Hi, On Fri, 2008-10-03 at 16:03 +0200, ext Hans Verkuil wrote: > Hi Vaibhav, > > Hmm, this is getting quite confusing for me :-) > > If I understand it correctly, TI posted two patches while I was on > vacation: one for the DSS library and one for the V4L2 driver. I > quickly looked at the DSS library patch, but I cannot really comment on > that one as it is very omap specific, so as far as I am concerned it is > pretty much up to TI to decide how to set this up. If I understand it > correctly the DSS 'library' basically provides v4l2/fb drivers with the > low-level platform functionality those drivers need. So I'm not sure > whether 'library' is really the right term here. 'DSS platform code' is > more appropriate. > > I definitely have questions regarding the V4L2 driver, but I'll reply to > that patch separately. > > I also understand that there is an alternative DSS implementation from > Tomi? But I can't seem to find any link to that code. A link to the > code would be appreciated. I've only sent it to linux-omap list for now. I'm planning to send it to fbdev-devel list sometime in the near future. Here are my mails: http://marc.info/?l=linux-omap&m=122114505030542&w=2 and http://marc.info/?l=linux-omap&m=122209502314197&w=2 The link to the implementation is a bit old, since then I've set up a public repo at http://www.bat.org/~tomba/git/linux-omap-dss.git/ But most of that code is also very omap specific =). > Regarding v4l2 vs fb: the normal way such things are implemented is that > the V4L2 API is used for video streaming while the FB API is used to > interface to displays and/or menu overlays. The FB API is a natural fit > for graphics applications like X and Qt, whereas the V4L2 API is meant > to handle video streaming in an efficient manner and with correct > timings. You can be creative and use a FB device to stream video or a > V4L2 device for graphics/overlay output, but you only make it hard on > yourself and the application writers. That has been my understanding. OMAP has three overlays (gfx, vid1, vid2) but I wouldn't want to dedicate vid1/2 overlays to V4L2 devices, because often you want to use them the same way as the gfx overlay, and framebuffer fits that better (for example, having a UI on the LCD and TV-out at the same time). So if and when I add V4L2 support, I'd like the choice between FB and V4L2 to be configurable per overlay. Perhaps just compile time configuration, but still. > Regards, > > Hans Tomi > On Friday 03 October 2008 14:47:23 Hiremath, Vaibhav wrote: > > Hi Tomi, > > > > Thanks, > > Vaibhav Hiremath > > Senior Software Engg. > > Platform Support Products > > Texas Instruments Inc > > Ph: +91-80-25099927 > > > > > -----Original Message----- > > > From: Tomi Valkeinen [mailto:tomi.valkeinen@xxxxxxxxx] > > > Sent: Thursday, October 02, 2008 1:55 PM > > > To: Hiremath, Vaibhav > > > Cc: Shah, Hardik; linux-omap@xxxxxxxxxxxxxxx; > > > video4linux-list@xxxxxxxxxx Subject: RE: [PREVIEW] New display > > > subsystem for OMAP2/3 > > > > > > Hi Vaibhav, > > > > > > On Wed, 2008-10-01 at 16:21 +0530, ext Hiremath, Vaibhav wrote: > > > > Tomi, > > > > > > > > Have you got a chance to review the DSS library and V4l2 driver > > > > which we have posted? > > > > > > Unfortunately not very much. I've been glancing the DSS side of the > > > driver, but not the v4l side as I don't know much about it. > > > > > > There seems to be awfully lot ifdefs for board/cpu types in the > > > code. > > > > As far as ifdefs are concerned, they are added to take care of > > OMAP2/3 variants. Especially you will find many instances of > > CONFIG_ARCH_OMAP3410 and the reason is obvious, OMAP3410 doesn't have > > VENC. As I have mentioned before, DSS library is designed to support > > both LCD, TV, and many more. > > > > > Also there are strange things defined, like L4_VIRT > > > > You are right; the code requires little-bit cleaning. There are some > > macros defined which driver or library doesn't use. We are in the > > process of cleaning and soon will be posting patches. > > > > > My biased and superficial view of the differences between my DSS > > > and yours is that: > > > > Tomi, here I differ from you. There should not be biased opinion. > > What we are looking here is a good design which will fulfill all our > > requirements/use case, like LCD, DVI, HDMI and TV for us and DSI, > > RFBI for you. > > > > > - My implementation is cleaner, better organized and more generic > > > > Again, here both of us will be having biased comments to support our > > own design, so I would prefer not to comment on this. Lets people on > > the community decide whose design is better. > > > > > - My implementation has support for DSI, SDI, RFBI, L4 updates > > > > DSI, SDI and RFBI are the modes, which we can add anytime to the > > system depending as per our requirement. It is again driven by use > > case; you have use cases for DSI, SDI and RFBI. We have for TV, DVI, > > HDMI and LCD, so we strongly concentrated on these. > > > > We can very well add these supports to DSS Library with minimal > > effort. > > > > > - Your implementation has better support for "extra" things like > > > VRFB, color conversions, alpha etc. > > > - Your implementation