Re: [alsa-devel] [PATCH 1/7] ALSA: hda: Allow for compress stream to hdac_ext_stream assignment

[Takashi Iwai <tiwai@suse.de>]

On Tue, 17 Dec 2019 10:58:45 +0100,
Cezary Rojewski wrote:
> 
> Currently only PCM streams can enlist hdac_stream for their data
> transfer. Add cstream field to hdac_ext_stream to expose possibility of
> compress stream assignment in place of PCM one.
> Limited to HOST-type only.
> 
> Rather than copying entire hdac_ext_host_stream_assign, declare separate
> PCM and compress wrappers and reuse it for both cases.
> 
> Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
> ---
>  include/sound/hdaudio.h         |  1 +
>  include/sound/hdaudio_ext.h     |  2 ++
>  sound/hda/ext/hdac_ext_stream.c | 46 +++++++++++++++++++++++++++++----
>  3 files changed, 44 insertions(+), 5 deletions(-)
> 
> diff --git a/include/sound/hdaudio.h b/include/sound/hdaudio.h
> index e05b95e83d5a..9a8bf1eb7d69 100644
> --- a/include/sound/hdaudio.h
> +++ b/include/sound/hdaudio.h
> @@ -481,6 +481,7 @@ struct hdac_stream {
>  	struct snd_pcm_substream *substream;	/* assigned substream,
>  						 * set in PCM open
>  						 */
> +	struct snd_compr_stream *cstream;
>  	unsigned int format_val;	/* format value to be set in the
>  					 * controller and the codec
>  					 */

One might use union for pointing to either PCM or compr stream and
identify the type with some flag.

	struct hdac_stream {
		union {
			struct snd_pcm_substream *substream;
			struct snd_compr_stream *cstream;
		};
		bool is_compr;
		....

But, I'm not advocating for this.  Although this makes the stream
assignment more handy, it might lead to refer to a wrong object if you
don't check the flag properly, too.  It really depends on the code.


thanks,

Takashi
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