From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 17 Oct 2000 13:37:58 +0200 (CEST) From: Geert Uytterhoeven To: Samuel Rydh cc: Linux/PPC Development , bh40@calva.net, linux-fbdev@vuser.vu.union.edu Subject: Re: [linux-fbdev] Re: Video driver bug In-Reply-To: <20001017002037.A26630@ibrium.se> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: On Tue, 17 Oct 2000, Samuel Rydh wrote: > On Mon, Oct 16, 2000 at 05:22:58PM -0700, James Simmons wrote: > > > > > Well, my understanding is that MOL needs to be able to "probe" for all > > > > > supported mode. Doing so on a visible console would definitely be hell. > > > > > It does that in order to setup the MacOS-side driver mode list. > > > > > > > > According to Samuel's last post, MOL needs both var and fix for probing. > > > > Yes this is really bad. The way most drivers are written is that testing > > var does not change fix. If you grab fix after testing the video mode it > > will be for the current set resolution. Not the one you are testing > > for. For most drivers you need to physically set the mode to change > > fix. Sometimes the information in fix can only be obtained from the > > hardware and this requires a video mode change. > > What MOL needs from the fix structure is the bytes_per_line field and > the page_offset of framebuffer. This information is necessary in order > to make it possible to switch seamlessly (by using the MMU) from a > RAM based framebuffer to the physical one. OK. > What I'd like to see is good way to obtain these parameters without > actually setting the video mode. And, of course, it would be nice Currently that's possible, but it will no longer be in the future. But I guess it's only a few modes (640x400, 800x600, 1024x768, 1280x1024), so it won't cause too much annoyance? Alternatively you can get the info once and store it in a config file in the user's homedir. If it later turns out to be invalid (e.g. due to dual-head issues, or because you changed your video card), you can offer to reprobe when restarting MOL the next time. > if they were guaranteed to be constant for a given video mode. That depends on the hardware. When you're running on the second head of e.g. a Matrox G400, it cannot be guaranteed. So MOL should test whether those values are still valid when switching from X to the console, and return to X when they are no longer valid. Is this acceptable? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/