Em Wed, 02 Mar 2016 12:34:42 +0200 Laurent Pinchart <laurent.pinch...@ideasonboard.com> escreveu:
> Hi Mauro, > > Thank you for the summary. > > On Friday 26 February 2016 09:13:17 Mauro Carvalho Chehab wrote: > > We had some discussions on Feb, 12 about how to represent connectors via > > the Media Controller: > > https://linuxtv.org/irc/irclogger_log/v4l?date=2016-02-12,Fri&sel=31#l27 > > > > We tried to finish those discussions on the last two weeks, but people > > doesn't seem to be available at the same time for the discussions. So, > > let's proceed with the discussions via e-mail. > > > > So, I'd like to do such discussions via e-mail, as we need to close > > this question next week. > > > > QUESTION: > > ======== > > > > How to represent the hardware connection for inputs (and outputs) like: > > - Composite TV video; > > - stereo analog audio; > > - S-Video; > > - HDMI > > > > Problem description: > > =================== > > > > During the MC summit last year, we decided to add an entity called > > "connector" for such things. So, we added, so far, 3 types of > > connectors: > > > > #define MEDIA_ENT_F_CONN_RF (MEDIA_ENT_F_BASE + 10001) > > #define MEDIA_ENT_F_CONN_SVIDEO (MEDIA_ENT_F_BASE + 10002) > > #define MEDIA_ENT_F_CONN_COMPOSITE (MEDIA_ENT_F_BASE + 10003) > > > > However, while implementing it, we saw that the mapping on hardware > > is actually more complex, as one physical connector may have multiple > > signals with can eventually used on a different way. > > > > One simple example of this is the S-Video connector. It has internally > > two video streams, one for chrominance and another one for luminance. > > > > It is very common for vendors to ship devices with a S-Video input > > and a "S-Video to RCA" cable. > > > > At the driver's level, drivers need to know if such cable is > > plugged, as they need to configure a different input setting to > > enable either S-Video or composite decoding. > > > > So, the V4L2 API usually maps "S-Video" on a different input > > than "Composite over S-Video". This can be seen, for example, at the > > saa7134 driver, who gained recently support for MC. > > > > Additionally, it is interesting to describe the physical aspects > > of the connector (color, position, label, etc). > > > > Proposal: > > ======== > > > > It seems that there was an agreement that the physical aspects of > > the connector should be mapped via the upcoming properties API, > > with the properties present only when it is possible to find them > > in the hardware. > > Agreed for most of them, I'm still unsure about the connector type, but > that's > probably a detail. > > > So, it seems that all such properties should be optional. > > > > However, we didn't finish the meeting, as we ran out of time. Yet, > > I guess the last proposal there fulfills the requirements. So, > > let's focus our discussions on it. So, let me formulate it as a > > proposal > > > > We should represent the entities based on the inputs. So, for the > > already implemented entities, we'll have, instead: > > > > #define MEDIA_ENT_F_INPUT_RF (MEDIA_ENT_F_BASE + 10001) > > #define MEDIA_ENT_F_INPUT_SVIDEO (MEDIA_ENT_F_BASE + 10002) > > #define MEDIA_ENT_F_INPUT_COMPOSITE (MEDIA_ENT_F_BASE + 10003) > > > > The MEDIA_ENT_F_INPUT_RF and MEDIA_ENT_F_INPUT_COMPOSITE will have > > just one sink PAD each, as they carry just one signal. As we're > > describing the logical input, it doesn't matter the physical > > connector type. So, except for re-naming the define, nothing > > changes for them. > > > > Devices with S-Video input will have one MEDIA_ENT_F_INPUT_SVIDEO > > per each different S-Video input. Each one will have two sink pads, > > one for the Y signal and another for the C signal. > > > > So, a device like Terratec AV350, that has one Composite and one > > S-Video input[1] would be represented as: > > https://mchehab.fedorapeople.org/terratec_av350-modified.png > > > > > > [1] Physically, it has a SCART connector that could be enabled > > via a physical switch, but logically, the device will still switch > > from S-Video over SCART or composite over SCART. > > > > More complex devices would be represented like: > > https://hverkuil.home.xs4all.nl/adv7604.png > > https://hverkuil.home.xs4all.nl/adv7842.png > > > > NOTE: > > > > The labels at the PADs currently can't be represented, but the > > idea is adding it as a property via the upcoming properties API. > > Whether to add labels to pads, and more generically how to differentiate them > from userspace, is an interesting question. I'd like to decouple it from the > connectors entities discussion if possible, in such a way that using labels > wouldn't be required to leave the discussion open on that topic. If we > foresee > a dependency on labels for pads then we should open that discussion now. We can postpone such discussion. PAD labels are not needed for what we have so far (RF, Composite, S-Video). Still, I think that we'll need it by the time we add connector support for more complex connector types, like HDMI. > > > Anyone disagree? > > I'll reply one of the later mails in this thread in a minute about this to > capture Javier and Hans' inputs. Ok. -- Thanks, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
