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kernel/linux-imx6_3.14.28/Documentation/video4linux/README.davinci-vpbe 3.93 KB
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                  VPBE V4L2 driver design
   ======================================================================
  
   File partitioning
   -----------------
   V4L2 display device driver
           drivers/media/platform/davinci/vpbe_display.c
           drivers/media/platform/davinci/vpbe_display.h
  
   VPBE display controller
           drivers/media/platform/davinci/vpbe.c
           drivers/media/platform/davinci/vpbe.h
  
   VPBE venc sub device driver
           drivers/media/platform/davinci/vpbe_venc.c
           drivers/media/platform/davinci/vpbe_venc.h
           drivers/media/platform/davinci/vpbe_venc_regs.h
  
   VPBE osd driver
           drivers/media/platform/davinci/vpbe_osd.c
           drivers/media/platform/davinci/vpbe_osd.h
           drivers/media/platform/davinci/vpbe_osd_regs.h
  
   Functional partitioning
   -----------------------
  
   Consists of the following (in the same order as the list under file
   partitioning):-
  
   1. V4L2 display driver
      Implements creation of video2 and video3 device nodes and
      provides v4l2 device interface to manage VID0 and VID1 layers.
  
   2. Display controller
      Loads up VENC, OSD and external encoders such as ths8200. It provides
      a set of API calls to V4L2 drivers to set the output/standards
      in the VENC or external sub devices. It also provides
      a device object to access the services from OSD subdevice
      using sub device ops. The connection of external encoders to VENC LCD
      controller port is done at init time based on default output and standard
      selection or at run time when application change the output through
      V4L2 IOCTLs.
  
      When connected to an external encoder, vpbe controller is also responsible
      for setting up the interface between VENC and external encoders based on
      board specific settings (specified in board-xxx-evm.c). This allows
      interfacing external encoders such as ths8200. The setup_if_config()
      is implemented for this as well as configure_venc() (part of the next patch)
      API to set timings in VENC for a specific display resolution. As of this
      patch series, the interconnection and enabling and setting of the external
      encoders is not present, and would be a part of the next patch series.
  
   3. VENC subdevice module
      Responsible for setting outputs provided through internal DACs and also
      setting timings at LCD controller port when external encoders are connected
      at the port or LCD panel timings required. When external encoder/LCD panel
      is connected, the timings for a specific standard/preset is retrieved from
      the board specific table and the values are used to set the timings in
      venc using non-standard timing mode.
  
      Support LCD Panel displays using the VENC. For example to support a Logic
      PD display, it requires setting up the LCD controller port with a set of
      timings for the resolution supported and setting the dot clock. So we could
      add the available outputs as a board specific entry (i.e add the "LogicPD"
      output name to board-xxx-evm.c). A table of timings for various LCDs
      supported can be maintained in the board specific setup file to support
      various LCD displays.As of this patch a basic driver is present, and this
      support for external encoders and displays forms a part of the next
      patch series.
  
   4. OSD module
      OSD module implements all OSD layer management and hardware specific
      features. The VPBE module interacts with the OSD for enabling and
      disabling appropriate features of the OSD.
  
   Current status:-
  
   A fully functional working version of the V4L2 driver is available. This
   driver has been tested with NTSC and PAL standards and buffer streaming.
  
   Following are TBDs.
  
   vpbe display controller
      - Add support for external encoders.
      - add support for selecting external encoder as default at probe time.
  
   vpbe venc sub device
      - add timings for supporting ths8200
      - add support for LogicPD LCD.
  
   FB drivers
      - Add support for fbdev drivers.- Ready and part of subsequent patches.