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

[Samuel Thibault]

Hello,

Samuel Thibault, on dim. 26 févr. 2017 03:48:32 +0100, wrote:
> Samuel Thibault, on dim. 26 févr. 2017 02:50:05 +0100, wrote:
> > Please note in your todo for the input part, that ttyio will have to
> > call read_buff_add for each received character, when that method is
> > not NULL (that's actually the only driver using it, so we will really
> > need a tester for this exact driver).
> 
> More precisely, it's the spk_ttyio_ldisc_ops->receive_buf2 method which
> should call read_buff_add for each received character.
> 
> 
> The step further will be implementing spk_ttyio_in and
> spk_ttyio_in_nowait.  I believe the easiest way is the following:

I forgot the part that stops the tty layer from sending characters:

> - define an spk_ldisc_data structure containing just one character (buf),
> and a semaphore.

and one int (buf_free).

> - on ldisc_open, allocate a pointer to such structure, set
> tty->disc_data to point to it, and initialized the semaphore to 0
> tokens.

and initialize buf_free to 1.

> - 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).

Here, *just before* storing the character in buf, check buf_free: if
it is 0, return 0. otherwise, call mb(), and continue with what I wrote
above.

> - in spk_serial_in, call down_timeout(usecs_to_jiffies(SPK_SERIAL_TIMEOUT)),
>   - on success, copy the character stored in buf, then call tty_schedule_flip() and return the copy
>   - on failure (timed out), return 0xff.
> 
> - in spk_serial_in_nowait, call down_trylock(),
>   - on success, copy the character stored in buf, then call tty_schedule_flip() and return the copy
>   - on failure, return 0.

In each case, right after the copy, call mb() and set buf_free to 1.


Actually, these two function could be factorized to just one, which
takes a long timeout parameter (in jiffies) and returns an int
instead of a char, and uses down_trylock when the timeout is 0 and
down_timeout otherwise, and returns -1 instead of 0 on failure. And then
make spk_serial_in use it and return 0xff when getting -1, and make
spk_serial_in_nowait return 0 when getting -1. Cleaning that returned
value convention can be another patch later.

Samuel