[alsa-devel] [PATCH] ALSA: hda - add DP mst verb support

[Takashi Iwai]

On Wed, 13 Jan 2016 12:09:49 +0100,
libin.yang at linux.intel.com wrote:
> 
> From: Libin Yang <libin.yang at linux.intel.com>
> 
> Add snd_hda_get_dev_select() and snd_hda_set_dev_select() functions
> for DP MST audio support.
> 
> Signed-off-by: Libin Yang <libin.yang at linux.intel.com>
> ---
>  sound/pci/hda/hda_codec.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++
>  sound/pci/hda/hda_codec.h |  2 ++
>  2 files changed, 56 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index 8374188..95baaba 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -368,6 +368,60 @@ int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
>  	return devices;
>  }
>  
> +/**
> + * snd_hda_get_dev_select - get device entry select on the pin
> + * @codec: the HDA codec
> + * @nid: NID of the pin to get device entry select
> + *
> + * Get the devcie entry select on the pin. Return the device entry
> + * id selected on the pin. Return 0 means the first device entry
> + * is selected or MST is not supported.
> + */
> +int snd_hda_get_dev_select(struct hda_codec *codec, hda_nid_t nid)
> +{
> +	/* not support dp_mst will always return 0, using first dev_entry */
> +	if (!codec->dp_mst)
> +		return 0;
> +
> +	return snd_hda_codec_read(codec, nid, 0, AC_VERB_GET_DEVICE_SEL, 0);
> +}
> +EXPORT_SYMBOL_GPL(snd_hda_get_dev_select);
> +
> +/**
> + * snd_hda_set_dev_select - set device entry select on the pin
> + * @codec: the HDA codec
> + * @nid: NID of the pin to set device entry select
> + * @dev_id: device entry id to be set
> + *
> + * Set the device entry select on the pin nid.

The return code isn't clearly defined.

Other than that, it looks OK.  But I prefer merging this rather
together with its caller (unless a complex dependency exists).


thanks,

Takashi

> + */
> +int snd_hda_set_dev_select(struct hda_codec *codec, hda_nid_t nid, int dev_id)
> +{
> +	int ret, dev;
> +	unsigned long timeout;
> +
> +	/* not support dp_mst will always return 0, using first dev_entry */
> +	if (!codec->dp_mst)
> +		return 0;
> +
> +	timeout = jiffies + msecs_to_jiffies(500);
> +
> +	/* make sure the device entry selection takes effect */
> +	do {
> +		ret = snd_hda_codec_write(codec, nid, 0,
> +			AC_VERB_SET_DEVICE_SEL, dev_id);
> +		udelay(20);
> +
> +		dev = snd_hda_get_dev_select(codec, nid);
> +		if (dev == dev_id)
> +			break;
> +		msleep(20);
> +	} while (time_before(jiffies, timeout));
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(snd_hda_set_dev_select);
> +
>  /*
>   * read widget caps for each widget and store in cache
>   */
> diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
> index 373fcad..22bcad6 100644
> --- a/sound/pci/hda/hda_codec.h
> +++ b/sound/pci/hda/hda_codec.h
> @@ -349,6 +349,8 @@ int snd_hda_get_conn_index(struct hda_codec *codec, hda_nid_t mux,
>  			   hda_nid_t nid, int recursive);
>  int snd_hda_get_devices(struct hda_codec *codec, hda_nid_t nid,
>  			u8 *dev_list, int max_devices);
> +int snd_hda_get_dev_select(struct hda_codec *codec, hda_nid_t nid);
> +int snd_hda_set_dev_select(struct hda_codec *codec, hda_nid_t nid, int dev_id);
>  
>  struct hda_verb {
>  	hda_nid_t nid;
> -- 
> 1.9.1
>