On Thu 21 June 2012 08:53:25 Sakari Ailus wrote: > Hi Hans, > > On Wed, Jun 20, 2012 at 01:00:34PM +0200, Hans Verkuil wrote: > > On Wed 20 June 2012 12:25:09 Sakari Ailus wrote: > > > Hi Scott, > > > > > > Scott Jiang wrote: > > > >>>>>> I would expect that the combination of v4l2_mbus_framefmt + > > > >>>>>> v4l2_dv_timings > > > >>>>>> gives you the information you need. > > > >>>>>> > > > >>>>> I can solve this problem in HD, but how about SD? Add a fake > > > >>>>> dv_timings ops in SD decoder driver? > > > >>>>> > > > >>>> > > > >>>> No, you add g/s_std instead. SD timings are set through that API. It is > > > >>>> not so > > > >>>> much that you give explicit timings, but that you give the SD standard. > > > >>>> And from > > > >>>> that you can derive the timings (i.e., one for 60 Hz formats, and one for > > > >>>> 50 Hz > > > >>>> formats). > > > >>>> > > > >>> Yes, it's a solution for decoder. I can convert one by one. But how > > > >>> about sensors?They can output VGA, QVGA or any manual resolution. > > > >>> My question is why we can't add these blanking details in > > > >>> v4l2_mbus_framefmt? This structure is used to describe frame format on > > > >>> media bus. And I believe blanking data also transfer on this bus. I > > > >>> know most hardwares don't care about blanking areas, but some hardware > > > >>> such as PPI does. PPI can capture ancillary data both in herizontal > > > >>> and vertical interval. Even it works in active video only mode, it > > > >>> expects to get total timing info. > > > >> > > > >> > > > >> Since I don't know what you are trying to do, it is hard for me to give > > > >> a good answer. > > > >> > > > >> So first I'd like to know if this is related to the adv7842 chip? I think > > > >> you are talking about how this is done in general, and not specifically in > > > >> relationship to the adv7842. At least, I can't see how/why you would > > > >> hook up a sensor to the adv7842. > > > > Yes, I want to have a general solution. > > > > > > > >> > > > >> Sensor configuration is a separate topic, and something I am not an > > > >> expert on. People like Sakari Ailus and Laurent Pinchart know much > > > >> more about that than I do. > > > >> > > > >> I know that there is some support for blanking through low-level image > > > >> source > > > >> controls: > > > >> > > > >> http://hverkuil.home.xs4all.nl/spec/media.html#image-source-controls > > > >> > > > >> This is experimental and if this is insufficient for your requirements than > > > >> I suggest posting a message where you explain what you need, CC-ing the > > > >> people > > > >> I mentioned, > > > >> > > > >> Most of these APIs are quite new and by marking them as experimental we can > > > >> make changes later if it turns out it is not good enough. > > > > I remember I have discussed this topic with Sakari before but without > > > > working out a solution. > > > > In conclusion, my current solution is: > > > > if (HD) > > > > dv_timings > > > > else if (SD) > > > > fill in according to PAL/NTSC timings > > > > else > > > > get control of V4L2_CID_HBLANK/V4L2_CID_VBLANK > > > > > > > > I guess this can solve my problem. But it's a bit complicated. If > > > > v4l2_mbus_framefmt contains thes members, it's convenient and simple. > > > > > > Adding horizontal and vertical blanking as fields to struct > > > v4l2_mbus_framefmt was discussed long ago --- I even sent a patch doing > > > that AFAIR. It'd have been a simple solution, yes. The resulting > > > discussion concluded, however, that as the horizontal or vertical > > > blanking are not really a property of the image format, and generally > > > only affect timing (frame rate, they do not belong to this struct. > > > > > > Also changing them while streaming is almost always possible (except in > > > your case, I believe) whereas the rest of the fields are considered > > > static. It'd be difficult for the user to know which fields can be > > > actually changed while streamon, and which can't. > > > > > > For these reasons (AFAIR) we chose to use controls instead. > > > > > > I think the right solution to the problem when it comes to sensors, is > > > to mark these controls busy from the bridge driver if the bridge > > > hardware can't cope with changes in blanking. The control framework > > > doesn't support this currently but it might not be that much of work to > > > implement it. Such feature would definitely have to be used with care. > > > > > > Hans, what do you think? > > > > That's already supported for a long time. If the control flag V4L2_CTRL_FLAG_GRABBED > > is set, then the control is marked busy. > > > > There aren't many drivers that use this flag, but some do. > > The problem is it's a flag. In this case the driver marking the control busy > would be a different driver from the one that implements it, and I don't > think we could trust only one of the drivers will want to modify it. So it'd > have to be a counter instead. Why would another driver than the bridge driver want to change this? Right now it is no problem for the bridge driver to change the grabbed flag of a control of a subdev driver. If this would have to be implemented as a counter, then that would make things more complicated. But I'd like to see an actual need for that before I would consider implementing this. > That could still require special handling in some cases so we could specify > which controls may be grabbed by other drivers and when as the drivers may > want to modify the controls themselves, too. Well, if someone grabbed the control, then no driver or application should be able to modify it until it is 'ungrabbed'. Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
