[alsa-devel] [PATCH] aplay: support no period wakeup option in argument
In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag
Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com --- aplay/aplay.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/aplay/aplay.c b/aplay/aplay.c index efc1eb4cae3a..4f562bfe2884 100644 --- a/aplay/aplay.c +++ b/aplay/aplay.c @@ -137,6 +137,7 @@ static int use_strftime = 0; volatile static int recycle_capture_file = 0; static long term_c_lflag = -1; static int dump_hw_params = 0; +static int no_period_wakeup = 0;
static int fd = -1; static off64_t pbrec_count = LLONG_MAX, fdcount; @@ -243,6 +244,7 @@ _("Usage: %s [OPTION]... [FILE]...\n" " --use-strftime apply the strftime facility to the output file name\n" " --dump-hw-params dump hw_params of the device\n" " --fatal-errors treat all errors as fatal\n" +" --no-period-wakeup set no period wakeup flag if necessary\n" ) , command); printf(_("Recognized sample formats are:")); @@ -429,6 +431,7 @@ enum { OPT_USE_STRFTIME, OPT_DUMP_HWPARAMS, OPT_FATAL_ERRORS, + OPT_NO_PERIOD_WAKEUP, };
/* @@ -516,6 +519,7 @@ int main(int argc, char *argv[]) {"interactive", 0, 0, 'i'}, {"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS}, {"fatal-errors", 0, 0, OPT_FATAL_ERRORS}, + {"no-period-wakeup", 0, 0, OPT_NO_PERIOD_WAKEUP}, #ifdef CONFIG_SUPPORT_CHMAP {"chmap", 1, 0, 'm'}, #endif @@ -799,6 +803,9 @@ int main(int argc, char *argv[]) case OPT_FATAL_ERRORS: fatal_errors = 1; break; + case OPT_NO_PERIOD_WAKEUP: + no_period_wakeup = 1; + break; #ifdef CONFIG_SUPPORT_CHMAP case 'm': channel_map = snd_pcm_chmap_parse_string(optarg); @@ -1396,6 +1403,12 @@ static void set_params(void) &buffer_frames); } assert(err >= 0); + + if (no_period_wakeup) { + err = snd_pcm_hw_params_set_period_wakeup(handle, params, 0); + assert(err >= 0); + } + monotonic = snd_pcm_hw_params_is_monotonic(params); can_pause = snd_pcm_hw_params_can_pause(params); err = snd_pcm_hw_params(handle, params);
Hi,
On Wed, Dec 26, 2018 at 11:28:11AM +0000, S.j. Wang wrote:
In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag
Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com
aplay/aplay.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/aplay/aplay.c b/aplay/aplay.c index efc1eb4cae3a..4f562bfe2884 100644 --- a/aplay/aplay.c +++ b/aplay/aplay.c @@ -137,6 +137,7 @@ static int use_strftime = 0; volatile static int recycle_capture_file = 0; static long term_c_lflag = -1; static int dump_hw_params = 0; +static int no_period_wakeup = 0;
static int fd = -1; static off64_t pbrec_count = LLONG_MAX, fdcount; @@ -243,6 +244,7 @@ _("Usage: %s [OPTION]... [FILE]...\n" " --use-strftime apply the strftime facility to the output file name\n" " --dump-hw-params dump hw_params of the device\n" " --fatal-errors treat all errors as fatal\n" +" --no-period-wakeup set no period wakeup flag if necessary\n" ) , command); printf(_("Recognized sample formats are:")); @@ -429,6 +431,7 @@ enum { OPT_USE_STRFTIME, OPT_DUMP_HWPARAMS, OPT_FATAL_ERRORS,
- OPT_NO_PERIOD_WAKEUP,
};
/* @@ -516,6 +519,7 @@ int main(int argc, char *argv[]) {"interactive", 0, 0, 'i'}, {"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS}, {"fatal-errors", 0, 0, OPT_FATAL_ERRORS},
{"no-period-wakeup", 0, 0, OPT_NO_PERIOD_WAKEUP},#ifdef CONFIG_SUPPORT_CHMAP {"chmap", 1, 0, 'm'}, #endif @@ -799,6 +803,9 @@ int main(int argc, char *argv[]) case OPT_FATAL_ERRORS: fatal_errors = 1; break;
case OPT_NO_PERIOD_WAKEUP:no_period_wakeup = 1;break;#ifdef CONFIG_SUPPORT_CHMAP case 'm': channel_map = snd_pcm_chmap_parse_string(optarg); @@ -1396,6 +1403,12 @@ static void set_params(void) &buffer_frames); } assert(err >= 0);
