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+.. SPDX-License-Identifier: GPL-2.0
+
+The VPBE V4L2 driver design
+===========================
+
+Functional partitioning
+-----------------------
+
+Consists of the following:
+
+ 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.