memory footprint.
  Status:      Open
  Priority:    Medium

o Documentation (Documentation/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Need to document which APIs can be used in interrupt
               handlers (like mq_send and sem_post) and which cannot.
  Status:      Open
  Priority:    Low

o Build system
  ^^^^^^^^^^^^

  Description: Some names under arch are still incorrect.  These should be
               processor architecture names:  pjrc-8051 should be 805x
  Status:      Open
  Priority:    Low

  Description: configs/pjrc-8051 should be configs/pjrc-87c52
  Status:      Open
  Priority:    Low

  Description: Dependencies do not work correctly under configs/<board>/src
               (same as arch/<arch>/src/board).
  Status:      Open
  Priority:    Medium (maybe higher for z80 target)

  Description: It would be nice to de-couple some of the behaviors enabled by
               CONFIG_DEBUG.  For example, CONFIG_DEBUG turns on debug output,
               but also disables optimization make the binary much bigger.
  Status:      Open
  Priority:    Low.  There workaround is easy.. just edit the configuration's
               Make.def file to control the behavior that you want.

  Description: Need a NuttX configuration tool.  The number of configuration
               settings has become quite large and difficult to manage manually.
  Status:      Open
  Priority:    Medium-low

  Description: At present, NuttX builds only under Linux or Cygwin.
               Investigate the possibility of a native Windows build using
               something like the GNUWin32 tools (coreutils+make+grep+sed+uname).
  Status:      Open
  Priority:    Low

o NuttShell (NSH) (examples/nsh)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: When the telnetd front end is received, each TCP packet
               received causes a prompt (nsh >) to be presented.  The
               prompt should only be presented when the user enters a
               carriage return.
  Status:      Open
  Priority:    Low

  Description: The wget command has been incorporated into NSH, however
               it is still untested as of this writing (only because I
               have not had the correct network setup for the testing
               yet).  Since wget depends on the also untest uIP resolv/
               logic, it is like non-functional.
  Status:      Open
  Priority:    Med-High

  Description: Add support to NSH to run NXFLAT programs from a ROMFS file system
  Status:      Open
  Priority:    Low

o Other Applications & Tests (examples/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: The redirection test (part of examples/pipe) terminates
               incorrectly on the Cywgin-based simulation platform (but works
               fine on the Linux-based simulation platform).
  Status:      Open
  Priority:    Low

  Description: examples/wget is untested on the target (it has been tested
               on the host, but not in the target using the uIP resolv logic).
  Status:      Open
  Priority:    Med

  Description: examples/sendmail is untested on the target (it has been tested
               on the host, but not on the target.
  Status:      Open
  Priority:    Med


o Linux/Cywgin simulation (arch/sim)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: The simulated serial driver has some odd behavior.  It
               will stall for a long time on reads when the C stdio buffers are
               being refilled. This only effects the behavior of things like
               fgetc().  Workaround: Set CONFIG_STDIO_BUFFER_SIZE=0, suppressing
               all C buffered I/O.
  Status:      Open
  Priority:    Low (because the simulator is only a test/development platform)

  Description: Simulator does not build correctly on 64-bit machines.  Two
               issues:
               1) It saves addresses in 32-bit types and these fail when cast
                  to pointers on a 64-bit host.
               2) up_setjmp.S does not build
  Status:      Open
  Priority:    Medium and increasing (as 32-bit hosts gradually disappear)

o ARM (arch/arm/)
  ^^^^^^^^^^^^^^^

  Description: ARM interrupt handling performance could be improved in some
               ways. One easy way is to use a pointer to the context save
               area in current_regs instead of using up_copystate so much.
               see handling of 'current_regs" in arch/arm/src/cortexm3/* for
               examples of how this might be done.
                Status:      Open
  Priority:    Low

  Description: The ARM and Cortex-M3 interrupt handlers restores all regisers
               upon return. This could be improved as well:  If there is no
               context switch, then the static registers need not be restored
               because they will not be modified by the called C code.
               (see arch/sh/src/sh1/sh1_vector.S for example)
  Status:      Open
  Priority:    Low

  Description: The Cortex-M3 user context swich logic uses SVCall instructions.
               This user context switching time could be improved by eliminating
               the SVCalls and developing assembly language implementations
               of the context save and restore logic.
  Status:      Open
  Priority:    Low

o ARM/C5471 (arch/arm/src/c5471/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: UART re-configuration is untested and conditionally compiled out.
  Status:      Open
  Priority:    Medium.  ttyS1 is not configured, but not used; ttyS0 is configured
               by the bootloader

o ARM/DM320 (arch/arm/src/dm320/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: config/ntos-dm320: It seems that when a lot of debug statements
               are added, the system no longer boots.  This is suspected to be
               a stack problem: Making the stack bigger or removing arrays on
               the stack seems to fix the problem (might also be the
               bootloader overwriting memory)
  Status:      Open
  Priority:    Medium