- if (no_period_wakeup) {
err = snd_pcm_hw_params_set_period_wakeup(handle, params, 0);assert(err >= 0);- }
- monotonic = snd_pcm_hw_params_is_monotonic(params); can_pause = snd_pcm_hw_params_can_pause(params); err = snd_pcm_hw_params(handle, params);
-- 1.9.1
As of v4.21-rc1, runtime of PCM substream can't run no_period_wakeup mode unless two conditions are satisfied[1]: - driver supports SNDRV_PCM_INFO_NO_PERIOD_WAKEUP - PCM applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP flag to hardware parameter structure.
Neither alsa-lib nor the most of existent userspace applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP without explicit call of helper API. In this point, I can get your intention for this patch. If a driver just supports no_period_wakeup mode, such driver can't work well.
However, such driver is problematic because apparently it can not run with many existent userspace applications and alsa-lib. Before applying this patch, we have enough discussion to prevent problems to introduce such problematic drivers into Linux sound subsystem, in my opinion.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/c...
Regards
Takashi Sakamoto
Hi
-----Original Message----- From: Takashi Sakamoto o-takashi@sakamocchi.jp Sent: Wednesday, December 26, 2018 9:35 PM
Hi,
On Wed, Dec 26, 2018 at 11:28:11AM +0000, S.j. Wang wrote:
In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag
Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com
aplay/aplay.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/aplay/aplay.c b/aplay/aplay.c index efc1eb4cae3a..4f562bfe2884 100644 --- a/aplay/aplay.c +++ b/aplay/aplay.c @@ -137,6 +137,7 @@ static int use_strftime = 0; volatile static int recycle_capture_file = 0; static long term_c_lflag = -1; static int dump_hw_params = 0; +static int no_period_wakeup = 0;
static int fd = -1; static off64_t pbrec_count = LLONG_MAX, fdcount; @@ -243,6 +244,7
@@
_("Usage: %s [OPTION]... [FILE]...\n" " --use-strftime apply the strftime facility to the output file name\n" " --dump-hw-params dump hw_params of the device\n" " --fatal-errors treat all errors as fatal\n" +" --no-period-wakeup set no period wakeup flag if necessary\n" ) , command); printf(_("Recognized sample formats are:")); @@ -429,6 +431,7 @@ enum { OPT_USE_STRFTIME, OPT_DUMP_HWPARAMS, OPT_FATAL_ERRORS,
- OPT_NO_PERIOD_WAKEUP,
};
/* @@ -516,6 +519,7 @@ int main(int argc, char *argv[]) {"interactive", 0, 0, 'i'}, {"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS}, {"fatal-errors", 0, 0, OPT_FATAL_ERRORS},
{"no-period-wakeup", 0, 0, OPT_NO_PERIOD_WAKEUP},#ifdef CONFIG_SUPPORT_CHMAP {"chmap", 1, 0, 'm'}, #endif @@ -799,6 +803,9 @@ int main(int argc, char *argv[]) case OPT_FATAL_ERRORS: fatal_errors = 1; break;
case OPT_NO_PERIOD_WAKEUP:no_period_wakeup = 1;break;#ifdef CONFIG_SUPPORT_CHMAP case 'm': channel_map =
snd_pcm_chmap_parse_string(optarg);
@@ -1396,6 +1403,12 @@ static void set_params(void) &buffer_frames); } assert(err >= 0);
- if (no_period_wakeup) {
err = snd_pcm_hw_params_set_period_wakeup(handle,params, 0);
assert(err >= 0);- }
- monotonic = snd_pcm_hw_params_is_monotonic(params); can_pause = snd_pcm_hw_params_can_pause(params); err = snd_pcm_hw_params(handle, params);
-- 1.9.1
As of v4.21-rc1, runtime of PCM substream can't run no_period_wakeup mode unless two conditions are satisfied[1]:
- driver supports SNDRV_PCM_INFO_NO_PERIOD_WAKEUP
- PCM applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP
flag to hardware parameter structure.