most likely has better power management > > > support. - And of course what is most visible to the user, my > > > version uses only framebuffers, and yours uses also v4l2 devices. > > > > You really can't deny the V4L2 framework advantages over framebuffer, > > especially for streaming kind of applications. Looking towards the > > hardware features OMAP supports; we would really require to have such > > support/capabilities. Community is also in agreement for the V4L2 > > interface on OMAP-DSS. > > > > Tony/Hans, > > Your comments would be helpful here. > > > > > As for the future, I have no choice but to keep using my DSS as we > > > need the features it has. I feel it would be quite a big job to get > > > those in to your driver. And even if I had a choice, I > > > (unsurprisingly =) think that my version is better and would stick > > > to it. > > > > It's your personal choice to stick to whichever code base you want, I > > don't want to comment on that. But what I believe is, with your > > design we are limiting ourselves from supporting most of the features > > which hardware provides. > > > > We can work together to add more support to DSS library. > > > > > Have you had time to look at my code after I changed the overlay > > > handling? I've put the most recent version to a public git tree at > > > http://www.bat.org/~tomba/git/linux-omap-dss.git/ and I'll try to > > > keep that up to date. > > > > Definitely I will review this code base, and will appreciate if I > > found something good. > > > > > Tomi > > > > > > > Thanks, > > > > Vaibhav Hiremath > > > > Senior Software Engg. > > > > Platform Support Products > > > > Texas Instruments Inc > > > > Ph: +91-80-25099927 > > > > > > > > > -----Original Message----- > > > > > From: Hiremath, Vaibhav > > > > > Sent: Monday, September 15, 2008 9:51 PM > > > > > To: 'Tomi Valkeinen' > > > > > Cc: Shah, Hardik; linux-omap@xxxxxxxxxxxxxxx; > > > > > video4linux-list@xxxxxxxxxx Subject: RE: [PREVIEW] New display > > > > > subsystem for OMAP2/3 > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > Vaibhav Hiremath > > > > > Senior Software Engg. > > > > > Platform Support Products > > > > > Texas Instruments Inc > > > > > Ph: +91-80-25099927 > > > > > TI IP Ph: 509-9927 > > > > > http://dbdwss01.india.ti.com/pspproducts/ > > > > > > > > > > > -----Original Message----- > > > > > > From: linux-omap-owner@xxxxxxxxxxxxxxx > > > > > > [mailto:linux-omap-owner@xxxxxxxxxxxxxxx] On Behalf Of > > > > > > Tomi > > > > > > > > > Valkeinen > > > > > > Sent: Monday, September 15, 2008 8:08 PM > > > > > > To: Hiremath, Vaibhav > > > > > > Cc: Shah, Hardik; linux-omap@xxxxxxxxxxxxxxx; > > > > > > video4linux-list@xxxxxxxxxx Subject: RE: [PREVIEW] New > > > > > > display subsystem for OMAP2/3 > > > > > > > > > > > > On Mon, 2008-09-15 at 19:02 +0530, ext Hiremath, Vaibhav > wrote: > > > > > > > We more concentrated on TV and LCD interface, out design > > > > > > > doesn't support DSI as of now. As > > > > > > > > > > > > mentioned earlier it is easily extendible to support DSI. > > > > > > > > > > > > > If I understand your implementation correctly, right now > > > > > > > there is no way you can switch the > > > > > > > > > > > > outputs, I mean to say from LCD to DVI. The frame buffer > > > > > > driver gets the handle with API omap_dss_get_display, which > > > > > > will return pointer to omap_display for panel-sdp3430. > > > > > > Henceforth > > > > > > all > > > > > > > > > your functions will use omap_display configuring for LCD > > > > > > panel. How are you planning to add > > > > > > support > > > > > > > > > for this? Through some ioctls or sysfs entry? How about > > > > > > switching between multiple overlay > > > > > > > > > > managers? > > > > > > > > > > > You can switch the outputs in the DSS driver. You can > > > > > > enable/disable displays individually, and configure the > > > > > > planes and or L4 pixel source for the display. > > > > > > > > > > > > But yes, the fb driver does not support that currently. > > > > > > > > > > > > One idea I had was to present each display with one > > > > > > framebuffer, so let's say we have 3 displays, we would have > > > > > > fb[0-2]. In addition to that, we would have two framebuffers > > > > > > for the video overlays. Only one of the displays can be > > > > > > updated with DISPC, so the overlays would appear there. > > > > > > > > > > > > Then the display that is updated with DISPC could be changed > > > > > > on the fly to another one, but the framebuffer arrangement > > > > > > would stay the same (so fb0 would still be seen on display0, > > > > > > even if it's now updated with L4). > > > > > > > > > > > > There's still the question how to manage the video overlays, > > > > > > in this scenario they would automatically move to other LCD's > > > > > > as the DISPC target is changed. Also the TV-out is > > > > > > problematic. > > > > > > > > > > > > > This issue has been addresses with our design, you can > > > > > > > change the output either to TV, LCD or > > > > > > to > > > > > > > > > DVI through sysfs entry. Switching between multiple overlay > > > > > > managers is very well supported in > > > > > > DSS > > > > > > > > > library. Currently