ALSA: pcm_native - fix runtime->boundary calculation
The code in pcm_lib updating runtime->hw_ptr_interrupt expects
that runtime->boundary is divisible with runtime->period_size.
Thanks are going to Clemens Ladisch for the notice.
Fix the runtime->boundary calculation using buffer_size * period_size
as base and find a least common multiple for 32bit platforms when
the expression might overflow.
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 7a002db..9cbaf90 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -27,6 +27,7 @@
#include <linux/pm_qos_params.h>
#include <linux/uio.h>
#include <linux/dma-mapping.h>
+#include <linux/math64.h>
#include <sound/core.h>
#include <sound/control.h>
#include <sound/info.h>
@@ -366,6 +367,38 @@
return usecs;
}
+static int calc_boundary(struct snd_pcm_runtime *runtime)
+{
+ u_int64_t boundary;
+
+ boundary = (u_int64_t)runtime->buffer_size *
+ (u_int64_t)runtime->period_size;
+#if BITS_PER_LONG < 64
+ /* try to find lowest common multiple for buffer and period */
+ if (boundary > LONG_MAX - runtime->buffer_size) {
+ u_int32_t remainder = -1;
+ u_int32_t divident = runtime->buffer_size;
+ u_int32_t divisor = runtime->period_size;
+ while (remainder) {
+ remainder = divident % divisor;
+ if (remainder) {
+ divident = divisor;
+ divisor = remainder;
+ }
+ }
+ boundary = div_u64(boundary, divisor);
+ if (boundary > LONG_MAX - runtime->buffer_size)
+ return -ERANGE;
+ }
+#endif
+ if (boundary == 0)
+ return -ERANGE;
+ runtime->boundary = boundary;
+ while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)
+ runtime->boundary *= 2;
+ return 0;
+}
+
static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *params)
{
@@ -441,9 +474,9 @@
runtime->stop_threshold = runtime->buffer_size;
runtime->silence_threshold = 0;
runtime->silence_size = 0;
- runtime->boundary = runtime->buffer_size;
- while (runtime->boundary * 2 <= LONG_MAX - runtime->buffer_size)
- runtime->boundary *= 2;
+ err = calc_boundary(runtime);
+ if (err < 0)
+ goto _error;
snd_pcm_timer_resolution_change(substream);
runtime->status->state = SNDRV_PCM_STATE_SETUP;
