VAR-SOM-OM35/7 Linux Display Driver
OMAP3 / DM37 / AM37 cpus Display Sub-System hardware integrates one graphics pipeline, two video pipelines, and two overlay managers (one for digital and one for analog interface). Digital interface is used for LCD and DVI output and analog interface is used for TV out.
The primary functionality of the display driver is to provide interfaces to user level applications and management of Display Sub-System hardware.
This section defines and describes the usage of user level interfaces of Video Display Driver.
Screen rotation, Video modes
FBDEV driver supports set of command line argument for enabling/setting rotation angle, enable/disable VRFB rotation, default mode, size of vram and debug option. These command line arguments can only be used with boot time arguments as FBDEV driver only supports static build.
Below is the list of arguments which Fbdev driver supports -
| Argument | Description |
|---|---|
| mode | Default video mode for specified displays |
| vram | VRAM allocated memory for a framebuffer, user can individually configure VRAM buffers for each plane/device node |
| vrfb | Use VRFB rotation for framebuffer |
| rotate | Default rotation applied to framebuffer |
| test | Draw test pattern to framebuffer whenever framebuffer settings change |
| debug | Enable debug messaging |
Following example shows how to specify 90 degree rotation in boot time argument:
# setenv bootargs_fs 'mem=80M@0x80000000 mem=128M@0x88000000 console=ttyS2,115200n8 noinitrd root=/dev/mtdblock4 rw rootfstype=jffs2 ethaddr=$(ethaddr) ip=dhcp omapfb.rotate=1 omapfb.vrfb=y
Following example shows how to specify size of framebuffer in boot time argument:
setenv bootargs_fs 'mem=80M@0x80000000 mem=128M@0x88000000 console=ttyS2,115200n8 noinitrd root=/dev/mtdblock4 rw rootfstype=jffs2 ethaddr=$(ethaddr) ip=dhcp vram=20M omapfb.vram=0:20M
Following example shows how to specify mode for framebuffer in boot time argument, the examples shows how to configure DVI mode to 1280x720 resolution @ 60hz.
This command doesn't change the default display to DVI, it only configures the DVI mode. To chagne the default display to DVI, refer to the DSS library section.
# setenv bootargs_fs 'mem=80M@0x80000000 mem=128M@0x88000000 console=ttyS2,115200n8 noinitrd root=/dev/mtdblock4 rw rootfstype=jffs2 ethaddr=$(ethaddr) ip=dhcp omapfb.mode=dvi:1280x720-24@60
Default display device settings
There are few arguments which allows control over core DSS functionality.
| Argument | Description |
|---|---|
| def_disp | Name of default display, to which all overlays will be connected |
| debug | Enable debug messages |
Following example shows how to specify default display to particular output in boot time argument:
# setenv bootargs_fs 'mem=80M@0x80000000 mem=128M@0x88000000 console=ttyS2,115200n8 noinitrd root=/dev/mtdblock4 rw rootfstype=jffs2 ethaddr=$(ethaddr) ip=dhcp omapfb.mode=dvi:1280x720-24@60 omapdss.def_disp="dvi"