  Description: A USB device controller driver was added but has never been tested.
  Status:      Open
  Priority:    Medium

  Description: A framebuffer "driver" was added, however, it remains untested.
  Status:      Open
  Priority:    Medium

  Description: In order to use the framebuffer "driver" additional video encoder
               logic is required to setupt composite video output or to interface
               with an LCD.
  Status:      Open
  Priority:    Medium (high if you need to use the framebuffer driver)

o ARM/i.MX (arch/arm/src/imx/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: The basic port of the i.MX1 architecuture is underway.  The port
               is incomplete (as of this writing, is still lacks a timer, interrupt
               decoding, USB, network) and untested.
  Status:      Open (and in work)
  Priority:    Medium (high if you need i.MX1/L support)

  Description: SPI methods are not thread safe.  Needs a semaphore to protect from re-entrancy.
  Status:      Open
  Priority:    Medium -- Will be very high if you do SPI access from multiple threads.

o ARM/LPC214x (arch/arm/src/lpc214x/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Should use Vector Interrupts
  Status:      Open
  Priority:    Low

  Description: USB DMA not fully implemented. Partial logic is in place but it is
               fragmentary and bogus.
  Status:      Open
  Priority:    Low

  Description: USB Serial Driver reports wrong error when opened before the
               USB is connected (reports EBADF instead of ENOTCONN)
  Status:      Open
  Priority:    Low

  Description: The USB bulk storage class driver configuration (examples/usbstorage)
               does not work reliably when debug is disabled (CONFIG_DEBUG+CONFIG_DEBUG_VERBOSE
               +CONFIG_DEBUG_USB) on WinXP (Linux appears to be fine).  A race condition would
               would be a possibility.  The symptom is that that WinXP sends a MODE SENSE (6)
               command with an unsupported mode page (0x1c/0x00)
  Status:      Open
  Priority:    High

  Description: At present the SPI driver is polled.  Should it be interrupt driven?
               Look at arch/arm/src/imx/imx_spi.c -- that is a good example of an
               interrupt driven SPI driver.  Should be very easy to part that architecture
               to the LPC.
  Status:      Open
  Priority:    Medium

  Description: SPI methods are not thread safe.  Needs a semaphore to protect from re-entrancy.
  Status:      Open
  Priority:    Medium -- Will be very high if you do SPI access from multiple threads.

  Description: At present the SPI driver is polled -AND- there is a rather large, arbitrary,
               delay in one of the block access routines.  The purpose of the delay is to
               avoid a race conditions.  This begs for a re-design -OR- at a minimum, some
               optimiation of the delay time.
  Status:      Open
  Priority:    Medium

  Desription:  I am unable to initialize a 2Gb SanDisk microSD card (in adaptor) on the
               the mcu123 board.  The card fails to accept CMD0.  Doesn't seem like a software
               issue, but if anyone else sees the problem, I'd like to know.
  Status:      Open
  Priority:    Uncertain

o ARM/STR71x (arch/arm/src/str71x/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Verify SPI driver and integrate with MMC support. This effort is stalled
               at the moment because the slot on the Olimex board only accepts MMC card;
               I have no MMC cards, only SD cards which won't fit into the slot.
  Status:      Open
  Priority:    Medium

  Description: Develop a USB driver and integrate with existing USB serial and storage
               class drivers.
  Status:      Open
  Priority:    Medium

  Description: SPI methods are not thread safe.  Needs a semaphore to protect from re-entrancy.
  Status:      Open
  Priority:    Medium -- Will be very high if you do SPI access from multiple threads.

o ARM/LM3S6918 (arch/arm/src/lm3s/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Still need to implement I2C
  Status:      Open
  Priority:    Low

  Description: Should terminate SSI/SPI transfer if an Rx FIFO overrun occurs.
               Right now, if an Rx FIFO overrun occurs, the SSI driver hangs.
  Status:      Open
  Priority:    Medium, If the transfer is properly tuned, then there should not
               be any Rx FIFO overruns.

  Description: Dependency generation is currently disabled when a Windows native
               toolchain is used.  I think that the only issue is that all of the
               Windows dependencies needed to be quoted in the Make.dep files.
  Status:      Open
  Priority:    Low -- unless some dependency-related build issues is discovered.

o pjrc-8052 / MCS51 (arch/pjrc-8051/)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Current status:
               - Basic OS task management seems OK
               - Fails when interrupts enabled.  The stack pointer is around
                 0x6e before the failure occurs.  It looks like some issue
                 when the stack pointer moves from the directly to indirectly
                 addressable region (0x80 boundary).
               - Work on the 8052 is temporarily on hold
  Status:      Open
  Priority:    Low, 8051 is a tough platform because of the tiny stack.

