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The VPBE V4L2 driver design
File partitioning
V4L2 display device driver
VPBE display controller
VPBE venc sub device driver
VPBE osd driver
Functional partitioning
Consists of the following (in the same order as the list under file
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
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.
To be done
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.