Neither alsa-lib nor the most of existent userspace applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP without explicit call of helper API. In this point, I can get your intention for this patch. If a driver just supports no_period_wakeup mode, such driver can't work well.
However, such driver is problematic because apparently it can not run with many existent userspace applications and alsa-lib. Before applying this patch, we have enough discussion to prevent problems to introduce such problematic drivers into Linux sound subsystem, in my opinion.
What is helper API? I found that you have a similar function in axfer/xfer-libasound.c, Which is disable_period_wakeup(). Do you think I need to porting this function to Aplay?
Best regards Wang shengjiu
[1] https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit. kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftiwai%2Fsound.git%2 Ftree%2Fsound%2Fcore%2Fpcm_native.c%3Fh%3Dsound-4.21- rc1%23n727&data=02%7C01%7Cshengjiu.wang%40nxp.com%7Cdaa8cb 93830245f7b27108d66b36fe91%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C 0%7C0%7C636814281289991663&sdata=Qv2Jfrd2qXc91gpwJhu28bhMC SJ5%2FgZJWDzP0gDT0Ws%3D&reserved=0
Regards
Takashi Sakamoto
On Thu, Dec 27, 2018 at 02:13:28AM +0000, S.j. Wang wrote:
-----Original Message----- From: Takashi Sakamoto o-takashi@sakamocchi.jp Sent: Wednesday, December 26, 2018 9:35 PM
Hi,
On Wed, Dec 26, 2018 at 11:28:11AM +0000, S.j. Wang wrote:
In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag
Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com
aplay/aplay.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/aplay/aplay.c b/aplay/aplay.c index efc1eb4cae3a..4f562bfe2884 100644 --- a/aplay/aplay.c +++ b/aplay/aplay.c @@ -137,6 +137,7 @@ static int use_strftime = 0; volatile static int recycle_capture_file = 0; static long term_c_lflag = -1; static int dump_hw_params = 0; +static int no_period_wakeup = 0;
static int fd = -1; static off64_t pbrec_count = LLONG_MAX, fdcount; @@ -243,6 +244,7
@@
_("Usage: %s [OPTION]... [FILE]...\n" " --use-strftime apply the strftime facility to the output file name\n" " --dump-hw-params dump hw_params of the device\n" " --fatal-errors treat all errors as fatal\n" +" --no-period-wakeup set no period wakeup flag if necessary\n" ) , command); printf(_("Recognized sample formats are:")); @@ -429,6 +431,7 @@ enum { OPT_USE_STRFTIME, OPT_DUMP_HWPARAMS, OPT_FATAL_ERRORS,
- OPT_NO_PERIOD_WAKEUP,
};
/* @@ -516,6 +519,7 @@ int main(int argc, char *argv[]) {"interactive", 0, 0, 'i'}, {"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS}, {"fatal-errors", 0, 0, OPT_FATAL_ERRORS},
{"no-period-wakeup", 0, 0, OPT_NO_PERIOD_WAKEUP},#ifdef CONFIG_SUPPORT_CHMAP {"chmap", 1, 0, 'm'}, #endif @@ -799,6 +803,9 @@ int main(int argc, char *argv[]) case OPT_FATAL_ERRORS: fatal_errors = 1; break;
case OPT_NO_PERIOD_WAKEUP:no_period_wakeup = 1;break;#ifdef CONFIG_SUPPORT_CHMAP case 'm': channel_map =
snd_pcm_chmap_parse_string(optarg);
@@ -1396,6 +1403,12 @@ static void set_params(void) &buffer_frames); } assert(err >= 0);
- if (no_period_wakeup) {
err = snd_pcm_hw_params_set_period_wakeup(handle,params, 0);
assert(err >= 0);- }
- monotonic = snd_pcm_hw_params_is_monotonic(params); can_pause = snd_pcm_hw_params_can_pause(params); err = snd_pcm_hw_params(handle, params);
-- 1.9.1
As of v4.21-rc1, runtime of PCM substream can't run no_period_wakeup mode unless two conditions are satisfied[1]:
- driver supports SNDRV_PCM_INFO_NO_PERIOD_WAKEUP
- PCM applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP
flag to hardware parameter structure.
