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From: Takashi Iwai <tiwai@suse.de>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Fabio Estevam <fabio.estevam@freescale.com>,
	alsa-devel@alsa-project.org, dri-devel@lists.freedesktop.org,
	Jaroslav Kysela <perex@perex.cz>, Mark Brown <broonie@kernel.org>,
	Yakir Yang <ykk@rock-chips.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC v2 10/13] sound/core: add DRM ELD helper
Date: Sun, 05 Apr 2015 18:46:13 +0200
Message-ID: <s5h4mouy14a.wl-tiwai@suse.de> (raw)
In-Reply-To: <20150405162034.GH13898@n2100.arm.linux.org.uk>

At Sun, 5 Apr 2015 17:20:34 +0100,
Russell King - ARM Linux wrote:
> 
> On Sun, Apr 05, 2015 at 05:57:09PM +0200, Takashi Iwai wrote:
> > > diff --git a/include/sound/pcm_drm_eld.h b/include/sound/pcm_drm_eld.h
> > > new file mode 100644
> > > index 000000000000..93357b25d2e2
> > > --- /dev/null
> > > +++ b/include/sound/pcm_drm_eld.h
> > > @@ -0,0 +1,6 @@
> > > +#ifndef __SOUND_PCM_DRM_ELD_H
> > > +#define __SOUND_PCM_DRM_ELD_H
> > > +
> > > +int snd_pcm_hw_constraint_eld(struct snd_pcm_runtime *runtime, void *eld);
> > > +
> > > +#endif
> > 
> > IMO, a single line of function declaration can be merged to
> > sound/pcm.h.
> 
> Ok.
> 
> > > diff --git a/sound/core/Kconfig b/sound/core/Kconfig
> > > index 313f22e9d929..b534c8a6046b 100644
> > > --- a/sound/core/Kconfig
> > > +++ b/sound/core/Kconfig
> > > @@ -6,6 +6,9 @@ config SND_PCM
> > >  	tristate
> > >  	select SND_TIMER
> > >  
> > > +config SND_PCM_ELD
> > > +	bool
> > 
> > I don't mind much adding this one, but a new Kconfig is always a
> > question.  I'd like to hear other's opinion, too.
> 
> That's more a question whether you want it always included in the build
> or not, especially as it is dependent on DRM header files.

OK, then it makes sense to split.


> > > +printk("%s: r %d-%d c %d-%d m %x\n", __func__, r->min, r->max, c->min, c->max, rate_mask);
> > 
> > I guess this will be removed in the final version? ;)
> 
> Of course.
> 
> > > +static int eld_limit_channels(struct snd_pcm_hw_params *params,
> > > +			      struct snd_pcm_hw_rule *rule)
> > > +{
> > > +	struct snd_interval *var = hw_param_interval(params, rule->var);
> > > +	struct snd_interval t = { .min = 1, .max = 2, .integer = 1, };
> > > +	unsigned int i;
> > > +	const u8 *sad, *eld = rule->private;
> > > +
> > > +	sad = drm_eld_sad(eld);
> > > +	if (sad) {
> > > +		for (i = drm_eld_sad_count(eld); i > 0; i--, sad += 3) {
> > > +			switch (sad[0] & 0x78) {
> > > +			case 0x08:
> > > +				t.max = max(t.max, (sad[0] & 7) + 1u);
> > > +				break;
> > 
> > What about the minimal channel?
> 
> There isn't a minimum.  The SAD describes only the _maximum_ number of
> channels.  For example, if a TV supports 5.1 audio, at 32, 44.1 and 48
> kHz, it can do that with just one SAD entry which indicates support for
> six channels of audio at those sample rates.  However, it will happily
> accept 2 channel audio at those sample rates too.

Alright, I remembered wrong.  I took a look at the existing HD-audio
ELD parser code, and it also handles only the max channels.

> > Ideally, we should either give a list of channel numbers or process
> > the hw_constraints dynamically to narrow the min/max matching with the
> > eld.
> 
> The ELD can change as a result of the HDMI sink deciding to change its
> EDID (it does happen) or if the device is unplugged and re-plugged.  If
> I wanted to restrict the maximum channel/rates by building some sort of
> table, I'd do this at open time and avoid the complexity of having rule
> callbacks.

Right, this is the easiest approach.

> Since (afaik) ALSA has a lack of support for dynamic reconfiguration
> according to the attached device changing, the best we can do without
> a huge amount of re-work of HDMI support across all adapters is to
> process the capabilities of the attached device at prepare time
> according to the current capabilities.

Yeah, reconfiguration is tricky.  BTW, how is the HDMI unplug handled
during playback?

> Implementing dynamic reconfiguration in ALSA is not something I want to
> get involved with, and as we /already/ have HDMI support merged in the
> kernel, this is not a blocker for at least trying to get some semblence
> of sanity, rather than having every driver re-implementing stuff like
> this.

Well, I didn't mean about the dynamic reconfiguration.  I thought of
rather min/max pairs, but it was just a wrong assumption.  Scratch
it.

One another question: don't we need to deal with the sample bits in
sad[2]?


