staging: speakup: flush tty buffers and ensure hardware flow control

[Samuel Thibault]

Okash Khawaja, on dim. 07 mai 2017 19:48:03 +0100, wrote:
> This patch fixes the issue where TTY-migrated synths would take a while to shut up after hitting numpad enter key. When calling synth_flush, even though XOFF character is sent as high priority, data buffered in TTY layer is still sent to the synth. This patch flushes that buffered data when synth_flush is called.
> 
> It also tries to ensure that hardware flow control is enabled, by setting CRTSCTS using tty's termios.
> 
> Reported-by: John Covici <covici at ccs.covici.com>
> Signed-off-by: Okash Khawaja <okash.khawaja at gmail.com>

Reviewed-by: Samuel Thibault <samuel.thibault at ens-lyon.org>

> Index: linux-staging/drivers/staging/speakup/serialio.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/serialio.c
> +++ linux-staging/drivers/staging/speakup/serialio.c
> @@ -30,6 +30,7 @@
>  static void spk_serial_tiocmset(unsigned int set, unsigned int clear);
>  static unsigned char spk_serial_in(void);
>  static unsigned char spk_serial_in_nowait(void);
> +static void spk_serial_flush_buffer(void);
>  
>  struct spk_io_ops spk_serial_io_ops = {
>  	.synth_out = spk_serial_out,
> @@ -37,6 +38,7 @@
>  	.tiocmset = spk_serial_tiocmset,
>  	.synth_in = spk_serial_in,
>  	.synth_in_nowait = spk_serial_in_nowait,
> +	.flush_buffer = spk_serial_flush_buffer,
>  };
>  EXPORT_SYMBOL_GPL(spk_serial_io_ops);
>  
> @@ -268,6 +270,11 @@
>  	return inb_p(speakup_info.port_tts + UART_RX);
>  }
>  
> +static void spk_serial_flush_buffer(void)
> +{
> +	/* TODO: flush the UART 16550 buffer */
> +}
> +
>  static int spk_serial_out(struct spk_synth *in_synth, const char ch)
>  {
>  	if (in_synth->alive && spk_wait_for_xmitr(in_synth)) {
> Index: linux-staging/drivers/staging/speakup/spk_ttyio.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/spk_ttyio.c
> +++ linux-staging/drivers/staging/speakup/spk_ttyio.c
> @@ -85,6 +85,7 @@
>  static void spk_ttyio_tiocmset(unsigned int set, unsigned int clear);
>  static unsigned char spk_ttyio_in(void);
>  static unsigned char spk_ttyio_in_nowait(void);
> +static void spk_ttyio_flush_buffer(void);
>  
>  struct spk_io_ops spk_ttyio_ops = {
>  	.synth_out = spk_ttyio_out,
> @@ -92,6 +93,7 @@
>  	.tiocmset = spk_ttyio_tiocmset,
>  	.synth_in = spk_ttyio_in,
>  	.synth_in_nowait = spk_ttyio_in_nowait,
> +	.flush_buffer = spk_ttyio_flush_buffer,
>  };
>  EXPORT_SYMBOL_GPL(spk_ttyio_ops);
>  
> @@ -99,6 +101,7 @@
>  {
>  	int ret = 0;
>  	struct tty_struct *tty;
> +	struct ktermios tmp_termios;
>  
>  	ret = tty_register_ldisc(N_SPEAKUP, &spk_ttyio_ldisc_ops);
>  	if (ret) {
> @@ -127,6 +130,18 @@
>  	}
>  
>  	clear_bit(TTY_HUPPED, &tty->flags);
> +	/* ensure hardware flow control is enabled */
> +	down_read(&tty->termios_rwsem);
> +	tmp_termios = tty->termios;
> +	up_read(&tty->termios_rwsem);
> +
> +	if (!(tmp_termios.c_cflag & CRTSCTS)) {
> +		tmp_termios.c_cflag |= CRTSCTS;
> +		ret = tty_set_termios(tty, &tmp_termios);
> +		if (ret)
> +			pr_warn("speakup: Failed to set hardware flow control\n");
> +	}
> +
>  	tty_unlock(tty);
>  
>  	ret = tty_set_ldisc(tty, N_SPEAKUP);
> @@ -201,6 +216,11 @@
>  	return (rv == 0xff) ? 0 : rv;
>  }
>  
> +static void spk_ttyio_flush_buffer(void)
> +{
> +	speakup_tty->ops->flush_buffer(speakup_tty);
> +}
> +
>  int spk_ttyio_synth_probe(struct spk_synth *synth)
>  {
>  	int rv = spk_ttyio_initialise_ldisc(synth->ser);
> Index: linux-staging/drivers/staging/speakup/spk_types.h
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/spk_types.h
> +++ linux-staging/drivers/staging/speakup/spk_types.h
> @@ -154,6 +154,7 @@
>  	void (*tiocmset)(unsigned int set, unsigned int clear);
>  	unsigned char (*synth_in)(void);
>  	unsigned char (*synth_in_nowait)(void);
> +	void (*flush_buffer)(void);
>  };
>  
>  struct spk_synth {
> Index: linux-staging/drivers/staging/speakup/speakup_audptr.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/speakup_audptr.c
> +++ linux-staging/drivers/staging/speakup/speakup_audptr.c
> @@ -127,6 +127,7 @@
>  
>  static void synth_flush(struct spk_synth *synth)
>  {
> +	synth->io_ops->flush_buffer();
>  	synth->io_ops->send_xchar(SYNTH_CLEAR);
>  	synth->io_ops->synth_out(synth, PROCSPEECH);
>  }
> Index: linux-staging/drivers/staging/speakup/speakup_decext.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/speakup_decext.c
> +++ linux-staging/drivers/staging/speakup/speakup_decext.c
> @@ -221,6 +221,7 @@
>  static void synth_flush(struct spk_synth *synth)
>  {
>  	in_escape = 0;
> +	synth->io_ops->flush_buffer();
>  	synth->synth_immediate(synth, "\033P;10z\033\\");
>  }
>  
> Index: linux-staging/drivers/staging/speakup/speakup_dectlk.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/speakup_dectlk.c
> +++ linux-staging/drivers/staging/speakup/speakup_dectlk.c
> @@ -293,6 +293,7 @@
>  		synth->io_ops->synth_out(synth, ']');
>  	in_escape = 0;
>  	is_flushing = 1;
> +	synth->io_ops->flush_buffer();
>  	synth->io_ops->synth_out(synth, SYNTH_CLEAR);
>  }
>  
> Index: linux-staging/drivers/staging/speakup/speakup_spkout.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/speakup_spkout.c
> +++ linux-staging/drivers/staging/speakup/speakup_spkout.c
> @@ -125,6 +125,7 @@
>  
>  static void synth_flush(struct spk_synth *synth)
>  {
> +	synth->io_ops->flush_buffer();
>  	synth->io_ops->send_xchar(SYNTH_CLEAR);
>  }
>  
> Index: linux-staging/drivers/staging/speakup/synth.c
> ===================================================================
> --- linux-staging.orig/drivers/staging/speakup/synth.c
> +++ linux-staging/drivers/staging/speakup/synth.c
> @@ -120,6 +120,7 @@
>  
>  void spk_synth_flush(struct spk_synth *synth)
>  {
> +	synth->io_ops->flush_buffer();
>  	synth->io_ops->synth_out(synth, synth->clear);
>  }
>  EXPORT_SYMBOL_GPL(spk_synth_flush);
> 

-- 
Samuel
<d> bah à défaut de ligne TGV, ils ont un GR
 -+- #ens-mim - comment ça, paumé ?! -+-