[ECOS] serial driver questions

[Grant Edwards <grante at visi dot com>]

Hello eCosians,

  I'm setting up an eCos system on custom hardware to support
  an application that is being ported from a previous design,
  and I've some questions about the serial driver:


Non-Blocking I/O
----------------

  In order to avoid re-designing the application completely, I
  need to provide non-blocking serial I/O.

  Additionally, one of the requirements for the application is
  that it be able to find out how much space is available in
  the tx buffer [there's a lot of existing stuff that depends
  on this ability, and not having it would require ton's of
  application code to be scrapped.]

  I will probably add cyg_io_get_config keys that let the
  application find out how much data is waiting to be read
  and/or how much space is available in the transmit buffer.
  The application could then make sure that it makes read/write
  calls that are not going to block.

  I could also add a non-blocking mode to the serial driver so
  that read/write calls would return immediately after
  performing as much of the read or write operation was
  possible without blocking.

  I rather like the idea of a non-blocking mode, but since I
  have to do the first option anyway, it's not really needed.


Serial-Port Configuration
-------------------------

  I need more configuration information for my UART than is
  provided in the standard cyg_serial_info_t type. For example,
  I need to configure Xon/Xoff characters for send and receive
  as well as other flow-control and hardware configuration
  stuff.  I'll also need an additional baud rate of 460800.

  BTW, there's a typo in serialio.h: it should be
  CYGNUM_SERIAL_BAUD_230400 rather than
  CYGNUM_SERIAL_BAUD_234000

  Is there a compatible way to extend the cyg_serial_info_t
  structure to provide additional data to my serial hardware
  interface module without breaking my module's compatibility
  with the standard eCos serial driver?

  I think it would be sufficient if I could just add stuff on
  to the end of the structure that is passed to the
  set_config/CYG_IO_SET_CONFIG_SERIAL_INFO) and expect the
  serial driver to pass the data along to the interface module
  and preserve the data so that it is returned by the
  get_config/CYG_IO_GET_CONFIG_SERIAL_INFO call.
  
  Alternatively, is there a way to add a get/set_config key
  that is just passed through the serial driver to the hardware
  interface module?  This would require two additional entries in
  the SERIAL_FUNS table -- one for get and one for set.
  

Modem Status/Control Lines
--------------------------

  I don't see any way to either read or set any of the modem
  control/status lines (RTS,CD,RI,DSR,DTR).  My application
  requires control of these lines, so I'll have to add
  something to handle this also.


The net result is that I have to add these features.

I'd like to do it in a way that is generally useful and can be
merged into the standard distribution.  [For the moment, we'll
assume this is due to my desire to contribute to the greater
good of society and it's not just me trying to offload
maintenance responsibilities and avoid the headache of
maintaining a set of code that parallels the standard eCos
driver.]

Suggestions?

-- 
Grant Edwards
grante@visi.com