Re: [RFC PATCH] ALSA: hda: call ext hda codec link up/down if available

From: Takashi Iwai <tiwai@suse.de>
To: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Cc: alsa-devel@alsa-project.org,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Subject: Re: [RFC PATCH] ALSA: hda: call ext hda codec link up/down if available
Date: Thu, 04 Feb 2021 15:04:43 +0100	[thread overview]
Message-ID: <s5h4kis6i9w.wl-tiwai@suse.de> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2102041239160.864696@eliteleevi.tm.intel.com>

On Thu, 04 Feb 2021 11:42:20 +0100,
Kai Vehmanen wrote:
> 
> Hey,
> 
> On Thu, 4 Feb 2021, Takashi Iwai wrote:
> 
> > On Thu, 04 Feb 2021 09:07:09 +0100, Kai Vehmanen wrote:
> > > Takashi and others, this patch is a follow-up to the earlier thread about 
> > > hdac link management:
> > > https://mailman.alsa-project.org/pipermail/alsa-devel/2021-January/179715.html
> > > 
> > > We have absolutely no calls from sound/pci/hda/ to hdaudio_ext.h before
> > > this patch, so I'm wondering if this is the right approach to take. 
> > 
> > An obvious drawback by this patch is that it'll make the hda-ext code
> > always loaded whenever it's enabled, no matter whether it's really
> > used or not.
> > 
> > Maybe adding a new callback (link) in hdac_bus_ops can help?
> 
> hmm, that's true. Let me try adding a separate callback and resend for 
> review. That will look cleaner in hda_codec.c.

Thanks.

BTW, one more thing: the code link up/down isn't always paired.  It's
a bit map and only holding states.  For example, in hda_codec.c, the
link power down may happen conditionally marked in
hda_codec_runtime_suspend() while the resume always marks the link
power up.  So you'd need to check the bitmap change to perform the
refcount up/down in the hda-ext side.

Takashi