  Description: Use timer 0 as system timer.  Timer 2 is needed for second UART.
               Logic is implemented, but there needs to be a system
               configuration to change the ticks-per-second value to match the
               timer interrupt rate
  Status:      Open
  Priority:    Low

  Description: During build, there are several integer overflows reported:
               sched/gmtime_r.c aroud lines 184 and 185
               sched/clock_initialize.c at line 107
               sched/pthread_create.c at 330
               examples/ostest/barrier.c around lines 53 and 74
               examples/ostest/sighand.c at 225 and 244
               driver/serial.c in usleep calls around 347 and 354
  Status:      Open
  Priority:    Medium

  Description  Global data is not being initialized.  Logic like that of SDCCs
               crt0*.s needs to be incorporated into the system boot logic
  Status:      Open
  Priority:    Low -- only because there as so many other issues with 8051


o Hitachi/Renesas SH-1 (arch/sh/src/sh1)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description:  There are instabilities that make the SH-1 port un-usable.  The
                nature of these is not understood; the behavior is that certain SH-1
                instructions stop working as advertised.  I have seen the following
                examples:

                  412b jmp @r1 - Set a return address in PR, i.e., it behaved like
                       410b jsr @r1.  Normally 412b works correctly, but in the failure
                       condition, it reliably set the PR.
                  69F6 mov.l @r15+,r9 - wrote the value of R1 to @r15+.  This behavior
                       does not correspond to any known SH-1 instruction

                This could be a silicon problem, some pipeline issue that is not
                handled properly by the gcc 3.4.5 toolchain (which has very limit
                SH-1 support to begin with), or perhaps with the CMON debugger.  At
                any rate, I have exhausted all of the energy that I am willing to put
                into this cool old processor for the time being.
  Status:       Open
  Priority:     Low -- because the SH-1, SH7032, is very old and only of historical
                interest.

  Description:  arch/sh has been restructured to support M16C.  Need to verify that
                SH-1 still builds.
  Status:       Open
  Priority:     Low

  Description:  The M16C target cannot be built.  The GNU m16c-elf-ld link fails with 
                the following message:

                m32c-elf-ld: BFD (GNU Binutils) 2.19 assertion fail /home/Owner/projects/nuttx/buildroot/toolchain_build_m32c/binutils-2.19/bfd/elf32-m32c.c:482

                Where the reference line is:

                /* If the symbol is out of range for a 16-bit address,
                   we must have allocated a plt entry.  */
                BFD_ASSERT (*plt_offset != (bfd_vma) -1);

                No workaround is known at this time.
  Status:       Open
  Priority:     High -- this is a show stopper for M16C.

o Renesas M16C/26 (arch/sh/src/m16c)
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  Description: Coding of the initial port is complete, but is untested.
  Status:      Open
  Priority:    Low

  Description: Serial drivers were developed for the M16C, however, the SKP16C26
               StarterKit has no serial connectors.
  Status:      Open
  Priority:    Low

  Description: Should implement SPI, I2C, Virual EEPROM, FLASH, RTC drivers
  Status:      Open
  Priority:    Medium

o z80/z8/ez80 (arch/z80)
 ^^^^^^^^^^^^^^^^^^^^^^^

  Description: The SDCC version the same problems with interger overflow during
               compilation as described for pjrc-8051.  At typical cause is code like
               usleep(500*1000) which exceeds the range of a 16-bit integer
  Status:      See pjrc-8051
  Priority:    See pjrc-8051

  Description: The simulated Z80 serial console (configs/z80sim/src/z80_serial.c +
               driver/serial.c) does not work.  This is because there are
               no interrupts in the simulation so there is never any serial
               traffic.
  Status:      Open
  Priority:    Low -- the simulated console is not critical path and the designs
               to solve the problem are complex.

  Description: ZDS-II Librarian complains that the source for the .obj file
               is not in the library.
  Status:      Open
  Priority:    Low, thought to be cosmetic.  I think this is a consequence of
               replacing vs. inserting the library.

  Description: The ZDS-II compiler (version 4.10.1) fails with an internal error
               while compiler mm/mm_initialize.  This has been reported as
               incident 81509.

