Re: [alsa-utils] [PATCH] Add support for no-rewind flag in aplay utility

[Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>]

On 1/30/18 11:40 AM, Takashi Sakamoto wrote:
> Hi,
>
> On Jan 30 2018 18:34, Sriram Periyasamy wrote:
> > From: Ramesh Babu <ramesh.babu@xxxxxxxxx>
> >
> > The "no-rewind" flag is introduced in alsa.
> > Application can use this flag to assure kernel driver
> > that rewind won't be exercised. Driver could use this
> > flag to alter it's buffering scheme to optimize power
> > and performance.
> >
> > Signed-off-by: Ramesh Babu <ramesh.babu@xxxxxxxxx>
> > Signed-off-by: Sriram Periyasamy <sriramx.periyasamy@xxxxxxxxx>
> > ---
> >   aplay/aplay.c | 14 +++++++++++++-
> >   1 file changed, 13 insertions(+), 1 deletion(-)
>
> Current implementation of 'aplay' doesn't perform rewinding/forwarding,
> thus an additional of this option is surplus.

It helps tell the driver that rewinds won't be used and indirectly that 
the appl_ptr updates are passed to the hardware.
Removing the option or making the functionality unconditional removes 
the freedom to test with or without this option.

> > diff --git a/aplay/aplay.c b/aplay/aplay.c
> > index 6b740c281f8e..b50602a59024 100644
> > --- a/aplay/aplay.c
> > +++ b/aplay/aplay.c
> > @@ -108,6 +108,7 @@ static snd_pcm_stream_t stream = SND_PCM_STREAM_PLAYBACK;
> >   static int mmap_flag = 0;
> >   static int interleaved = 1;
> >   static int nonblock = 0;
> > +static int no_rewind = 0;
> >   static volatile sig_atomic_t in_aborting = 0;
> >   static u_char *audiobuf = NULL;
> >   static snd_pcm_uframes_t chunk_size = 0;
> > @@ -229,6 +230,7 @@ _("Usage: %s [OPTION]... [FILE]...\n"
> >   "-I, --separate-channels one file for each channel\n"
> >   "-i, --interactive       allow interactive operation from stdin\n"
> >   "-m, --chmap=ch1,ch2,..  Give the channel map to override or follow\n"
> > +"-w, --no-rewind         enables no rewind mode\n"
> >   "    --disable-resample  disable automatic rate resample\n"
> >   "    --disable-channels  disable automatic channel conversions\n"
> >   "    --disable-format    disable automatic format conversions\n"
> > @@ -470,7 +472,7 @@ int main(int argc, char *argv[])
> >   {
> >   	int duration_or_sample = 0;
> >   	int option_index;
> > -	static const char short_options[] = "hnlLD:qt:c:f:r:d:s:MNF:A:R:T:B:vV:IPCi"
> > +	static const char short_options[] = "hnlLD:qt:c:f:r:d:s:w:MNF:A:R:T:B:vV:IPCi"
> >   #ifdef CONFIG_SUPPORT_CHMAP
> >   		"m:"
> >   #endif
> > @@ -514,6 +516,7 @@ int main(int argc, char *argv[])
> >   		{"process-id-file", 1, 0, OPT_PROCESS_ID_FILE},
> >   		{"use-strftime", 0, 0, OPT_USE_STRFTIME},
> >   		{"interactive", 0, 0, 'i'},
> > +		{"no-rewind", 0, 0, 'w'},
> >   		{"dump-hw-params", 0, 0, OPT_DUMP_HWPARAMS},
> >   		{"fatal-errors", 0, 0, OPT_FATAL_ERRORS},
> >   #ifdef CONFIG_SUPPORT_CHMAP
> > @@ -753,6 +756,9 @@ int main(int argc, char *argv[])
> >   		case 'i':
> >   			interactive = 1;
> >   			break;
> > +		case 'w':
> > +			no_rewind = 1;
> > +			break;
> >   		case OPT_DISABLE_RESAMPLE:
> >   			open_mode |= SND_PCM_NO_AUTO_RESAMPLE;
> >   			break;
> > @@ -1396,6 +1402,12 @@ static void set_params(void)
> >   							     &buffer_frames);
> >   	}
> >   	assert(err >= 0);
> > +
> > +	if (no_rewind) {
> > +		err = snd_pcm_hw_params_set_no_rewind(handle, params, 1);
> > +		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);
>
>
> Regards
>
> Takashi Sakamoto
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@xxxxxxxxxxxxxxxx
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel

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