> The driver sets a video mode and then checks if the syscall modified the
> parameters with the function fbdev_modes_equal():
>
> --snip--
> /* static*/ Bool
> fbdev_modes_equal(struct fb_var_screeninfo *set, struct
> fb_var_screeninfo *req)
> {
> return (set->xres_virtual >= req->xres_virtual &&
> set->yres_virtual >= req->yres_virtual &&
> set->bits_per_pixel == req->bits_per_pixel &&
> set->red.length == req->red.length &&
> set->green.length == req->green.length &&
> set->blue.length == req->blue.length &&
> set->xres == req->xres && set->yres == req->yres &&
> set->pixclock == req->pixclock &&
> set->right_margin == req->right_margin &&
> set->hsync_len == req->hsync_len &&
> set->left_margin == req->left_margin &&
> set->lower_margin == req->lower_margin &&
> set->vsync_len == req->vsync_len &&
> set->upper_margin == req->upper_margin &&
> set->sync == req->sync && set->vmode == req->vmode);
The is the kernel's implementation:
int fb_mode_is_equal(const struct fb_videomode *mode1,
const struct fb_videomode *mode2)
{
return (mode1->xres == mode2->xres &&
mode1->yres == mode2->yres &&
mode1->pixclock == mode2->pixclock &&
mode1->hsync_len == mode2->hsync_len &&
mode1->vsync_len == mode2->vsync_len &&
mode1->left_margin == mode2->left_margin &&
mode1->right_margin == mode2->right_margin &&
mode1->upper_margin == mode2->upper_margin &&
mode1->lower_margin == mode2->lower_margin &&
mode1->sync == mode2->sync &&
mode1->vmode == mode2->vmode);
}
> Tracing with gdb gives the following:
>
> Breakpoint 1, fbdev_modes_equal (set=0xfb5ed568, req=0xfb5ed4c8)
> at ../../../../hw/xfree86/fbdevhw/fbdevhw.c:256
> 256 }
> (gdb) p *set
> $1 = {xres = 1024, yres = 768, xres_virtual = 1024, yres_virtual = 768,
> xoffset = 0, yoffset = 0,
> bits_per_pixel = 8, grayscale = 0, red = {offset = 0, length = 8,
> msb_right = 0}, green = {offset = 0,
> length = 8, msb_right = 0}, blue = {offset = 0, length = 8,
> msb_right = 0}, transp = {offset = 0,
> length = 0, msb_right = 0}, nonstd = 0, activate = 0, height = 0,
> width = 0, accel_flags = 0,
> pixclock = 0, left_margin = 0, right_margin = 0, upper_margin = 0,
> lower_margin = 0, hsync_len = 0,
> vsync_len = 0, sync = 0, vmode = 0, reserved = {0, 0, 0, 0, 0, 0}}
>
> (gdb) p *req
> $2 = {xres = 1024, yres = 768, xres_virtual = 1024, yres_virtual = 768,
> xoffset = 0, yoffset = 0,
> bits_per_pixel = 8, grayscale = 0, red = {offset = 0, length = 8,
> msb_right = 0}, green = {offset = 0,
> length = 8, msb_right = 0}, blue = {offset = 0, length = 8,
> msb_right = 0}, transp = {offset = 0,
> length = 0, msb_right = 0}, nonstd = 0, activate = 0, height = 0,
> width = 0, accel_flags = 0,
> pixclock = 22271, left_margin = 56, right_margin = 8, upper_margin =
> 41, lower_margin = 0,
> hsync_len = 176, vsync_len = 8, sync = 3, vmode = 1, reserved = {0,
> 0, 0, 0, 0, 0}}
>
> (gdb) bt
> #0 fbdev_modes_equal (set=0xfb5ed568, req=0xfb5ed4c8) at
> ../../../../hw/xfree86/fbdevhw/fbdevhw.c:256
> #1 0x40bcfb64 in fbdevHWSetMode (pScrn=0x2142a0, mode=<value optimized
> out>, check=1)
> at ../../../../hw/xfree86/fbdevhw/fbdevhw.c:528
> #2 0x40bd07e8 in fbdevHWSetVideoModes (pScrn=0x2142a0) at
> ../../../../hw/xfree86/fbdevhw/fbdevhw.c:568
> #3 0x40cf5bec in ?? () from /usr/lib/xorg/modules/drivers//fbdev_drv.so
> #4 0x00074e88 in InitOutput ()
> #5 0x00039d04 in main ()
>
> As you can see, the main video parameters are OK, while the
> monitor/modeline values (pixclock, left_margin, right_margin,
> upper_margin, lower_margin, hsync_len, vsync_len, sync and vmode)
> were changed to zero.
> Any ideas?
Given that the kernel considers the above as part of the video mode,
I believe that this is a kernel bug.
Dave
--
J. David Anglin dave.anglin@xxxxxxxxxxxxxx
National Research Council of Canada (613) 990-0752 (FAX: 952-6602)
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