xorg-x11-drv-ati for Fedora 10 fails to setup DRI for 3520x1600x32 screen, is this normal?

[Alex Villací­s Lasso]

I am checking out what happens when I disable kernel modesetting for a 
radeon chipset (Xpress 200M RC410) with the xorg-x11-drv-ati package 
from updates-testing in Fedora 10. So far I have seen that the driver 
refuses to enable DRI support, as it claims that 64Mb is not enough 
memory. I added a patch to the source RPM to check what is happening, 
and I get this on the logs:

(II) RADEON(0): RADEONInitMemoryMap() :
(II) RADEON(0):   mem_size         : 0x04000000
(II) RADEON(0):   MC_FB_LOCATION   : 0x3fff3c00
(II) RADEON(0):   MC_AGP_LOCATION  : 0xffffffc0
(II) RADEON(0): Depth moves disabled by default
(==) RADEON(0): Using accelerated EXA DownloadFromScreen hook
(II) RADEON(0): Allocating from a screen of 65536 kb
(II) RADEON(0): Will use 32 kb for hardware cursor 0 at offset 0x0157c000
(II) RADEON(0): Will use 32 kb for hardware cursor 1 at offset 0x01580000
(II) RADEON(0): Will use 22000 kb for front buffer at offset 0x00000000
(II) RADEON(0): Will use 22000 kb for back buffer at offset 0x01584000
(II) RADEON(0): Will use 10624 kb for textures at offset 0x02b00000
(II) RADEON(0): Will use 10880 kb for X Server offscreen at offset 
0x03560000
(II) RADEON(0): displayWidth=3520 virtualY=1600 pixel_bytes=4 
FbMapSize=67108864 maxy=4766
(EE) RADEON(0): Static buffer allocation failed.  Disabling DRI.
(EE) RADEON(0): At least 66000 kB of video memory needed at this 
resolution and depth.

The patch shows that the required video memory is being calculated from 
a screen resolution of 3520 x 1600. This happens to be the maximum 
supported dimensions as reported from the output of xrandr:

[alex at srv64 ~]$ xrandr
Screen 0: minimum 320 x 200, current 1440 x 1080, maximum 3520 x 1600
VGA-0 connected 1440x1080+0+0 (normal left inverted right x axis y axis) 
306mm x 230mm
   1440x1080      62.1*+
   1600x1200      60.0 
   1400x1050      63.3 
   1280x1024      60.0 
   1280x960       60.0 
   1152x864       75.0 
   1024x768       85.0     75.0     70.1     60.0     43.5 
   832x624        74.6 
   800x600        85.1     85.1     72.2     75.0     60.3     56.2 
   640x480        85.0     75.0     72.8     75.0     66.7     59.9 
   720x400        87.8     85.0     70.1 
   640x400        85.1 
   640x350        85.1 
S-video disconnected (normal left inverted right x axis y axis)

As you can see, my primary (and only) screen is using a resolution of 
1440x1080, the maximum one it supports. But the DRI calculation is being 
done on 3520 x 1600. Is this the normal behavior of the X server and the 
radeon driver? I am not really sure, so I am asking here instead of 
filing a bug. Is there any directive on xorg.conf I can use to reduce 
the xrandr maximum so that it can fit within the DRI calculation for my 
system?

-- 
perl -e '$x=2.3;printf("%.0f + %.0f = %.0f\n",$x,$x,$x+$x);'