Neither alsa-lib nor the most of existent userspace applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP without explicit call of helper API. In this point, I can get your intention for this patch. If a driver just supports no_period_wakeup mode, such driver can't work well.
However, such driver is problematic because apparently it can not run with many existent userspace applications and alsa-lib. Before applying this patch, we have enough discussion to prevent problems to introduce such problematic drivers into Linux sound subsystem, in my opinion.
What is helper API? I found that you have a similar function in axfer/xfer-libasound.c, Which is disable_period_wakeup(). Do you think I need to porting this function to Aplay?
I focus on your intention itself instead of change of aplay. Here, I refer your commit description:
"In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag"
In my understanding, your intention is a kind of driver added yet in mainline. The driver doesn't adopt period wakeup. It just support no-period-wakeup. Thus the driver works without any periodical hardware/software IRQs.
At present, the feature, no-period-wakeup is an option of PCM substream. This means that all of in-kernel drivers _should_ adopt period wakeup at first. Then, if possible, it can implement no-period-wakeup with the optional flag.
An addition of driver which support no-period-wakeup only brings problems to existing applications. For example, execution of ioctl(2) with SNDRV_PCM_IOCTL_[READ|WRITE][I|N] can bring below message:
"%s write error (DMA or IRQ trouble?)"
This is output in 'wait_for_avail()' of 'sound/core/pcm_lib.c'[1]. This is because nothing awaken up a task of the execution. With normal drivers, the task is awakened by handlers on any IRQ context.
ALSA drivers should work with such applications, thus it's not good idea to develop for such drivers. In a case that hardware has no feature to generate periodical IRQs, kernel timer or hrtimer can be available to achieve 'pseudo' period wakeup for such drivers.
If you wish for drivers which don't achieve period wakeup, it's better to have enough discussion to change behaviour of ALSA PCM core at first, then work for aplay next.
Please inform me if I misread in your description.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/tree/sound/c...
