| .. 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. |
