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>

drivers/video/Kconfig

@@ -592,6 +592,24 @@ config FB_TGA
 
 	  Say Y if you have one of those.
 
+config FB_UVESA
+	tristate "Userspace VESA VGA graphics support"
+	depends on FB && CONNECTOR
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select FB_MODE_HELPERS
+	help
+	  This is the frame buffer driver for generic VBE 2.0 compliant
+	  graphic cards. It can also take advantage of VBE 3.0 features,
+	  such as refresh rate adjustment.
+
+	  This driver generally provides more features than vesafb but
+	  requires a userspace helper application called 'v86d'. See
+	  <file:Documentation/fb/uvesafb.txt> for more information.
+
+	  If unsure, say N.
+
 config FB_VESA
 	bool "VESA VGA graphics support"
 	depends on (FB = y) && X86

drivers/video/Makefile

@@ -115,6 +115,7 @@ obj-$(CONFIG_FB_XILINX)           += xilinxfb.o
 obj-$(CONFIG_FB_OMAP)             += omap/
 
 # Platform or fallback drivers go here
+obj-$(CONFIG_FB_UVESA)            += uvesafb.o
 obj-$(CONFIG_FB_VESA)             += vesafb.o
 obj-$(CONFIG_FB_IMAC)             += imacfb.o
 obj-$(CONFIG_FB_VGA16)            += vga16fb.o