Bug 10756 - intel driver not enabling correct DPI
Summary: intel driver not enabling correct DPI
Alias: None
Product: xorg
Classification: Unclassified
Component: Driver/intel (show other bugs)
Version: unspecified
Hardware: x86 (IA32) All
: medium normal
Assignee: Hong Liu
QA Contact: Xorg Project Team
: 10728 (view as bug list)
Depends on:
Blocks: 13027
  Show dependency treegraph
Reported: 2007-04-25 03:31 UTC by Kalev Lember
Modified: 2007-11-01 00:13 UTC (History)
8 users (show)

See Also:
i915 platform:
i915 features:

Xorg server log (36.42 KB, text/plain)
2007-04-25 03:33 UTC, Kalev Lember
no flags Details
Xorg config file (3.95 KB, text/plain)
2007-04-25 03:34 UTC, Kalev Lember
no flags Details

Description Kalev Lember 2007-04-25 03:31:32 UTC

I am using intel driver 2.0.0 on Xorg 1.3.0 server. Problem is that it doesn't use correct DPI for LVDS output. From Xorg.0.log:

First it says:
(**) intel(0): Display dimensions: (300, 230) mm
(**) intel(0): DPI set to (86, 113)

which is correct.

But then a while later:
(II) intel(0): Setting screen physical size to 270 x 203

which is clearly wrong, because it uses 96*96 DPI and resolution to calculate this size.

Setting DisplaySize in xorg.conf seems to make no difference in what DPI is used.

  dimensions:    1024x768 pixels (270x203 millimeters)
  resolution:    96x96 dots per inch

If I connect external LCD screen to VGA output, then DPI is correctly set for the external LCD screen. The "old" i810 driver without modesetting branch used correct DPI for LVDS (laptop screen).

Thanks a lot,
Kalev Lember
Comment 1 Kalev Lember 2007-04-25 03:33:28 UTC
Created attachment 9736 [details]
Xorg server log
Comment 2 Kalev Lember 2007-04-25 03:34:10 UTC
Created attachment 9737 [details]
Xorg config file
Comment 3 Johannes Engel 2007-05-14 09:21:38 UTC
I can confirm that. I have got a "DisplaySize" directive in my xorg.conf which seems to be omitted.
Comment 4 Johannes Engel 2007-05-14 09:22:47 UTC
*** Bug 10431 has been marked as a duplicate of this bug. ***
Comment 5 Johannes Engel 2007-05-14 09:23:56 UTC
*** Bug 10427 has been marked as a duplicate of this bug. ***
Comment 6 Johannes Engel 2007-05-14 09:28:24 UTC
*** Bug 10728 has been marked as a duplicate of this bug. ***
Comment 7 Johannes Engel 2007-05-14 09:31:57 UTC

*** This bug has been marked as a duplicate of bug 10304 ***
Comment 8 Eric Anholt 2007-05-14 11:34:47 UTC
Unmark as a dupe of an unrelated bug.
Comment 9 Eric Anholt 2007-05-14 14:01:28 UTC
Looks like the compat_output is chosen to be VGA, despite not being connected.
Comment 10 Johannes Engel 2007-05-14 15:36:38 UTC
Do you need any further information?
Comment 11 alium 2007-07-01 06:52:30 UTC
please read http://bugs.archlinux.org/task/7129

I find problem in driver intel : driver intel  read not correctly info from DDC and set up wrong dimensions/resolution :

before :

xdpyinfo |grep -A1 dimensions
dimensions: 1280x800 pixels (289x21 millimeters)
resolution: 112x968 dots per inch

FIX: to Section "Device" add line Option "DDC" "no"

xdpyinfo |grep -A1 dimensions
dimensions: 1280x800 pixels (338x211 millimeters)
resolution: 96x96 dots per inch

i know, is small hack, but works good ==> fix driver intel 

P.S. :sorry for my english, is bad
Comment 12 Johannes Engel 2007-07-04 02:00:17 UTC
Maybe it works for you, but it does not fix the problem, since the option "DDC" is only specified for the i810 and i815 chipsets (see man intel).
Comment 13 Johannes Engel 2007-07-04 02:02:34 UTC
The problem persists with xf86-video-intel-2.1.0
Comment 14 Jonh Wendell 2007-08-04 08:32:46 UTC
The solution from Alois Nespor worked for me. Now i have 96x96 DPI :)
I have a 915GM card in a Dell laptop.
Comment 15 Eric Anholt 2007-08-09 15:16:19 UTC
    HorizSync   31.5-105
    VertRefresh 40-150

You're specifying ranges beyond the capability of your monitor.  Please remove them (and probably the rest of the custom configuration) and try again.
Comment 16 Eric Anholt 2007-08-09 15:18:45 UTC
gah, wrong tab.
Comment 17 alium 2007-09-03 23:43:27 UTC
The problem with driver intel is in driver:

Common issues not caused by the driver
- Font sizes (DPI) are wrong.  Some displays incorrectly report their
  physical size, which is harmless on most OSes that always assume 96dpi
  displays.  This can be fixed through quirks for specific monitors in the X
  Server, and the output of xrandr --prop along with a physical measurement of
  the screen size in a bug report against the server can help get that fixed.

When is not driver fixed, will wrong DPI persist. It posibble, that error will fixed in new X.org 7.3 (xserver 1.4, xrandr 1.2) what are get out 5.September 2007. 
Comment 18 Hong Liu 2007-10-09 00:22:21 UTC
Please try the patch attached in comment 14 of bug 10304.
Comment 19 Jesse Barnes 2007-10-31 13:39:38 UTC
Is this still a problem?  This may also be a gtk or other problem even if the driver is fixed.
Comment 20 alium 2007-11-01 00:13:50 UTC
This problem is resolved from https://bugs.freedesktop.org/show_bug.cgi?id=10304 -  intel driver now set correct DPI, the patch will in xorg-server 1.4.1 and must be the right set xorg.conf

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