reading pixel data from kernelspace

reading pixel data from kernelspace

[Nathan King]

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Hey folks,

I'm messing with some virtual framebuffering, and had a question. When in
userspace, if I want to read the contents of the framebuffer I just do a

open("/dev/fb0",O_RDONLY)

and I've got a nice clean capture of the screen. Where, however, does this
data live in kernelspace? My vfb driver declares a pointer and then
allocates whatever memory the display needs, basically
width*height*bytes_per_pixel bytes. A lot like the variable "videomemory" in
drivers/video/vfb.c.  If I try to copy this data, however, it comes out
garbled. Some parts look a little like the original, but most of it is
pretty random. Is there another home for this pixel data somewhere? I tried
reading from info->screen_base, but got exactly the same results.

Much thanks,
Nathan

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