> -----Original Message----- > From: linux-media-ow...@vger.kernel.org [mailto:linux-media- > ow...@vger.kernel.org] On Behalf Of Hans Verkuil > Sent: Friday, September 11, 2009 11:51 AM > To: Karicheri, Muralidharan > Cc: Patrick Boettcher; Linux Media Mailing List > Subject: Re: RFCv2: Media controller proposal > > On Friday 11 September 2009 01:08:30 Karicheri, Muralidharan wrote: > > > > Hans, > > > > Thanks for your reply.. > > >> > > >> <snip>
> > > > Right. That case (2 above) is easily taken care by v4l2 device > driver. We used FBDev driver to drive OSD Layer because that way > VPBE can be used by user space applications like x-windows? What is > the alternative for this? > > Is there a example v4l2 device using OSD like hardware and running > x-windows or other traditional graphics application? I am not aware > of any and the solution seems to be the right one here. > > > > So the solution we used (case 3)involves FBDev to drive the OSD > layers and V4L2 to drive the video layer. > > As usual, ivtv is doing all that. The ivtv driver is the main > controller of > the hardware. The ivtvfb driver provides the FB API towards the OSD. > The > X driver for the OSD is available here: > > http://dl.ivtvdriver.org/xf86-video-ivtv/archive/1.0.x/xf86-video- > ivtv-1.0.2.tar.gz > > This is the way to handle it. > > > > > > > > >This is very similar to the ivtv and ivtvfb drivers: if the > framebuffer is > > >in > > >use, then you cannot change the output standard (you'll get an > EBUSY error) > > >through a video device node. > > > > > > > Does the ivtvfb and ivtv works with the same set of v4l2 sub > devices for output? In our case, VPBE can work with any sub device > that can accept a BT.656/BT1120/RGB bus interface. So the FBDev > device and V4L2 device( either as standalone device or as co- > existent device) should work with the same set of sub devices. So > the question is, how both these bridge device can work on the same > sub device? If both can work with the same sub device, then what you > say is true and can be handled. That is the reason we used the > sysfs/Encoder manager as explained in my earlier email. > > Look at ivtvfb.c (it's in media/video/ivtv). The ivtvfb_init > function will just [Hiremath, Vaibhav] I think our mail crossed each other. Interesting, and is something new for me. Let me understand the implementation here first then I can provide some comments on this. Thanks, Vaibhav > find any ivtv driver instances and register itself with them. Most > of the > hard work is actually done by ivtv and ivtvfb is just the front-end > that > implements the FB API. The video and OSD hardware is usually if not > always > so intertwined that it should be controlled by one driver, not two. > > This way ivtv keeps full control over the sub-devices as well and > all output > changes will go to the same encoder, regardless of whether they > originated > from the fb or a video device node. > > > > > >That's exactly what you would expect. If the framebuffer isn't > used, then > > >you > > >can just use the normal V4L2 API to change the output standard. > > > > > >In practice, I think that you can only change the resolution in > the FB API. > > >Not things like the framerate, let alone precise pixelclock, > porch and sync > > >widths. > > > > > > There are 3 use cases > > > > 1) Pure FBDev device driving graphics to VPBE OSD layers -> sub > devices -> Display (LCD/TV) > > > > This would require FBDev loading a required v4l2 the sub > device (Not sure if FBDev community like this approach) and using it > to drive the output. We will not be able to change the output. But > output resolutions and timing can be controlled through fbset > command which allow you to change pixel clock, porch, sync etc. > > Bad idea. The fb API and framework is not really able to deal with > the > complexity of combined video and OSD devices. The v4l2 framework can > (esp. > when we have a media controller). > > > 2)Pure V4L2 device driving video to VPBE video layers -> sub > devices > > ->Display (LCD/TV) > > - No issues here > > > > 3)v4l2 and FBDev nodes co-exists. V4l2 drives video and FBDev > drives OSD layers and the combined out ->VPBE ->sub devices -> > Display (LCD/TV) > > - Not sure which bridge device should load up and manage the > sub devices. If V4l2 manages the sub devices, how FBDev driver can > set the timings in the current sub device since it has no knowledge > of the v4l2 device and the sub device it owns/manages. > > You should not attempt to artificially separate the two. You can't > since both > v4l and fb share the same hardware. You need one v4l driver that > will take > care of both and the FB driver just delegates the core OSD low-level > work to > the v4l driver. > > > > > > > > >Much better to let the two cooperate: you can use both APIs, but > you can't > > >change the resolution in the fb if streaming is going on, and you > can't > > >change the output standard of a video device node if that changes > the > > >resolution while the framebuffer is in used. > > That is what I mean by use case 3). We can live with the > restriction. But sub device model currently is v4l2 specific and I > am not sure if there is a way same sub device can be accessed by > both bridge devices. Any help here is appreciated. > > > > > > > >No need for additional sysfs entries. > > > > > > > If we can use sub devices framework, we wouldn't need sysfs > > > > >> > > >> There is an encoder manager to which all available encoders > registers > > >(using internally developed interface) and based on commands > received at > > >Fbdev/sysfs interfaces, the current encoder is selected by the > encoder > > >manager and current standard is selected. The encoder manager > provides API > > >to retrieve current timing information from the current encoder. > FBDev and > > >V4L2 drivers uses this API to configure OSD/video layers for > streaming. > > >> > > >> As you can see, controlling output/mode is a common function > required for > > >both v4l2 and FBDev devices. > > >> > > >> One way to do this to modify the encoder manager such that it > load up the > > >encoder sub devices. This will allow our customers to migrate to > this > > >driver on GIT kernel with minimum effort. If v4l2 display bridge > driver > > >load up the sub devices, it will make FBDev driver useless unless > media > > >controller has some way to handle this scenario. Any idea if > media > > >controller RFC address this? I will go over the RFC in details, > but if you > > >have a ready answer, let me know. > > > > > >I don't think this has anything to do with the media controller. > It sounds > > >more like a driver design issue to me. > > > > > Not really :( > > > > When we talk about media controller, it should allow multiple > > streaming nodes to work with the same output or multiple outputs > right? Here an entity can have FB device and V4L2 device nodes and > both should be able > > to stream onto the same output managed by a sub device. > > > > /dev/fb0 --> VPBE-OSD0 ->|-> VPBE ->analog output > (NTSC/PAL/1080i/720P) > > /dev/fb2 --> VPBE-OSD1 ->| ->digital LCD port > > | - > >BT.656/BT.1120/VGA/VISA-> > > | -> encoders > > /dev/video2 --> VPBE-VID0 ->| > > /dev/video3 --> VPBE-VID1 ->| > > > > Current sub device frame work doesn't seems to work with this > configuration. > > Or Am I missing something? Is there an example of this > implementation in ivtv or other platforms? > > It's no problem as long as the v4l driver remains in control of both > the > video and OSD. > > Regards, > > Hans > > > > > Murali > > >Regards, > > > > > > Hans > > > > > >-- > > >Hans Verkuil - video4linux developer - sponsored by TANDBERG > Telecom > > > > -- > > 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 > > > > > > -- > Hans Verkuil - video4linux developer - sponsored by TANDBERG Telecom > -- > 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 -- 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
