Hi Takashi, > -----Original Message----- > From: Takashi Iwai [mailto:tiwai@xxxxxxx] > Sent: Tuesday, March 08, 2016 12:46 AM > To: libin.yang@xxxxxxxxxxxxxxx > Cc: alsa-devel@xxxxxxxxxxxxxxxx; Lin, Mengdong; Yang, Libin > Subject: Re: [PATCH 2/4] ALSA: hda - add DP mst verb > support > > On Mon, 07 Mar 2016 15:57:44 +0100, > libin.yang@xxxxxxxxxxxxxxx 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? Sorry, it should be if ((snd_hda_get_num_devices(codec, nid)) == 0). 0 means not MST capable. Thanks for point it out. > > > + > > + /* 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? (snd_hda_get_num_devices(codec, nid) + 1) means the device entry number. If the (snd_hda_get_num_devices(codec, nid) + 1) == 3, it means there are only 3 device entries. And dev_id being 0, 1, 2 is legal. It dev_id is 3 or greater, it is illegal. Regards, Libin > > > thanks, > > Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
