[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: Clemens Ladisch <clemens@ladisch.de>
diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c
index 9c87d9f..65b64a7 100644
--- a/sound/core/seq/seq_timer.c
+++ b/sound/core/seq/seq_timer.c
@@ -34,6 +34,11 @@
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 @@
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;
}