Thanks
Takashi Sakamoto
Hi
-----Original Message----- From: Takashi Sakamoto o-takashi@sakamocchi.jp Sent: Thursday, December 27, 2018 12:29 PM
On Thu, Dec 27, 2018 at 02:13:28AM +0000, S.j. Wang wrote:
-----Original Message----- From: Takashi Sakamoto o-takashi@sakamocchi.jp Sent: Wednesday, December 26, 2018 9:35 PM
Hi,
On Wed, Dec 26, 2018 at 11:28:11AM +0000, S.j. Wang wrote:
In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag
Signed-off-by: Shengjiu Wang shengjiu.wang@nxp.com
aplay/aplay.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/aplay/aplay.c b/aplay/aplay.c index efc1eb4cae3a..4f562bfe2884 100644 --- a/aplay/aplay.c +++ b/aplay/aplay.c @@ -137,6 +137,7 @@ static int use_strftime = 0; volatile static int recycle_capture_file = 0; static long term_c_lflag = -1; static int dump_hw_params = 0; +static int no_period_wakeup = 0;
static int fd = -1; static off64_t pbrec_count = LLONG_MAX, fdcount; @@ -243,6 +244,7
@@
_("Usage: %s [OPTION]... [FILE]...\n" " --use-strftime apply the strftime facility to the output file
name\n"
" --dump-hw-params dump hw_params of the device\n" " --fatal-errors treat all errors as fatal\n" +" --no-period-wakeup set no period wakeup flag if necessary\n" ) , command); printf(_("Recognized sample formats are:")); @@ -429,6 +431,7 @@ enum { OPT_USE_STRFTIME, OPT_DUMP_HWPARAMS, OPT_FATAL_ERRORS,
- OPT_NO_PERIOD_WAKEUP,
};
/* @@ -516,6 +519,7 @@ int main(int argc, char *argv[]) {"interactive", 0, 0, 'i'}, {"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS}, {"fatal-errors", 0, 0, OPT_FATAL_ERRORS},
{"no-period-wakeup", 0, 0, OPT_NO_PERIOD_WAKEUP},#ifdef CONFIG_SUPPORT_CHMAP {"chmap", 1, 0, 'm'}, #endif @@ -799,6 +803,9 @@ int main(int argc, char *argv[]) case OPT_FATAL_ERRORS: fatal_errors = 1; break;
case OPT_NO_PERIOD_WAKEUP:no_period_wakeup = 1;break;#ifdef CONFIG_SUPPORT_CHMAP case 'm': channel_map =
snd_pcm_chmap_parse_string(optarg);
@@ -1396,6 +1403,12 @@ static void set_params(void) &buffer_frames); } assert(err >= 0);
- if (no_period_wakeup) {
err = snd_pcm_hw_params_set_period_wakeup(handle,params, 0);
assert(err >= 0);- }
- monotonic = snd_pcm_hw_params_is_monotonic(params); can_pause = snd_pcm_hw_params_can_pause(params); err = snd_pcm_hw_params(handle, params);
-- 1.9.1
As of v4.21-rc1, runtime of PCM substream can't run no_period_wakeup mode unless two conditions are satisfied[1]:
- driver supports SNDRV_PCM_INFO_NO_PERIOD_WAKEUP
- PCM applications set
SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP
flag to hardware parameter structure.
Neither alsa-lib nor the most of existent userspace applications set SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP without explicit call of
helper
API. In this point, I can get your intention for this patch. If a driver just supports no_period_wakeup mode, such driver can't work
well.
However, such driver is problematic because apparently it can not run with many existent userspace applications and alsa-lib. Before applying this patch, we have enough discussion to prevent problems to introduce such problematic drivers into Linux sound subsystem, in
my opinion.
What is helper API? I found that you have a similar function in axfer/xfer-libasound.c, Which is disable_period_wakeup(). Do you think I need to porting this function to Aplay?
I focus on your intention itself instead of change of aplay. Here, I refer your commit description:
"In the case that alsa driver can't support period wakeup, we need to set the no period wakeup flag"
In my understanding, your intention is a kind of driver added yet in mainline. The driver doesn't adopt period wakeup. It just support no- period-wakeup. Thus the driver works without any periodical hardware/software IRQs.
At present, the feature, no-period-wakeup is an option of PCM substream. This means that all of in-kernel drivers _should_ adopt period wakeup at first. Then, if possible, it can implement no-period-wakeup with the optional flag.
An addition of driver which support no-period-wakeup only brings problems to existing applications. For example, execution of ioctl(2) with SNDRV_PCM_IOCTL_[READ|WRITE][I|N] can bring below message:
"%s write error (DMA or IRQ trouble?)"
This is output in 'wait_for_avail()' of 'sound/core/pcm_lib.c'[1]. This is because nothing awaken up a task of the execution. With normal drivers, the task is awakened by handlers on any IRQ context.
ALSA drivers should work with such applications, thus it's not good idea to develop for such drivers. In a case that hardware has no feature to generate periodical IRQs, kernel timer or hrtimer can be available to achieve 'pseudo' period wakeup for such drivers.
