Large framebuffers and HIGHMEM systems
flat view
From: Jon Smirl <hidden>
Date: 2003-09-09 21:28:28
Fbdev needs to come up with a general solution for mapping large framebuffers on systems with over 1GB memory. For example my system does not have 64MB of free address space below 1GB, this causes my framebuffer drivers to fail when loading. With RAM prices at $200 for 1GB memory 1GB systems will be common during the 2.6 timeframe. There are many possible solutions... 1) add reserve=XXXX to the kernel at boot. Drawback to this is reserving 256-512MB takes this memory out of lowmem kernel use. This will push page tables into highmem slowing the whole system down. 2) Only map a 2048x2048x32 piece of the framebuffer. This still uses 16MB of address space which may not always be available. It could be possible to modify the kernel to always reserve this much address space at boot. 3) Only map what is actually needed on each mode change. Mode change could fail at run time if not enough free address space. 4) Map the buffer into the highmem address space using the highmem access macros. 5) Map the fb in a user process and send it signals to draw. I would also suggest modifying all current fb drivers to print a message about adding reserve=xxxxx at boot if their ioremap() of the fb fails. This will at least point people at an immediate work around. ===== Jon Smirl jonsmirl@yahoo.com __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf