0001 .. SPDX-License-Identifier: GPL-2.0
0002
0003 The VPBE V4L2 driver design
0004 ===========================
0005
0006 Functional partitioning
0007 -----------------------
0008
0009 Consists of the following:
0010
0011 1. V4L2 display driver
0012
0013 Implements creation of video2 and video3 device nodes and
0014 provides v4l2 device interface to manage VID0 and VID1 layers.
0015
0016 2. Display controller
0017
0018 Loads up VENC, OSD and external encoders such as ths8200. It provides
0019 a set of API calls to V4L2 drivers to set the output/standards
0020 in the VENC or external sub devices. It also provides
0021 a device object to access the services from OSD subdevice
0022 using sub device ops. The connection of external encoders to VENC LCD
0023 controller port is done at init time based on default output and standard
0024 selection or at run time when application change the output through
0025 V4L2 IOCTLs.
0026
0027 When connected to an external encoder, vpbe controller is also responsible
0028 for setting up the interface between VENC and external encoders based on
0029 board specific settings (specified in board-xxx-evm.c). This allows
0030 interfacing external encoders such as ths8200. The setup_if_config()
0031 is implemented for this as well as configure_venc() (part of the next patch)
0032 API to set timings in VENC for a specific display resolution. As of this
0033 patch series, the interconnection and enabling and setting of the external
0034 encoders is not present, and would be a part of the next patch series.
0035
0036 3. VENC subdevice module
0037
0038 Responsible for setting outputs provided through internal DACs and also
0039 setting timings at LCD controller port when external encoders are connected
0040 at the port or LCD panel timings required. When external encoder/LCD panel
0041 is connected, the timings for a specific standard/preset is retrieved from
0042 the board specific table and the values are used to set the timings in
0043 venc using non-standard timing mode.
0044
0045 Support LCD Panel displays using the VENC. For example to support a Logic
0046 PD display, it requires setting up the LCD controller port with a set of
0047 timings for the resolution supported and setting the dot clock. So we could
0048 add the available outputs as a board specific entry (i.e add the "LogicPD"
0049 output name to board-xxx-evm.c). A table of timings for various LCDs
0050 supported can be maintained in the board specific setup file to support
0051 various LCD displays.As of this patch a basic driver is present, and this
0052 support for external encoders and displays forms a part of the next
0053 patch series.
0054
0055 4. OSD module
0056
0057 OSD module implements all OSD layer management and hardware specific
0058 features. The VPBE module interacts with the OSD for enabling and
0059 disabling appropriate features of the OSD.
0060
0061 Current status
0062 --------------
0063
0064 A fully functional working version of the V4L2 driver is available. This
0065 driver has been tested with NTSC and PAL standards and buffer streaming.
