From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Takashi Iwai <tiwai@suse.de>
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, 5 Apr 2015 18:26:08 +0100 [thread overview]
Message-ID: <20150405172608.GA12732@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <s5h4mouy14a.wl-tiwai@suse.de>
On Sun, Apr 05, 2015 at 06:46:13PM +0200, Takashi Iwai wrote:
> At Sun, 5 Apr 2015 17:20:34 +0100,
> Russell King - ARM Linux wrote:
> > 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?
We don't handle it right now - and we don't have any notification to
the audio drivers that that has happened. Even if we did have such a
notification, I'm not sure what the audio driver could do with it at
the moment.
> > 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]?
It should, but I'm very wary about doing that without seeing more
examples of real SADs. Right now, all my examples only support
one SAD with either 2 channel or 6 channel audio at the standard
(basic) 32, 44.1 and 48kHz rates.
The HDMI / CEA specs are very loose in their wording about the
short audio descriptors. I've no idea whether a sink can provide
(for example) descriptors such as:
LPCM, 6 channel 32, 44.1, 48kHz
LPCM, 2 channel, 32, 44.1, 48, 96, 192kHz
or whether have to describe that as a single descriptor. I only
have two TVs to test with here.
What I'm concerned about is that when the ALSA parameter refining
starts, we start with (eg) 2-8 channels, 32-192kHz. Given that,
if we invoke the channel restriction before the rate restriction,
we would end up limiting to 2 channel at 32-192kHz. If we apply
the restrictions in the opposite order, we'd restrict to 6
channel, 32-48kHz. Neither are obviously correct in this
circumstance, and I don't really see a way to solve it given my
understanding of the way ALSA's parameter refinement works.
I suspect this is why most HDMI drivers are implemented such that
they take the maximum capabilities over all SADs, which would end
up restricting audio in the above case to: up to 6 channels, at
32, 44.1, 48, 96 and 192kHz, even though 6 channel @ 192kHz isn't
hasn't been indicated as supported.
Most of this is speculation though, based off what is in the
documentation. As I say, I don't have enough real-world examples
to get a feel for what manufacturers _actually_ do to give a hint
as to how the documentation should be interpreted.
So, maybe I should just copy what everyone else does and take the
maximum of all descriptors...
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
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next prev parent reply other threads:[~2015-04-05 17:26 UTC|newest]
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
2015-04-05 17:26 ` Russell King - ARM Linux [this message]
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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