Hi Marek, On Wednesday, March 30, 2011 4:01 PM Marek Szyprowski wrote: > Hello, > > On V4L2 brainstorming meeting in Warsaw we discussed the need of a > framebuffer userspace interface for video output devices. Such > framebuffer interface is aimed mainly for legacy applications and/or > interoperatibility with Xfbdev. > > I proposed to give the idea of generic fb-on-top-of-video-node a second > try, now using the power of videobuf2. > > This short patch series demonstrates that this approach is possible. We > succesfully implemented a framebuffer emulator and tested it with > s5p-hdmi driver on Samsung Exynos4 platform. > > This initial version provides a basic non-accelerated framebuffer > device. The emulation is started on the first open of the framebuffer > device and stopped on last close. The framebuffer boots in 'blanked' > mode, so one also needs to make a call to blank ioctl (with > FB_BLANK_UNBLANK argument) to enable video output. > > We successfully managed to get vanilla Xfbdev server working on top of > it without ANY changes in X server sources. > > The framebuffer resolution and pixel format is autoconfigured from the > parameters of the corresponding video output node. One can use v4l2-ctrl > (or similar) tool to select pixel format, resolution, output, etc (and > in the near future also the composition on the target video device). > > There a few requirements for the video output driver: > 1. support for single-buffering mode > 2. support for videoc_ioctl interface (this might change in the future) > 3. use memory allocator that allows coherent mappings (mmaped framebuffer > will be accessed by application while it is displayed by dma engine). > > The changes that are needed in the video output driver are really > simple. Mainly one need to add just a call to vb2_fb_register(q, vfd) > and vb2_fb_register(fb) functions. > > The future versions might aslo include the following features: > - vsync event translation into WAIT_VSYNC framebuffer ioctl > - support for frame buffer panning with upcoming S_COMPOSE ioctl > As I know, the panning is different from upcoming S_COMPOSE. The panning selects the frame buffer area which will be read by display controller to support virtual screen feature. But as I remember, the S_COMPOSE is related in positioning on the display device like HDMI. IMO, VIDIOC_S_EXTCROP makes sense for panning. > The patch series is based on the V2 of the s5p-hdmi driver. The complete > kernel tree will be available on: > git://git.infradead.org/users/kmpark/linux-2.6-samsung vb2-fb-tv branch. > > An updated s5p-hdmi/tv driver will be posted soon. > > Best regards > -- > Marek Szyprowski > Samsung Poland R&D Center > > > Complete patch summary: > > Marek Szyprowski (2): > media: vb2: add frame buffer emulator for video output devices > media: s5p-hdmi: add support for frame buffer emulator > > drivers/media/video/Kconfig | 7 + > drivers/media/video/Makefile | 1 + > drivers/media/video/s5p-tv/Kconfig | 1 + > drivers/media/video/s5p-tv/mixer.h | 2 + > drivers/media/video/s5p-tv/mixer_video.c | 10 + > drivers/media/video/videobuf2-fb.c | 565 ++++++++++++++++++++++++++++++ > include/media/videobuf2-fb.h | 22 ++ > 7 files changed, 608 insertions(+), 0 deletions(-) > create mode 100644 drivers/media/video/videobuf2-fb.c > create mode 100644 include/media/videobuf2-fb.h > > -- > 1.7.1.569.g6f426 > -- > 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 -- 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
