RFC- High level design for pushing the V4L2 driver based on TI Soc. Hardware Background ====================== DSS (Display Sub System) IP on the OMAP3 SoC of TI provides a logic to display a video frame from the memory frame buffer on a liquid crystal display (LCD) panel or a TV set. It includes two video pipelines and one graphic pipeline. It also includes two overlay managers for compositing the pictures from different pipelines. Below is the high level block diagram of the DSS IP and its capabilities on OMAP3 video1 pipeline --|-----------compositor 0--|---TV encoder|-------S Video, composite outputs video2 pipeline --| graphic pipeline --|-----------compositor 1--|---LCD Note: Output of all the pipelines can go to any of the compositors. High level design of the OMAP3 SoC can be found at http://focus.ti.com/general/docs/wtbu/wtbuproductcontent.tsp?templateId=6123&navigationId=12643&contentId=14649 Frame buffer driver is already there on the GIT controlling the graphic pipeline. This is the initial proposal to push the V4L2 display driver onto GIT for controlling the video pipelines. This will be done in different phases. Proposal ============================================================================ As shown in the block diagram compositor number 0 connected to TV will be controlled by the V4L2 driver and compositor number 1 connected to LCD will be controlled by FBDEV driver. FBDEV driver implementation controlling the graphics pipeline is already there on GIT tree. V4L2 driver controlling the video pipelines needs to be pushed. Below is the software implementation block diagram for the above hardware block diagram. /dev/video0--|video1 pipeline--|-----------compositor 0--|---TV encoder /dev/video1--|video2 pipeline--| Below implementation is already there on GIT tree. /dev/fb0--|graphics pipeline--|-----------compositor 1--|---LCD As there is a single compositor between both the video pipelines there will be some coherency issues like changing the standard on one pipeline will affect the standard on other one. omap2_dss.c functional layer will maintain the coherency between two pipelines for the common hardware like compositor. Future enhancement is targeted to use both FBDEV and V4L2 drivers using both the compositors and all the functional level code is in omap2_dss.c and omap2_venc.c file, so we want omap2_dss.c and omap2_venc.c files to be placed in architecture directory (arch/arm/plat-omap/). Future enhancements will also cover all the existing functionality provided by FBDEV driver like RFBI etc. Since both the driver frame work is different and compositors will be shared by both (FBDEV and V4L2 drivers) in future enhancements. There should be some way of central entity for controlling the compositors. Comments are welcomed on this design issue. High Level Design. =================== Following are the files consisting the TI V4L2 driver. /arch/arm/plat-omap/omap2_dss.c =============================== This is a functional layer for the DSS hardware. It mainly has functions like configuring the video pipelines, starting the streaming on video pipelines, setting the color conversion etc. /arch/arm/plat-omap/omap2_venc.c ================================= It is a functional layer for the video encoder. In DSS the encoder is inside the IP. This file mainly deals with configuration of the encoder registers according to the TV standard selected. For on-board encoders (off-chip) encoder specific file will be in board directory. /drivers/media/video/omap/omap2_display.c ========================================== This is a core V4L2 driver file. It registers two video pipelines with the V4L2 frame work. It also implements the necessary ioctls supported by the V4L2. It also implements some of the custom ioctls not supported by V4L2 framework but hardware supports it. /drivers/media/video/omap/omap2_lib.c ======================================= This is a library file for the V4L2 driver. DSS provides some of the functionalities like cropping, window size and window position. This library file helps in setting all the parameters depending upon the crop window and display window selected. DSS also supports on the fly scaling so it also calculates the vertical and horizontal scaling factor depending upon the display and crop window selected. Thanks and Regards, Hardik Shah -- 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