If you wish for drivers which don't achieve period wakeup, it's better to have enough discussion to change behaviour of ALSA PCM core at first, then work for aplay next.
Please inform me if I misread in your description.
Thanks for the suggestion to use timer in driver.
I still have two questions: 1. It seems the no-period-wakeup feature should be dropped for it isn't recommended By alsa, right? I still found some driver in kernel support it, what's the reason?
2. Shall we add this option in aplay for it is feature that alsa support, even it is optional?
Best regards Wang shengjiu
[1] https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit. kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftiwai%2Fsound.git%2 Ftree%2Fsound%2Fcore%2Fpcm_lib.c%23n1901&data=02%7C01%7Cshe ngjiu.wang%40nxp.com%7C333a2e780d2d4dcf000a08d66bb3d352%7C686ea 1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636814817430239208&s data=ur11k%2F1mx7U45pj4PpNZcz8M4TdHIQiHxqLszjyNTkQ%3D&reser ved=0
Thanks
Takashi Sakamoto
Hi,
On Thu, Dec 27, 2018 at 06:46:57AM +0000, S.j. Wang wrote:
I still have two questions:
- It seems the no-period-wakeup feature should be dropped for it isn't recommended By alsa, right? I still found some driver in kernel support it, what's the reason?
You can see the driver supports 'period-wakeup' runtime as well as 'no-period-wakeup' runtime. The driver likely includes a condition statement to check 'struct snd_pcm_runtime.no_period_wakeup' flag, then it switches own behaviour for both cases.
Please keep it in your mind that 'period-wakeup' runtime is a default. At present, there's no way for drivers to tell userspace applications that 'period-wakeup' runtime is not supported.
- Shall we add this option in aplay for it is feature that alsa support, even it is optional?
Initially 'no-period-wakeup' runtime was introduced to achieve timer-based scheduling model[1]. Current design of aplay is not suitable to this model in many points (e.g. value of timeout argument in each call of poll(2) system call). If adopting aplay to the model, heavy refactoring is required. For this reason, I'm not positive to your idea. It's not practical.
However, just configuring hardware parameter with 'no-period-wakeup' flag, it's possible, as you posted. In this case, you misses some issues. At least: - alsa-lib configures the flag just for non-blocking operation. - alsa-lib calls poll(2) without timeout in many parts. When configuring the flag to PCM runtime, no tasks and IRQ contexts awaken the sleep process. Therefore processing of PCM frame is blocked forever in some cases.
(A call of 'snd_pcm_sw_params_set_period_event()' expects 'hw' PCM plugin in alsa-lib to use ALSA timer interface for 'emulated' periodical wakeup, however an instance of timer is for the PCM runtime with 'no-period-wakeup' thus it can't awakens the sleep process. I think this is a bug in alsa-lib.)
[1] http://0pointer.de/blog/projects/pulse-glitch-free.html [2] https://github.com/alsa-project/alsa-utils/blob/master/axfer/xfer-libasound-...
Thanks
Takashi Sakamoto
On Thu, 27 Dec 2018 07:46:57 +0100, S.j. Wang wrote:
I still have two questions:
It seems the no-period-wakeup feature should be dropped for it isn't recommended By alsa, right? I still found some driver in kernel support it, what's the reason?
Shall we add this option in aplay for it is feature that alsa support, even it is optional?
As Sakamoto-san already mentioned, no-period-wakeup is nothing but an optional feature for very specific applications and setup, and it's still valid and useful.
The condition to use this option is: - If a hardware may perform DMA continuously on a ring buffer (a la free-wheel mode), and - Application doesn't need the wakeup from kernel at each PCM period, but it manages the stream transfer timing by itself.
aplay doesn't satisfies the latter, hence adding such a command line option makes no sense. But, it doesn't mean that no-period-wakeup is useless. It can work well for specific applications like PulseAudio.
Takashi
participants (3)
-
S.j. Wang -
Takashi Iwai -
Takashi Sakamoto