Re: [PATCH] Add fb_check_var() for fixed mode device.

[Helge Deller <deller@gmx.de>]

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Michel Dänzer wrote:
> On Fri, 2008-08-29 at 16:14 +0200, Geert Uytterhoeven wrote:
>> On Fri, 29 Aug 2008, Michel Dnzer wrote:
>>> On Fri, 2008-08-29 at 14:16 +0200, Geert Uytterhoeven wrote:
>>>> | X.Org X Server 1.4.2
>>> [...]
>>>
>>>> | (EE) FBDEV(0): FBIOPUT_VSCREENINFO succeeded but modified mode
>>> [...]
>>>
>>>> Hence Xorg is broken on all embedded devices with a frame buffer driver
>>>> that supports a single fixed video mode only?
>>> No. As discussed before, you're probably missing
>>>
>>> http://cgit.freedesktop.org/xorg/xserver/commit/?id=c095da04fe7c73b6503ef5b93549b13796c51b22
>>>
>>> which is in the upcoming xserver 1.5 release.
>> Ah, upcoming. That's not current/previous/... ;-)
> 
> Yeah, it might have been nice to backport this to the 1.4 branch, but
> it's kind of too late now. Of course, you can always bug your
> distributor to backport it. :)

The attached patch is a completely different approach to solve the 
issue. I've tested it, and it works even with the buggy version of X 
(1.4.2).

Basic idea is, that when we have fixed mode devices (aka drivers which 
don't implement fb_check_var) we just simply fill in a "emulated" valid 
monitor/modeline into the var struct during the register_framebuffer() 
initialization call. Since the modeline is valid, X does not has any 
problems with it.

The patch has a few benefits:
a) We still keep binary compatability/behavior for FBIOGET_VSCREENINFO 
and FBIOPUT_VSCREENINFO.
b) In Xorg.conf files, users can simply delete all monitor and display 
sections -> Xorg will autoconfigure itself to the only valid 
resolution/modeline itself on all devices (I really like this!!!)

Thus, the patch basically changes the fixed mode drivers to have some 
monitor timings by default. As an example, before I got:
root@c3000:~# fbset -i
mode "1024x768"
     geometry 1024 768 1024 768 8
     timings 0 0 0 0 0 0 0
     rgba 8/0,8/0,8/0,0/0
endmode

Now I see:
root@c3000:~# fbset -i
mode "1024x768-60"
     # D: 65.003 MHz, H: 48.365 kHz, V: 60.006 Hz
     geometry 1024 768 1024 768 8
     timings 15384 168 8 29 3 144 6
     rgba 8/0,8/0,8/0,0/0
endmode

Opinions ?

Signed-off-by: Helge Deller <deller@gmx.de>



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diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 98843c2..72b3113 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -1470,9 +1470,23 @@ register_framebuffer(struct fb_info *fb_info)
 	if (!fb_info->pixmap.blit_y)
 		fb_info->pixmap.blit_y = ~(u32)0;
 
-	if (!fb_info->modelist.prev || !fb_info->modelist.next)
+	if (!fb_info->modelist.prev || !fb_info->modelist.next) {
 		INIT_LIST_HEAD(&fb_info->modelist);
 
+		/* For drivers which does not support mode setting
+		 * initialize an emulated modeline */
+		if (!fb_info->fbops->fb_check_var &&
+		     fb_info->var.pixclock == 0) {
+			char modestr[32];
+			snprintf(modestr, sizeof(modestr), "%dx%d-%d",
+				fb_info->var.xres,
+				fb_info->var.yres,
+				fb_info->var.bits_per_pixel);
+			fb_find_mode(&fb_info->var, fb_info, modestr,
+				NULL, 0, NULL, fb_info->var.bits_per_pixel);
+		}
+	}
+
 	fb_var_to_videomode(&mode, &fb_info->var);
 	fb_add_videomode(&mode, &fb_info->modelist);
 	registered_fb[i] = fb_info;

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