On Wed, Nov 27, 2002 at 08:45:11PM +0100, Jurij Smakov wrote:
> Hi!
> 
> Recently I have purchased an infamous MA-620 USB infrared adapter (based
> on pl2303 usb-to-serial converter). After a few failed attempts to make it
> work I have discovered a rather lengthy thread on this list, discussing
> the issue preventing the pl2303 driver to operate properly for that device.
> After reading this thread (which looked like a flame at times :-) I still
> do not have a clear understanding of what needs to be done to fix it. So
> maybe someone knowledgeable people would not mind answering some questions
> and/or directing me to the appropriate resources, so that I can try doing
> it. The questions are:

Have you tried the latest 2.5 kernel?  A number of irda changes have
gone into there that might help out with these problems.

> 1. Is it possible to fix the issue (pl2303_set_termios being called in
> the interrupt context, while it obviously was not designed for that) by
> just making the sending of the USB control messages asynchronous
> (usb_submit_urb with callback). Is there any major issue, which I don't
> see due to the lack of experience, which might prevent this approach from
> working (synchronization of USB control messages for speed changes with
> the data stream comes to mind)?

I don't know how this could be fixed.  Any ideas?

> 2. Are 4-5 calls to usb_control_msg really essential for the change of the
> parameters? It seems like the alternative driver (from Prolific site) can
> do it by just _one_ control message, if it is not some special case, like
> transition to/from zero baud speed.

I don't know if it is essential or not, due to the lack of
documentation.

> 3. Where can I find documentation regarding the data/commands passed in
> the control messages sent by pl2303_set_termios? Obvious sources
> (linux/Documentation, Prolific website, comments in the source) didn't
> reveal much.

I don't know.  The original driver was written by someone who reverse
engineered the protocol.

thanks,

greg k-h


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