On Mon, 2009-06-22 at 18:18 -0700, Jesse Barnes wrote: > On Tue, 23 Jun 2009 11:04:39 +1000 > Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote: > > > On Mon, 2009-06-22 at 17:24 -0700, Linus Torvalds wrote: > > > > > > On Tue, 23 Jun 2009, Benjamin Herrenschmidt wrote: > > > > > > > > As far as I can remember, all fbdev operations are done under the > > > > console semaphore. > > > > > > Yeah, and some of them are horribly broken (ie copying data from > > > user space while doing it - causing horrible things like VC > > > switching latencies and invisible printk's if an oops happens > > > during the op). > > > > > > Or maybe that got fixed. > > > > Well, it does rely on userspace behaving.. ie, no accel ops are done > > by the kernel in KD_GRAPHICS and userspace is -supposed- to switch to > > KD_GRAPHICS before touching the fb. > > > > In fact, nowdays, we do have the infrastructure to be smart and > > enforce that. IE. Instead of using a boring remap_page_ranges() in > > fb_mmap() we could use a fault handler. When in KD_TEXT, we fail > > them, when in KD_GRAPHICS, we service them, and we > > unmap_mapping_range() when switching. Something like that... > > > > Dunno how that interacts with the new DRM thingy though. > > I think it could work, but ideally we'd keep the kernel fbcon object > pinned, and keep printing into it even while some other gfx app is > running.
It doesn't need to be pinned for that, does it? I think in the long run it's a bad idea to have it pinned all the time, think of machines with only 8 MB of VRAM... > (something like this would also be handy for dual head debugging; one > head running your desktop and the other a debug console printing all > the messages). On a side note, I did precisely that about ten years ago on my Amiga. :) Granted, that was using two separate framebuffer devices (X glint driver on top of pm2fb, debug messages on amifb), but I think even that case isn't possible ATM. I agree it would be nice, though realistically there's hardly a way around a second machine for graphics driver development anyway. -- Earthling Michel Dänzer | http://www.vmware.com Libre software enthusiast | Debian, X and DRI developer ------------------------------------------------------------------------------ Are you an open source citizen? Join us for the Open Source Bridge conference! Portland, OR, June 17-19. Two days of sessions, one day of unconference: $250. Need another reason to go? 24-hour hacker lounge. Register today! http://ad.doubleclick.net/clk;215844324;13503038;v?http://opensourcebridge.org -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
