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authorMichal Januszewski <spock@gentoo.org>2007-10-16 01:28:26 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-16 09:43:13 -0700
commit8bdb3a2d7df48b861972c4bfb58490853a228f51 (patch)
treefebc4fbe0fd90e4677fe7703350ce349ddbfc342 /Documentation/fb
parentcc54f46e39dff9891dd334ef158a238ff5a9ffd2 (diff)
uvesafb: the driver core
uvesafb is an enhanced version of vesafb. It uses a userspace helper (v86d) to execute calls to the x86 Video BIOS functions. The driver is not limited to any specific arch and whether it works on a given arch or not depends on that arch being supported by the userspace daemon. It has been tested on x86_32 and x86_64. A single BIOS call is represented by an instance of the uvesafb_ktask structure. This structure contains a buffer, a completion struct and a uvesafb_task substructure, containing the values of the x86 registers, a flags field and a field indicating the length of the buffer. Whenever a BIOS call is made in the driver, uvesafb_exec() builds a message using the uvesafb_task substructure and the contents of the buffer. This message is then assigned a random ack number and sent to the userspace daemon using the connector interface. The message's sequence number is used as an index for the uvfb_tasks array, which provides a mapping from the messages coming from userspace to the in-kernel uvesafb_ktask structs. The userspace daemon performs the requested operation and sends a reply in the form of a uvesafb_task struct and, optionally, a buffer. The seq and ack numbers in the reply should be exactly the same as those in the request. Each message from userspace is processed by uvesafb_cn_callback() and after passing a few sanity checks leads to the completion of a BIOS call request. Signed-off-by: Michal Januszewski <spock@gentoo.org> Signed-off-by: Antonino Daplas <adaplas@gmail.com> Cc: Paul Mundt <lethal@linux-sh.org> Cc: Paulo Marques <pmarques@grupopie.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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