When executing ioctl(2) with some commands, applications can request ALSA PCM core to change appl_ptr in kernel space. Below is a list of such operations: - SNDRV_PCM_IOCTL_PREPARE - SNDRV_PCM_IOCTL_RESET - SNDRV_PCM_IOCTL_REWIND - SNDRV_PCM_IOCTL_FORWARD - SNDRV_PCM_IOCTL_WRITEI_FRAMES - SNDRV_PCM_IOCTL_WRITEN_FRAMES - SNDRV_PCM_IOCTL_READI_FRAMES - SNDRV_PCM_IOCTL_READN_FRAMES
After these operations, the value of appl_ptr should be synchronized between kernel/user spaces.
This commit adds a helper function to query status and control data without issuing the control data just in fallback from failure of control mapping.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- src/pcm/pcm_hw.c | 46 ++++++++++++++++++++++++++++++++++------------ 1 file changed, 34 insertions(+), 12 deletions(-)
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c index f03bc589..9963523c 100644 --- a/src/pcm/pcm_hw.c +++ b/src/pcm/pcm_hw.c @@ -151,6 +151,20 @@ static int sync_ptr(snd_pcm_hw_t *hw, unsigned int flags) return 0; }
+static int query_status_and_control_data(snd_pcm_hw_t *hw) +{ + if (!hw->mmap_control_fallbacked) + return 0; + + /* + * Query both of control/status data to avoid unexpected change of + * control data in kernel space. + */ + return sync_ptr1(hw, + SNDRV_PCM_SYNC_PTR_APPL | + SNDRV_PCM_SYNC_PTR_AVAIL_MIN); +} + static int snd_pcm_hw_clear_timer_queue(snd_pcm_hw_t *hw) { if (hw->period_timer_need_poll) { @@ -601,7 +615,7 @@ static int snd_pcm_hw_prepare(snd_pcm_t *pcm) SYSMSG("SNDRV_PCM_IOCTL_PREPARE failed (%i)", err); return err; } - return sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL); + return query_status_and_control_data(hw); }
static int snd_pcm_hw_reset(snd_pcm_t *pcm) @@ -613,7 +627,7 @@ static int snd_pcm_hw_reset(snd_pcm_t *pcm) SYSMSG("SNDRV_PCM_IOCTL_RESET failed (%i)", err); return err; } - return sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL); + return query_status_and_control_data(hw); }
static int snd_pcm_hw_start(snd_pcm_t *pcm) @@ -688,7 +702,7 @@ static snd_pcm_sframes_t snd_pcm_hw_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t fra SYSMSG("SNDRV_PCM_IOCTL_REWIND failed (%i)", err); return err; } - err = sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL); + err = query_status_and_control_data(hw); if (err < 0) return err; return frames; @@ -709,7 +723,7 @@ static snd_pcm_sframes_t snd_pcm_hw_forward(snd_pcm_t *pcm, snd_pcm_uframes_t fr SYSMSG("SNDRV_PCM_IOCTL_FORWARD failed (%i)", err); return err; } - err = sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL); + err = query_status_and_control_data(hw); if (err < 0) return err; return frames; @@ -805,8 +819,10 @@ static snd_pcm_sframes_t snd_pcm_hw_writei(snd_pcm_t *pcm, const void *buffer, s xferi.buf = (char*) buffer; xferi.frames = size; xferi.result = 0; /* make valgrind happy */ - err = ioctl(fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &xferi); - err = err >= 0 ? sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL) : -errno; + if (ioctl(fd, SNDRV_PCM_IOCTL_WRITEI_FRAMES, &xferi) < 0) + err = -errno; + else + err = query_status_and_control_data(hw); #ifdef DEBUG_RW fprintf(stderr, "hw_writei: frames = %li, xferi.result = %li, err = %i\n", size, xferi.result, err); #endif @@ -824,8 +840,10 @@ static snd_pcm_sframes_t snd_pcm_hw_writen(snd_pcm_t *pcm, void **bufs, snd_pcm_ memset(&xfern, 0, sizeof(xfern)); /* make valgrind happy */ xfern.bufs = bufs; xfern.frames = size; - err = ioctl(fd, SNDRV_PCM_IOCTL_WRITEN_FRAMES, &xfern); - err = err >= 0 ? sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL) : -errno; + if (ioctl(fd, SNDRV_PCM_IOCTL_WRITEN_FRAMES, &xfern) < 0) + err = -errno; + else + err = query_status_and_control_data(hw); #ifdef DEBUG_RW fprintf(stderr, "hw_writen: frames = %li, result = %li, err = %i\n", size, xfern.result, err); #endif @@ -843,8 +861,10 @@ static snd_pcm_sframes_t snd_pcm_hw_readi(snd_pcm_t *pcm, void *buffer, snd_pcm_ xferi.buf = buffer; xferi.frames = size; xferi.result = 0; /* make valgrind happy */ - err = ioctl(fd, SNDRV_PCM_IOCTL_READI_FRAMES, &xferi); - err = err >= 0 ? sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL) : -errno; + if (ioctl(fd, SNDRV_PCM_IOCTL_READI_FRAMES, &xferi) < 0) + err = -errno; + else + err = query_status_and_control_data(hw); #ifdef DEBUG_RW fprintf(stderr, "hw_readi: frames = %li, result = %li, err = %i\n", size, xferi.result, err); #endif @@ -862,8 +882,10 @@ static snd_pcm_sframes_t snd_pcm_hw_readn(snd_pcm_t *pcm, void **bufs, snd_pcm_u memset(&xfern, 0, sizeof(xfern)); /* make valgrind happy */ xfern.bufs = bufs; xfern.frames = size; - err = ioctl(fd, SNDRV_PCM_IOCTL_READN_FRAMES, &xfern); - err = err >= 0 ? sync_ptr(hw, SNDRV_PCM_SYNC_PTR_APPL) : -errno; + if (ioctl(fd, SNDRV_PCM_IOCTL_READN_FRAMES, &xfern) < 0) + err = -errno; + else + err = query_status_and_control_data(hw); #ifdef DEBUG_RW fprintf(stderr, "hw_readn: frames = %li, result = %li, err = %i\n", size, xfern.result, err); #endif