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-The U-Boot Driver Model Project
-===============================
-Video output analysis
-=====================
-Marek Vasut <marek.vasut@gmail.com>
-2012-02-20
-
-I) Overview
------------
-
-The video drivers are most often registered with video subsystem. This subsystem
-often expects to be allowed access to framebuffer of certain parameters. This
-subsystem also provides calls for STDIO subsystem to allow it to output
-characters on the screen. For this part, see [ UDM-stdio.txt ].
-
-Therefore the API has two parts, the video driver part and the part where the
-video driver core registers with STDIO API.
-
-The video driver part will follow the current cfb_console approach, though
-allowing it to be more dynamic.
-
-II) Approach
-------------
-
-Registering the video driver into the video driver core is done by calling the
-following function from the driver probe() function:
-
- video_device_register(struct instance *i, GraphicDevice *gd);
-
-Because the video driver core is in charge or rendering characters as well as
-bitmaps on the screen, it will in turn call stdio_device_register(i, so), where
-"i" is the same instance as the video driver's one. But "so" will be special
-static struct stdio_device_ops handling the character output.
-
-
-III) Analysis of in-tree drivers
---------------------------------
-
- arch/powerpc/cpu/mpc8xx/video.c
- -------------------------------
- This driver copies the cfb_console [ see drivers/video/cfb_console.c ]
- approach and acts only as a STDIO device. Therefore there are currently two
- possible approaches, first being the conversion of this driver to usual STDIO
- device and second, long-term one, being conversion of this driver to video
- driver that provides console.
-
- arch/x86/lib/video.c
- --------------------
- This driver registers two separate STDIO devices and should be therefore
- converted as such.
-
- board/bf527-ezkit/video.c
- -------------------------
- This driver seems bogus as it behaves as STDIO device, but provides no input
- or output capabilities. It relies on DEV_EXT_VIDEO, which is no longer in use
- or present otherwise than as a dead code/define.
-
- board/bf533-stamp/video.c
- -------------------------
- This driver seems bogus as it behaves as STDIO device, but provides no input
- or output capabilities. It relies on DEV_EXT_VIDEO, which is no longer in use
- or present otherwise than as a dead code/define.
-
- board/bf548-ezkit/video.c
- -------------------------
- This driver seems bogus as it behaves as STDIO device, but provides no input
- or output capabilities. It relies on DEV_EXT_VIDEO, which is no longer in use
- or present otherwise than as a dead code/define.
-
- board/cm-bf548/video.c
- ----------------------
- This driver seems bogus as it behaves as STDIO device, but provides no input
- or output capabilities. It relies on DEV_EXT_VIDEO, which is no longer in use
- or present otherwise than as a dead code/define.