LCA: Updates on the X Window System [LWN.net]

LCA: Updates on the X Window System

Posted Jan 23, 2007 1:48 UTC (Tue) by neilbrown (subscriber, #359)
In reply to: LCA: Updates on the X Window System by drag
Parent article: LCA: Updates on the X Window System

My understanding from Keith's talk at LCA is that the Intel graphics chip
doesn't actually control mode setting at all. It somehow leaves that for
some other glue chip that the motherboard manufacturer needs to provide.
(Apparently this is similar to the AC97 sound architecture where the
analogue bits were not in the Intel chipset, only the digital bits).

The interface to these mode-setting glue chips is not standardised
so everybody does it differently. So for Xorg to be able to do
mode setting, it with has to know about how all the different glue
chips work (Which is what the new mode-setting branch of the driver tries)
or it needs help from the VBIOS (which is what the 'stable' branch does).

So maybe it is Intel's fault for not standardising the interface properly,
and very likely it is Intel's fault if you have an Intel motherboard, but
the situation doesn't seem to be as straight forward as one might like it to be.

to post comments

LCA: Updates on the X Window System

Posted Jan 23, 2007 6:51 UTC (Tue) by keithp (subscriber, #5140) [Link] (4 responses)

Intel chips have some outputs built-in and rely on external chips for other outputs. G965 has only VGA built-in, and relies on SDVO for DVI and TV-out. Mobile chips (915GM, 945GM) have built-in LVDS and TV out as well, so there's no external chip driver needed for most operations.

The Intel driver has relied for far too long on BIOS-based modesetting, and after I joined Intel, replacing that became our highest priority. While initial support for LVDS and VGA was running early last year, getting the remaining outputs working correctly has taken a long time. Of course, all of that would have been a lot easier if we hadn't also been working on RandR 1.2 at the same time.

LCA: Updates on the X Window System

Posted Jan 23, 2007 14:43 UTC (Tue) by sylware (guest, #35259) [Link] (2 responses)

BTW, why "CRTC"? In randr 1.2, "CRTC"s are not really dealing only with Cathod Ray Tubes. Maybe a more appropriate name should be chosen since you have control over the API. I do realize it's a rather super minor detail.

LCA: Updates on the X Window System

Posted Jan 23, 2007 15:51 UTC (Tue) by jzbiciak (guest, #5246) [Link]

And what about these plotters that are actually printers, SCSI disks that are actually flash drives, and TTYs that haven't seen a teletype in decades? Next you'll be telling me that the primary use of TAR files really is tape backup! ;-) ;-) ;-)

LCA: Updates on the X Window System

Posted Jan 23, 2007 18:02 UTC (Tue) by bronson (subscriber, #4806) [Link]

Because "CRTC" is an industry term that is older than I am. All video driver writers know what you're talking about when you say "CRTC" regardless of platform or API.

Besides, what should it be replaced with? LCDC? And then replace that 5 years later with LEDC? :)

LCA: Updates on the X Window System

Posted Jan 23, 2007 23:51 UTC (Tue) by gdt (subscriber, #6284) [Link]

Thank you Keith, as the Intel driver's BIOS calls are somewhat problematic on the Mac Mini (requiring the installation of the Bootcamp BIOS emulator, thus during-boot keystrokes are required to select the Linux operating system else it boots MacOS).