Hi Joey,

On Tue, Aug 30, 2011 at 05:59:49PM -0400, Joey Oravec wrote:

Dmitry -

In serio_raw.c function serio_raw_write() there's a check:

if (count > 32)
   count = 32;

which coerces any call to write a maximum of 32 bytes. Do you know
why this limitation is in the code? Characters get written
one-by-one to the tty layer so I don't understand why it's there.

The driver was trying to mimic behavior of 2.4 psaux device as close as
possible so 32 bytes limit came from there. Besides I think it is a good
idea to not allow one process hog serio port for too long...

I'm not sure which section of the manpage defines write for a serial
port. In the ordinary case I expected this function to keep
transmitting until complete or an error occurs. If O_NONBLOCK was
specified then I might expect EAGAIN. Right now my calling code
doesn't expect a successful partial write. Do you think this module
is doing the right thing? Can you comment on what the caller must
expect?

I think you should handle partial writes. Even if driver honored
O_NONBLOCK you could get a partial write and not necessarily EAGAIN.

May I ask you what you are using serio_raw for?

Thanks.

-- 
Dmitry