new file mode 100644
@@ -0,0 +1,100 @@
+
+ VPBE V4L2 driver design
+ ======================================================================
+
+ File partitioning
+ -----------------
+ V4L2 display device driver
+ drivers/media/video/davinci/vpbe_display.c
+ drivers/media/video/davinci/vpbe_display.h
+
+ VPBE display controller
+ drivers/media/video/davinci/vpbe.c
+ drivers/media/video/davinci/vpbe.h
+
+ VPBE venc sub device driver
+ drivers/media/video/davinci/vpbe_venc.c
+ drivers/media/video/davinci/vpbe_venc.h
+ drivers/media/video/davinci/vpbe_venc_regs.h
+
+ VPBE osd driver
+ drivers/media/video/davinci/vpbe_osd.c
+ drivers/media/video/davinci/vpbe_osd.h
+ drivers/media/video/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 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 sub device
+ 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 connetected 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 ans setting of the external
+ encoders is not present, and would be a part of the next patch series.
+
+ 3. Venc subdevice
+ 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.
+
+ 4. osd subdevice
+ Osd subdevice implements all osd layer management and hardware specific
+ features. In the legacfy drivers (LSPxxx), the hardware specific features
+ are configured through proprietary IOCTLs at the fb device interface. Since
+ subdevices are going to support device nodes, application will be able
+ to configure the hardware feature directly by opening the osd subdevice
+ node and by calling the related IOCTL. So these proprietary IOCTLs are
+ to be removed from the FB Device driver when doing up port of these drivers to
+ mainline kernel. The V4L2 and FB device nodes supports only IOCTLS as per
+ the associated spec. The rest of the IOCTLs are to be moved to osd and
+ venc subdevices.
+
+ Current status:-
+
+ A build tested version of vpbe controller is available.
+
+ Following are TBDs.
+
+ vpbe display controller
+ - review and modify the handling of 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.
+
+ v4l2 driver
+ - A version is already developed which is to be cleaned up and unit tested
+
+ FB drivers
+ - Add support for fbdev drivers.- Ready and part of subsequent patches.