Commit 87ef7779 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Jaroslav Kysela
Browse files

[ALSA] seq-timer: restrict timer frequencies 



Modules: ALSA sequencer

When no default timer frequency has been set, initialize_timer() just
uses the maximum frequency supported by the timer, which is ridiculously
high on 96 kHz timers.

This patch introduces a default frequency of 1000 Hz for this case, and
makes sure that a frequency set by the user isn't too high.

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
parent 051b5165

sound/core/seq/seq_timer.c

+17 −3
Original line number Diff line number Diff line
@@ -34,6 +34,11 @@ extern int seq_default_timer_device; 
extern int seq_default_timer_subdevice;

extern int seq_default_timer_resolution;



/* allowed sequencer timer frequencies, in Hz */

#define MIN_FREQUENCY		10

#define MAX_FREQUENCY		6250

#define DEFAULT_FREQUENCY	1000



#define SKEW_BASE	0x10000	/* 16bit shift */



static void snd_seq_timer_set_tick_resolution(seq_timer_tick_t *tick,
@@ -325,17 +330,26 @@ int snd_seq_timer_stop(seq_timer_t * tmr) 
static int initialize_timer(seq_timer_t *tmr)

{

	snd_timer_t *t;

	unsigned long freq;



	t = tmr->timeri->timer;

	snd_assert(t, return -EINVAL);



	freq = tmr->preferred_resolution;

	if (!freq)

		freq = DEFAULT_FREQUENCY;

	else if (freq < MIN_FREQUENCY)

		freq = MIN_FREQUENCY;

	else if (freq > MAX_FREQUENCY)

		freq = MAX_FREQUENCY;



	tmr->ticks = 1;

	if (tmr->preferred_resolution &&

	    ! (t->hw.flags & SNDRV_TIMER_HW_SLAVE)) {

	if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE)) {

		unsigned long r = t->hw.resolution;

		if (! r && t->hw.c_resolution)

			r = t->hw.c_resolution(t);

		if (r) {

			tmr->ticks = (unsigned int)(1000000000uL / (r * tmr->preferred_resolution));

			tmr->ticks = (unsigned int)(1000000000uL / (r * freq));

			if (! tmr->ticks)

				tmr->ticks = 1;

		}

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