[patch 6/6] staging: speakup: Migrate acntsa, bns, dectlk and txprt to ttyio

[Samuel Thibault]

Hello,

Okash Khawaja, on mar. 28 mars 2017 15:35:08 +0100, wrote:
> On Sun, Feb 26, 2017 at 2:48 AM, Samuel Thibault
> <samuel.thibault at ens-lyon.org> wrote:
> > - in the receive_buf2 method,
> >   - if read_buff_add is defined, just call it for each character and be
> >   done
> >   - otherwise, store the first received character in
> >     ((struct spk_ldisc_data *)tty->disc_data)->buf
> >     , call up() on the semaphore, and return 1 (to tell that you ate the
> >     character).
> 
> 
> I don't fully understand how the return value of receive_buf2 is used
> in flow control. According to Documentation/serial/tty.txt it is the
> number of bytes processed by it, whereas comments on top of
> tty_ldisc_receive_buf function's definition - which returns value
> returned by receive_buf2 - say it is the number of bytes not
> processed.

I believe the comment is wrong: for instance n_tty_receive_buf_common
clearly returns the number of processed bytes, and users (such as
paste_selection, receive_buf from flush_to_ldisc) use it that way.  You
can probably submit a patch that fixes the comment already.

> Also, is the call to tty_schedule_flip in spk_serial_in because we
> returned 1 receive_buf2 so we have to manually tell it to flip buffer?

(note: I meant spk_ttyio_in, of course)

It's because we only returned 1, yes, i.e. we only ate 1 character,
while there probably were more to read, but we didn't eat them, so we
have to tell the tty layer when we are ready to eat more.

Samuel