From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [RFC] ASoC: snd_soc_jack for HDMI audio: does it make sense? Date: Thu, 23 Aug 2012 20:57:20 -0600 Message-ID: <5036ED90.4080508@wwwdotorg.org> References: <5032E8A5.8070108@ti.com> <1345528867.15491.12.camel@lappyti> <50342E9A.9010707@ti.com> <5036DC80.90200@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5036DC80.90200@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Ricardo Neri Cc: alsa-devel , Takashi Iwai , "Brown, Mark" , DRI development list , Peter Ujfalusi , Tomi Valkeinen , "Guiriec, Sebastien" , "Clark, Rob" , "linux-omap@vger.kernel.org" , Liam Girdwood List-Id: linux-omap@vger.kernel.org On 08/23/2012 07:44 PM, Ricardo Neri wrote: > On 08/22/2012 02:55 AM, Takashi Iwai wrote: >> At Tue, 21 Aug 2012 19:58:02 -0500, >> Ricardo Neri wrote: ... >>> Maybe the lack of audio support in drm is because the audio users should >>> not talk to drm directly but to a lower level component (omapdrm, >>> omapdss?). However, today there exists video technology supports audio >>> as well, such as DisplayPort or HDMI. Could it make more sense now to >>> provide audio support? >> >> The reason is that the audio and video handling are already separated >> in the hardware level, at least, for desktop graphics. > > Separated in what sense? Do they have separate register banks in For NVIDIA desktop GPUs, this is certainly true, and I think so for any Intel Azalia/HDA controller. The separate register banks are in different PCI functions on the chip. The Intel Azalia/HDA spec also architects specific ways that the audio and video parts interact (i.e. ELD representation of EDID data, unsolicited response messages when the video state changes, etc.) Oh, I see Takashi mentioned this below. > independent power domains? Most likely yes. > Can audio an video work with complete > independence. What happens if someone decides to power off video. Is the > audio able to continue if required? I believe audio DMA isn't affect by the video state, but I'm not 100% sure of that. >> The audio infoframe is passed via ELD to the audio controller part >> upon plug/unplugging via HD-audio unsolicited event, and the audio >> driver sets up the stuff according to the given ELD. Thus no extra >> interface between drm and ALSA was required in the kernel API level, >> so far. > > I see that the unsolicited event is used only to parse the EDID, > correct? It also notifies about the jack status. Hence, if there the > cable is disconnected the application will know and act accordingly. Is > this understanding correct? The kernel will know, and then passes the information on to user-space.