[lkml]   [2009]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: Vramfs: filesystem driver to utilize extra RAM on VGA devices
Every VGA device connected to the PCI bus has resources that are known 
to the Linux kernel. One of the memory resources is the video RAM
(always the largest prefetchable resource listed), with the base and
length known to the PCI subsystem. So, all vramfs needs on mount is the
PCI device, and the mountpoint, and it can dole it out to userspace.
Reading and writing is handled with ioremap(). mmap() is handled by
directly mmaping() that VRAM into user-space (just like /dev/fb0). Files
are recorded in system memory as a list of entities with a starting
block and length, so no fragmentation is possible.

No communication with the GPU is needed to do this, it's possible to use
VRAM this way even on devices that nobody in the system knows how to
talk to.
> How do you accomplish that?
> (I haven't yet looked at your code...)
> -PWM

 \ /
  Last update: 2009-01-29 18:33    [W:0.063 / U:1.260 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site