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ALSA: pcm_native - fix runtime->boundary calculation

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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>
This commit is contained in:
Jaroslav Kysela 2010-01-27 18:10:13 +01:00
parent e763692578
commit 7910b4a1db
1 changed files with 36 additions and 3 deletions
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39
sound/core/pcm_native.c
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@ -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 @@ static int period_to_usecs(struct snd_pcm_runtime *runtime)
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 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
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;