From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mauro Carvalho Chehab Subject: Re: [patch][saa7134] do not change mute state for capturing audio Date: Tue, 19 Jul 2011 16:29:59 -0300 Message-ID: <4E25DB37.8020609@infradead.org> References: <4E19D2F7.6060803@list.ru> <4E1E05AC.2070002@infradead.org> <4E1E0A1D.6000604@list.ru> <4E1E1571.6010400@infradead.org> <4E1E8108.3060305@list.ru> <4E1F9A25.1020208@infradead.org> <4E22AF12.4020600@list.ru> <4E22CCC0.8030803@infradead.org> <4E24BEB8.4060501@redhat.com> <4E257FF5.4040401@infradead.org> <4E258B60.6010007@list.ru> <4E25906D.3020200@infradead.org> <4E259B0C.90107@list.ru> <4E25A26A.2000204@infradead.org> <4E25A7C2.3050609@list.ru> <4E25C7AE.5020503@infradead.org> <4E25CF35.7000802@list.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4E25CF35.7000802@list.ru> Sender: linux-media-owner@vger.kernel.org To: Stas Sergeev Cc: Lennart Poettering , linux-media@vger.kernel.org, "Nickolay V. Shmyrev" , Devin Heitmueller , ALSA devel List-Id: alsa-devel@alsa-project.org Em 19-07-2011 15:38, Stas Sergeev escreveu: > 19.07.2011 22:06, Mauro Carvalho Chehab wrote: >>> Unless I am mistaken, this control is usually called a >>> "Master Playback Switch" in the alsa world. >> No, you're mistaken: on most boards, you have only one volume control/switch, >> for capture. So, it would be a "master capture switch", > Well, for such a cards we don't need to export > the additional element, they are fine already. > We can rename it to "Master Capture Switch", > or may not. Adding a new volume control that changes the mute values for the other controls or renaming it don't solve anything. >> but I don't think >> that there's such alsa "generic" volume control. Even in the case where >> you have a volume control for the LINE OUT pin[1], in general, you also need to >> unmute the capture, so, it would be a "master capture and LINE OUT switch", >> and, for sure alsa currently not provide anything like that. > I think you can still call it a "Master Capture Switch", > if it enables everything. That would be wrong. >>> So, am I right that the only problem is that it is not >>> exported to the user by some drivers right now? >> No, you're mistaken again. Such "master capture and LINE OUT switch" type of control >> _is_exported_ via the V4L2 API as V4L2_CID_AUDIO_MUTE. > Sorry, I meant the _alsa_ drivers here. > So, to rephrase: > > So, am I right that the only problem is that it is not > exported to the user by some _alsa_ drivers right now? I fail to see why this would be a problem. The problem I see is that PA is trying to handle a V4L device as if it would be a normal audio capture pin, and starting a capture while the device is not ready for that, as no input or TV/radio station were selected at the time PA starts capturing. >> Some applications like mplayer don't use V4L2_CID_AUDIO_MUTE to unmute a video >> device. They assume the current behavior that starting video also unmutes audio. >> (mplayer is not symmetric with regard to the usage of this control, as it uses >> V4L2_CID_AUDIO_MUTE to mute the device after the end of a capture). >> >> So, changing the logic at the drivers will break existing applications. > I do not propose changing any V4L2 ioctls, my > change concerns only the alsa driver. > >> It is probably doable to split the mute control for the LINE OUT pin from the >> mute control of the PCM capture. Such patch would make sense, as the alsa >> capture doesn't need to touch at the line out pin, but the patch should >> let V4L2_CID_AUDIO_MUTE control to affect both LINE OUT and PCM capture >> mutes, otherwise applications will break. > That's exactly what I was talking about from the very > beginning, saying that the single control currently controls > way too much, and providing an examples about 2 separate > controls. But... I haven't found the way to implement that, > not sure of this is possible at all. :( It is doable, although it is probably not trivial. Devices with saa7130 (PCI_DEVICE_ID_PHILIPS_SAA7130) doesn't enable the alsa module, as they don't support I2S transfers, required for PCM audio. So, we need to take care only on saa7133/4/5 devices. The mute code is at saa7134-tvaudio.c, mute_input_7134() function. For saa7134, it does: if (PCI_DEVICE_ID_PHILIPS_SAA7134 == dev->pci->device) /* 7134 mute */ saa_writeb(SAA7134_AUDIO_MUTE_CTRL, mute ? SAA7134_MUTE_MASK | SAA7134_MUTE_ANALOG | SAA7134_MUTE_I2S : SAA7134_MUTE_MASK); Clearly, there are two mute flags: SAA7134_MUTE_ANALOG and SAA7134_MUTE_I2S. I2S is for PCM (as it is a digital audio interface). The other flag is for analog. So, if the device is a saa7134, it is easy to split the analog output and the PCM one. For saa7133 and saa7135, you probably need to double check at the datasheet, is is there a way to disable/enable just the I2S interface, but, from saa7134_enable_i2s(): /* Start I2S */ saa_writeb(SAA7134_I2S_AUDIO_OUTPUT, 0x11); I bet that there is some value (maybe 0?) that disables I2S transfers, muting the PCM stream. It should be tested if saa7133/5 devices accept to enable/disable PCM streams if the device is already streaming. Cheers, Mauro