[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 9c87d9f8ba9fb25cf8aa1782ee2534ef3043c203..65b64a7c456dbd02636e091ca7f8e2498116fa02 100644 (file)
--- a/sound/core/seq/seq_timer.c
+++ b/sound/core/seq/seq_timer.c
@@ -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;
                }