At Thu, 12 Nov 2009 12:11:17 +0100 (CET),
Jaroslav Kysela wrote:
>
> On Thu, 12 Nov 2009, Takashi Iwai wrote:
>
> > At Thu, 12 Nov 2009 11:39:12 +0100,
> > I wrote:
> >>
> >> At Thu, 12 Nov 2009 10:54:02 +0100 (CET),
> >> noreply-git@xxxxxxxxxxxxxxxx wrote:
> >>>
> >>> commit 6739046df36c7adf80c961bcba4870270e66dbf6
> >>> Author: Jaroslav Kysela <perex@xxxxxxxx>
> >>> AuthorDate: Thu Nov 12 10:15:48 2009 +0100
> >>> Commit: Jaroslav Kysela <perex@xxxxxxxx>
> >>> CommitDate: Thu Nov 12 10:51:48 2009 +0100
> >>>
> >>> ALSA: hda - proc - add support for dynamic controls to mixer<->NID mapping
> >>>
> >>> This patch adds support for dynamically created controls to proc codec file
> >>> (Control: lines).
> >>>
> >>> Signed-off-by: Jaroslav Kysela <perex@xxxxxxxx>
> >>>
> >>> commit c45b73bf328cd8ace53cf39994328cf9d6548c4f
> >>> Author: Jaroslav Kysela <perex@xxxxxxxx>
> >>> AuthorDate: Wed Nov 11 13:43:01 2009 +0100
> >>> Commit: Jaroslav Kysela <perex@xxxxxxxx>
> >>> CommitDate: Thu Nov 12 10:51:16 2009 +0100
> >>>
> >>> ALSA: hda - proc - introduce Control: lines to show mixer<->NID assignment
> >>>
> >>> This is an initial patch to show universal control<->NID assigment in
> >>> proc codec file. The change helps to debug codec related problems.
> >>>
> >>> Signed-off-by: Jaroslav Kysela <perex@xxxxxxxx>
> >>
> >> I find the second one is the nice hack, but the first (newer) one
> >> isn't good since it abuses the subdevice field of the ctl id.
> >> It is a part of API/ABI, and if we do any changes the semantics, we
> >> should define the changed behavior *beforehand* publicly.
> >
> > BTW, I don't mean that using subdevice is wrong. Instead: if we use
> > it, let's define the proper definition first. For example, define
> > (1 << 31) as the private (driver-specific) field bit in control.h.
> >
> > Actually, using the subdevice can make the change of snd_hda_add_ctl
> > easier, too. Then you don't keep nid in another field but just use
> > snd_kcontrol to retrieve the nid.
> >
> > Of course, we'd need to check the existing apps (at least our own)
> > whether subdevice is really safe to change freely, though.
>
> I think that you overlooked this code in snd_hda_add_new_ctls():
>
> if (knew->subdevice & (1<<31)) {
> nid = knew->subdevice & 0xffff;
> kctl->id.subdevice = 0;
> } else {
> nid = 0;
> }
>
> The subdevice value for nid contents will never leave the HDA code.
Yep, I overlooked that.
Takashi
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