Issues when adding a multi-port PCI serial card

[Peter Dufault]

I've added an 8-port RS232 PCI Mezzanine Card to the "beatnik" BSP.  The console (aka serial port) code is confusing.

I decided I should use what is in "bsp/console-termios.h"  as opposed to the "legacy console" approach, *even though* "legacy console" is used in many recent BSPS.

* Is that correct?

That approach went well, I created a replacement shared PowerPC console in "bsps/powerpc/shared/console/console-config.c" with only 129 lines of code and half of it comments.

Where does the driver go:  Next I had to add the PCI multi-port serial card driver.  I put it in "bsps/shared/dev/pci/mp_serial.c".  The other directory choice was "bsps/shared/dev/serial".  I didn't like either, the "dev/pci" is very associated with PCI discovery and the "dev/serial" is very associated with the generic low-level serial driver support, even thought it has the "legacy-console" cruft in it.

* Where should it go?

Difficulty in assigning common TTY names: Since my new shared PowerPC "console-config.c" created "/dev/ttyS0" and "/dev/ttyS1" I wanted to name the new serial devices with a number that started at 2, i.e., "/dev/ttyS2".

* Is there a way in the "console-termios" framework to know what the highest "minor number" for a serial port is?  I searched, gave up, and made it a configuration item.

Next I had to figure out the best way to probe and discover the board.

* I wanted to add an RTEMS_SYSINIT_ITEM that would call a probe routine to discover the multiport cards at the appropriate time, after "/dev/console" was discovered but before I wanted to spawn my shell.  I had trouble figuring out what level and order I should use for the probe routine.  I never got this working, my probe routine kept getting called much later then I expected it to.  I need a pointer to the documentation to RTEMS_SYSINIT_ITEM ordering.

Finally, after initial successful loop-back testing, I tried to start an RTEMS shell on one of the new ports.

*Here I'm trying hard to avoid all-caps because this took the most time of all (it should have been easiest), and I gave up!*

* HOW (sorry) do you spawn a shell on a serial port?  The documentation, at https://docs.rtems.org/branches/master/shell/configuration_and_init.html that suggests just setting the shell device name to "/dev/console", or in my case "/dev/ttyS9", is incorrect.  The shell startup is intent on using "stdin" and "stdout".
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Peter
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Peter Dufault
HD Associates, Inc.      Software and System Engineering

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