Re: [PATCH 2/4] ALSA: hda - add DP mst verb support

[Takashi Iwai <tiwai@suse.de>]

On Mon, 07 Mar 2016 15:57:44 +0100,
libin.yang@linux.intel.com wrote:
> 
> +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;
> +
> +	/* If Device List Length is 0, the pin is not multi stream capable.
> +	 */
> +	if ((snd_hda_get_num_devices(codec, nid) + 1) == 0)
> +		return 0;

I don't understand what this code is for.  Why +1?

> +
> +	/* Behavior of setting index being equal to or greater than
> +	 * Device List Length is not predictable
> +	 */
> +	if ((snd_hda_get_num_devices(codec, nid) + 1) <= dev_id)
> +		return 0;

Ditto.  And, calling the same function twice?


thanks,

Takashi