speakup: Fix 8bit characters from direct synth

When userland echoes 8bit characters to /dev/synth with e.g.

echo -e '\xe9' > /dev/synth

synth_write would get characters beyond 0x7f, and thus negative when
char is signed. When given to synth_buffer_add which takes a u16, this
would sign-extend and produce a U+ffxy character rather than U+xy.
Users thus get garbled text instead of accents in their output.

Let's fix this by making sure that we read unsigned characters.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Fixes: 89fc2ae80bb1 ("speakup: extend synth buffer to 16bit unicode characters")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240204155736.2oh4ot7tiaa2wpbh@begin
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

speakup: Allow lower values for the flush parameter

Users needing it with the dectlk synth report that a 100ms flush delay
is still noticeable and prefer to set it to e.g. 10ms. This leaves the
default to 4000ms (since hitting it is a sign that the cable is faulty
and should be replaced), but allows to set it as short as 10ms.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20220205232957.bc6o6yyt5hitg754@begin
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

speakup: Make dectlk flush timeout configurable

In case the serial port or cable got faulty, we may not be getting
acknowledgements any more. The driver then currently waits for 4s to
avoid jamming the device. This makes this delay configurable.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20210128180116.1848120-3-samuel.thibault@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

speakup: add the missing synth parameter to all io functions

So that we can avoid the spk_ttyio_synth global variable in the next
commit.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20210126222147.3848175-2-samuel.thibault@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

speakup: Fix wait_for_xmitr for ttyio case

This was missed while introducing the tty-based serial access.

The only remaining use of wait_for_xmitr with tty-based access is in
spk_synth_is_alive_restart to check whether the synth can be restarted.
With tty-based this is up to the tty layer to cope with the buffering
etc. so we can just say yes.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20200804160637.x3iycau5izywbgzl@function
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging/speakup: Move out of staging

The nasty TODO items are done.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20200729003531.907370-1-samuel.thibault@ens-lyon.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>