Takashi
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  reply index

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-02  9:20 [RFC v2 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-04-02  9:21 ` [PATCH RFC v2 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-04-02  9:21 ` [PATCH RFC v2 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-04-02  9:21 ` [PATCH RFC v2 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-04-02  9:21 ` [PATCH RFC v2 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-04-02  9:21 ` [PATCH RFC v2 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-04-02  9:21 ` [PATCH RFC v2 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-04-02  9:21 ` [PATCH RFC v2 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-04-02  9:22 ` [PATCH RFC v2 09/13] drm/edid: add function to help find SADs Russell King
2015-04-02  9:22 ` [PATCH RFC v2 10/13] sound/core: add DRM ELD helper Russell King
2015-04-05 15:57   ` Takashi Iwai
2015-04-05 16:20     ` Russell King - ARM Linux
2015-04-05 16:46       ` Takashi Iwai [this message]
2015-04-05 17:26         ` Russell King - ARM Linux
2015-05-06 17:02           ` Anssi Hannula
2015-05-07 10:41             ` Russell King - ARM Linux
2015-05-07 11:11               ` Lars-Peter Clausen
2015-05-08 10:56           ` [alsa-devel] " Jyri Sarha
2015-05-08 11:42             ` Russell King - ARM Linux
2015-05-05 22:35     ` Mark Brown
2015-05-06  8:58       ` Liam Girdwood
2015-05-08 13:16   ` [alsa-devel] " Jyri Sarha
2015-05-08 13:27     ` Russell King - ARM Linux
2015-05-08 13:37       ` Jyri Sarha
2015-04-02  9:22 ` [PATCH RFC v2 11/13] sound/core: add IEC958 channel status helper Russell King
2015-04-02  9:22 ` [PATCH RFC v2 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-04-02  9:22 ` [PATCH RFC v2 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-09 10:25 ` [PATCH v3 0/13] dw_hdmi cleanups, audio preparation, helpers and ahb audio support Russell King - ARM Linux
2015-05-09 10:25   ` [PATCH 01/13] drm: imx/dw_hdmi: move phy comments Russell King
2015-05-09 10:26   ` [PATCH 02/13] drm: bridge/dw_hdmi: clean up phy configuration Russell King
2015-05-22 15:19     ` Yakir
2015-05-09 10:26   ` [PATCH 03/13] drm: bridge/dw_hdmi: clean up hdmi_set_clk_regenerator() Russell King
2015-05-22 15:22     ` Yakir
2015-05-09 10:26   ` [PATCH 04/13] drm: bridge/dw_hdmi: use drm_hdmi_avi_infoframe_from_display_mode() Russell King
2015-05-09 10:26   ` [PATCH 05/13] drm: bridge/dw_hdmi: simplify hdmi_config_AVI() a little Russell King
2015-05-09 10:26   ` [PATCH 06/13] drm: bridge/dw_hdmi: remove mhsyncpolarity/mvsyncpolarity/minterlaced Russell King
2015-05-09 10:26   ` [PATCH 07/13] drm: bridge/dw_hdmi: introduce interface to setting sample rate Russell King
2015-05-22 15:26     ` Yakir
2015-05-09 10:26   ` [PATCH 08/13] drm: bridge/dw_hdmi: introduce interfaces to enable and disable audio Russell King
2015-05-22 15:28     ` Yakir
2015-05-09 10:26   ` [PATCH 09/13] drm/edid: add function to help find SADs Russell King
2015-05-09 10:26   ` [PATCH 10/13] sound/core: add DRM ELD helper Russell King
2015-05-22 12:20     ` [alsa-devel] " Mark Brown
2015-05-22 13:15       ` Russell King - ARM Linux
2015-05-22 13:30         ` Takashi Iwai
2015-05-22 13:53           ` Russell King - ARM Linux
2015-05-22 13:54             ` Takashi Iwai
2015-05-22 14:00               ` Russell King - ARM Linux
2015-05-22 14:02                 ` Takashi Iwai
2015-05-22 14:05                   ` Takashi Iwai
2015-05-22 16:12                     ` Russell King - ARM Linux
2015-05-09 10:26   ` [PATCH 11/13] sound/core: add IEC958 channel status helper Russell King
2015-05-22 12:40     ` Mark Brown
2015-05-09 10:26   ` [PATCH 12/13] drm: bridge/dw_hdmi-ahb-audio: add audio driver Russell King
2015-05-09 16:49     ` [alsa-devel] " Anssi Hannula
2015-05-09 16:55       ` Russell King - ARM Linux
2015-05-09 17:07         ` Anssi Hannula
2015-05-09 17:40           ` Russell King - ARM Linux
2015-05-09 17:53             ` Russell King - ARM Linux
2015-05-09 17:55             ` Anssi Hannula
2015-05-09 18:11               ` Russell King - ARM Linux
2015-05-10 18:59                 ` Anssi Hannula
2015-05-10 19:33                   ` Russell King - ARM Linux
2015-05-10 20:47                     ` Anssi Hannula
2015-05-11 15:58                     ` Mark Brown
2015-05-09 10:26   ` [PATCH 13/13] drm: bridge/dw_hdmi-ahb-audio: parse ELD from HDMI driver Russell King
2015-05-27 10:43     ` Daniel Vetter
2015-05-27 11:43       ` Mark Brown
2015-05-27 17:31       ` Russell King - ARM Linux
2015-05-27 21:29         ` Daniel Vetter
2015-05-27 21:44           ` Russell King - ARM Linux
2015-05-28  6:43             ` Daniel Vetter
2015-05-28  4:56         ` [alsa-devel] " Takashi Iwai

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