STM32 USB support

[Chris Holgate <chris at zynaptic dot com>]

Simon Kallweit wrote:
> Chris Holgate schrieb:
>>
>> It's stable in my application using my own Linux kernel driver (several
>> million bulk and interrupt transactions and counting!).
>>   
> That sound's pretty stable to me :)

OK - I've now done a bit of tidying up which I hope won't have broken
it!  The latest version of the package is here:

http://www.zynaptic.com/ecos/packages/stm32-usb-20090519.epk

There are a couple of minor TODO's which I need to revisit before a
proper release, but nothing significant.

>> However, I've not had much luck getting it working with the standard
>> eCos test framework - although I now suspect thats a Linux usbfs issue
>> rather than my driver.  I also need to sort out some proper
>> documentation!
> 
> Well, I could do some testing too and see where I get.

That would be very helpful, although I think that the standard host-side
tests have only ever been run on a pretty old version of Linux.  I'd
have more confidence in testing against some standard drivers like a
virtual serial port or a 'memory stick' device.

>> There is a significant difference from the other USB drivers which I
>> should probably flag up (and document).  The endpoint configuration is
>> generated dynamically from the USB descriptors.  This gives a lot of
>> flexibility and potentially allows support for multiple configurations
>> (untested!).  However, the downside is that I had to leave out devtab
>> support since the devtab entries need to be set statically.
>>   
> Don't you think it's possible to have both options? I haven't looked at
> the USB subsystem or any drivers, but I think a public driver should
> behave as the subsystem intends. Maybe the subsystem could be extended
> for more dynamic usage though.

The official docs say "To support this the device driver can provide a
devtab entry for each endpoint".  I took that to mean that devtab
support was optional - and the dynamic endpoint configuration is a much
more useful feature IMHO.

Previously supported hardware has had fixed endpoint configurations
which makes the static devtab entries easy to implement.  However, with
dynamic endpoint configuration, the low-level driver doesn't know
a-priori what endpoints to generate devtab entries for - and nor should it!

Copied to the list, since I'm sure there are other people who would like
to comment...

Chris.