               I have found the following workaround that I use to build for the
               time being:

               --- mm/mm_initialize.c.SAVE	2008-02-13 08:06:46.833857700 -0600
               +++ mm/mm_initialize.c	2008-02-13 08:07:26.367608900 -0600
               @@ -94,8 +94,11 @@
               {
                  int i;

               +#if 0 /* DO NOT CHECK IN */
                  CHECK_ALLOCNODE_SIZE;
                  CHECK_FREENODE_SIZE;
               +#endif

               /* Set up global variables */

  Status:      Open
  Priority:    High

  Description: Add support for prioritized ez8 interrupts.  Currently logic supports
               only nominal interrupt priority.
  Status:      Open
  Priority:    Low

  Description: The z8Encore! port has only been verified on the ZDS-II instruction
               set simulator.
  Status:      Open
  Priority:    Medium

  Description: Upgrade to the ZDS-II Z8Encore! 4.11.0 toolchain
  Status:      Open
  Priority:    Low

  Description: The XTRS target (configs/xtrs) has a clean problem. The clean
               rule removes .asm files.  This works because there are no .asm
               files except in sub-directories that are provided from 'make clean' --
               except for XTRS:  It has a .asm file in its src/ directory that
               gets removed everytime clean is performd.
  Status:      Open
  Priority:    High if you happen to be working with XTRS.

  Description: A "generic" SPI and I2C drivers have been coded for the eZ80Acclaim!
               However, these remains untested since I have no SPI or I2C devices for
               the board (yet).
  Status:      Open
  Priority:    Med

  Description: SPI methods are not thread safe.  Needs a semaphore to protect from re-entrancy.
  Status:      Open
  Priority:    Medium -- Will be very high if you do SPI access from multiple threads.

  Description: A "generic" I2C driver has been coded for the eZ8Encore!
               However, this remains untested since I have no I2C devices for
               the board (yet).
  Status:      Open
  Priority:    Med

o z16 (arch/z16)
^^^^^^^^^^^^^^^^

  Description: ZDS-II Librarian complains that the source for the .obj file
               is not in the library.
  Status:      Open
  Priority:    Low, thought to be cosmetic.  I think this is a consequence of
               replacing vs. inserting the library.

  Description: When the interrupt-driven serial driver is used, the system
               hangs.  This is because of TX ready (TRDE) interrupts that
               get lost while interrupts are disabled.  The existing
               serial driver appears to be limited to hardware with a
               latching, level-sensitive TX ready interrupt.
  Status:      Open
  Priority:    Medium. A polled, write-only serial driver is used in the
               interim for system testing.

  Description: The system delays do not appear to be correct with the
               examples/ostest/timedmqueue.c test.
  Status:      Open
  Priority:    Medium-High

  Description: At present, the z16f port does not run properly when CONFIG_DEBUG
               is disabled:  The obvious symptom is that there is no printf()
               output.  I have isolated with problem to errors in optimization.
               With -reduceopt on the command line, I can get the printf output.
               However, there are still errors in the compiled code -- specifically
               in sched/timer_create.c.

               I have submitted a bug report to ZiLOG for this (support incident
               81400).  You can see the status of the bug report (and lots more
               technical detail) here:
               http://support.zilog.com/support/incident/incident_support.asp?iIncidentId=81400&iSiteId=1&chLanguageCode=ENG

               Summary of ZiLOG analysis: "This is a ZNEO compiler problem. ... [a] workaround
               is to replace:
                   if ( !timerid || (clockid != 0) )
                By:
                   if ((clockid != 0) || !timerid)"

  Status:      Open
  Priority:    Medium-High

  Description: The pascal add-on does not work with the z16f (that is
               configuration z16f2800100zcog/pashello).  This appears to be
               another ZDS-II error:  when executing the instruction
               SYSIO 0, WRITESTR a large case statement is executed.  This
               involves a call into the ZiLOG runtime library to __uwcase().
               __uwcase is passed a pointer to a structure containing jump
               information.  The cause of the failure appears to be that
               the referenced switch data is bad.
               This is submited as ZiLOG support incident 81459.

               Summary of ZiLOG analysis: "This is a ZNEO run time library problem.
               One workaround is to replace the line 58 in uwcase.asm

               From:
                      ADD       R9,#4             ; Skip handler
               To:
                      ADD       R9,#2             ; Skip handler

               And add uwcase.asm to the project.

               If the customer does not want to modify uwcase.asm then the other
               workaround is to add a dummy case and make it same as default:

               case 0x8000:
               default:

               This will make sure that uwcase is not called but ulcase is called."
  Status:      Open.  Due to licensing issues, I cannot include the modified
               uwcase in the NuttX code base.
  Priority:    Medium

  Description: Add support to maintain SPOV in context switching.  This
               improvement will provide protection against stack overflow
               and make a safer system solution.
  Status:      Open
  Priority:    Low

  Description: Add support for prioritized interrupts.  Currently logic supports
               only nominal interrupt priority.
  Status:      Open
  Priority:    Low

  Description: Upgrade to the ZDS-II ZNEO 4.11.1 toolchain
  Status:      Open
  Priority:    Low