SYSFS is the user interface layer to > > > > > > control the overlay managers. But in > > > > > > future > > > > > > > > > DSS library will easily be suitable to support media > > > > > > processor interface which is in concept > > > > > > phase > > > > > > > > > right now. RFC for the media processor is at > > > > > > > > > > > > Does your design support displays that are not updated with > > > > > > DISPC? > > > > > > > > > > Yes, it should. I don't see any reason why it should fail if > > > > > the display is completely > > > > > > independent. > > > > > > > > > Your design has good points. I have to think about the > > > > > > overlay managers a bit more. Especially if in some future > > > > > > hardware there were more overlay managers instead of the > > > > > > current two. > > > > > > > > > > Let me take this opportunity, shortly I will post the DSS > > > > > library and V4L2 driver. We can work together to add support > > > > > for DSI, RFBI and SDI support to it. > > > > > > > > > > > > http://lists-archives.org/video4linux/23652-rfc-add-support > > > > > > >-to-query-and-change-connections- > > > > > > > > > > inside- > > > > > > > > > > > a-media-device.html > > > > > > > > > > > > > > I also wanted to be able to change the configuration on > > > > > > > > the fly, changing where DISPC output is going and which > > > > > > > > displays are updated with CPU or sDMA. > > > > > > > > > > > > > > > > This is why I have the display-concept in my design. > > > > > > > > > > > > > > Here we both are on same page, you have broken the displays > > > > > > > and modes supported into multiple > > > > > > > > > > files > > > > > > > > > > > registering functions to the display.c file, there are many > > > > > > loopholes though. > > > > > > > > > > > > > > I haven't made support for multiple users of the displays > > > > > > > > (like separate fb and v4l drivers), but I don't > > > > > > > > immediately see why it couldn't be done. > > > > > > > > > > > > > > How are you going to handle the concurrency between these > > > > > > > two? > > > > > > > > > > > > In the simple case of just an LCD and a TV-out, what are the > > > > > > concurrency problems? Each plane is independent of each > > > > > > other. Sure you need to check that the output is on if > > > > > > there's a plane enabled there and basic things like that. Are > > > > > > there some other issues I'm not seeing? > > > > > > > > > > Yes some of the features of the DSS are tied to overlay > > > > > managers and not the individual planes > > > > > > like > > > > > > > > global alpha, alpha blending enabling and timing parameters. So > > > > > while programming of these > > > > > > parameters > > > > > > > > DSS library will have to maintain the data structures for the > > > > > same and then any high level > > > > > > drivers > > > > > > > > can query those data structures. > > > > > > > > > > > > > However, there are some questions regarding that, as the > > > > > > > > planes do not represent displays, but just overlay > > > > > > > > planes. What happens when both fb and v4l drivers want to > > > > > > > > change the resolution or timings of the display? > > > > > > > > > > > > > > > > Also I still don't quite know how to present displays to > > > > > > > > user space. Currently my omapfb just uses the first > > > > > > > > display, and that's it. I think in the end the user (be > > > > > > > > it X server, or perhaps some entity over it), needs to > > > > > > > > have some understanding of what OMAP offers and how it > > > > > > > > can use the displays. And there probably needs to be some > > > > > > > > product spesific configuration regarding this in > > > > > > > > userspace. > > > > > > > > > > > > > > Here are you saying application will have hardware specific > > > > > > > support? Is this feasible? > > > > > > > > > > > > I don't see any other way. The displays are not independent > > > > > > of each other. For example the OMAP3 SDP has LCD and DVI > > > > > > outputs. They can't be switched programmatically, but let's > > > > > > say it was possible. Only one of those displays can be > > > > > > enabled at time. If an application wants to use them both, it > > > > > > has to understand that they will not both work at the same > > > > > > time. > > > > > > > > > > > > Or if there are two DSI displays, and one is updated with > > > > > > DISPC and the other via L4. The application has to know that > > > > > > a video overlay can only be used on the first display, or it > > > > > > has to exchange the DISPC/L4 updating order. > > > > > > > > > > > > Of course this is product specific software and > > > > > > configuration, not something I'm planning to put in the > > > > > > driver. A normal application does not have to know anything > > > > > > about it. I was just bringing it up to demonstrate what must > > > > > > be possible. > > > > > > > > > > > > Tomi > > > > > > > > > > > > > > > > > > -- > > > > > > To unsubscribe from this list: send the line "unsubscribe > > > > > > linux-omap" in the body of a message to > > > > > > majordomo@xxxxxxxxxxxxxxx > > > > > > More majordomo info at > > > > > > http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
