OLS: The state of Linux wireless networking [LWN.net]

OLS: The state of Linux wireless networking

Posted Aug 2, 2008 19:53 UTC (Sat) by giraffedata (subscriber, #1954)
In reply to: OLS: The state of Linux wireless networking by cortana
Parent article: OLS: The state of Linux wireless networking

That's great information; I have filed it where there's a chance I will find it next time I have this problem.

I'm in the tiny system boat -- not that I'm working with an embedded system, but it's still more cost than it's worth to include a device driver for a device that there's only a one in a thousand chance I'll ever have. So when I do add a device, I have this exercise of determining which driver it needs (and if one even exists).

It looks like a modules.pcimap from a full, current Linux system is the directory I've been looking for.

Incidentally, an important class of device driver that isn't covered by this is X video controller drivers. I recently changed a video controller, on what I think is a fully conventional Debian system, and it was a more-painful-than-Windows experience getting Linux (i.e. x.org) to work with it. And even then, it would not do DVI, which I eventually concluded is because Linux driver software that can do that simply doesn't exist. That's an example of the problem that started this thread: How do you know what works and what doesn't on Linux -- even with modules.pcimap?

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OLS: The state of Linux wireless networking

Posted Aug 2, 2008 20:23 UTC (Sat) by tialaramex (subscriber, #21167) [Link]

The X video drivers are also supposed to be auto-selected based on a similar principle. You
don't specify what type of video hardware you had, so we can only speculate as to why it
didn't work but you don't need to configure modern X servers to make them work. Without a
configuration the server should detect your PCI/AGP/PCIe etc. graphics chipset and load the
appropriate driver, and the driver should (if your display is switched on) pick the right
output and a working video mode.

Thus, try removing the configuration file and starting the X server. If this doesn't work in
current X.org, and you have a card which is actually supported at all, you should report it as
a bug, attaching the X server logs.

Annoyingly there are a few things which won't work correctly without a configuration file, but
it should at least be usable and you should consider filing bugs about anything that doesn't
work (I have an open bug about the R400 driver defaulting to XAA then complaining that XAA is
unsupported and suffering some redraw bugs as a result)

The latest chipsets from the major vendors don't work (or work poorly) unless you are willing
to use the vendor's proprietary drivers (and in that case any problems should be taken up with
them). Don't buy stuff aimed at Windows gamers with too much money.

The mention of DVI makes me wonder if you had something more serious wrong though, DVI ought
to work with the hardware-specific drivers for Intel or ATI hardware old enough to be
supported, or even with a lot of nVidia cards - you are seeing text through this DVI connector
prior to X starting, right ?

Linux device driver availability (wasOLS: The state of Linux wireless networking)

Posted Aug 2, 2008 21:23 UTC (Sat) by giraffedata (subscriber, #1954) [Link]

Thus, try removing the configuration file and starting the X server.

I ultimately did essentially that. But if you have to remove a file in order to use a new video controller, you're already in more-painful-than-Windows territory. Especially if you have to find an expert like you to tell you to do it.

The mention of DVI makes me wonder if you had something more serious wrong though, DVI ought to work with the hardware-specific drivers for Intel or ATI hardware old enough to be supported, or even with a lot of nVidia cards - you are seeing text through this DVI connector prior to X starting, right ?

No, I've never seen anything come out of the DVI connector, and I tried every scenario except putting the card in a Windows machine. It's a Matrox G400; the 'mga' driver man page, and some morsels I found on the web, suggest that you have to specifically turn on DVI and the only known software that can do that is a closed source X module from Matrox and Matrox does not offer a version compatible with the X server in my Debian Etch system.

This is just the card that was laying around. But if I had set out to buy something to drive my DVI monitor, I don't know how I would have known what to choose.

Linux device driver availability (wasOLS: The state of Linux wireless networking)

Posted Aug 3, 2008 9:13 UTC (Sun) by tialaramex (subscriber, #21167) [Link]

Well, I guess my point was more that the distro oughtn't to create this file in the first
place. One of X.org's biggest problems these days seems to be the little programs that Linux
distributors knocked together in Perl or C ten years ago that try to create a "correct"
configuration, often at install time. Obviously anything that the distro manually configures
at install time and which subsequently needs changing is going to be a pain for the user.

We can't really blame the distributors for doing this back when XFree86 wasn't smart enough to
just pick a working driver and configure it, but we can blame them for not re-assessing this
decision some time between when X was first able to run without configuration and today. By
the point when Etch was released such a file was necessary for only a tiny minority of users,
and so it should not be written by default.

You won't have to remove the file again - it should stay gone (unless sadly you have to
recreate it due to one of the outstanding limitations of the auto-configured X server, but
fixing these ought to be a priority)

I have to say I did not realise that they made G400s with DVI, I guess it figures given the
niche where Matrox makes money but it was still a surprise to me. My G400 just had a single
VGA output. Yeah, that chipset is not well supported and mine has been in a junk pile for some
number of years. Apparently its video BIOS doesn't enable the DVI output (else you'd see
something) so that means it's not just Linux, any OS without explicit support for that
hardware won't work with DVI on that chip, which is pretty sad.

I don't think there's much chance that anyone will look at a nearly 10 year old chip now and
think "Ooh, reverse engineering the DVI output looks like a fun project for a rainy weekend"
so you may be SOL, sorry. And I can see how you'd feel misled, the G400 is documented as
working, without a caveat about that DVI output.

X configuration files, DVI on the G400

Posted Aug 8, 2008 12:40 UTC (Fri) by anton (guest, #25547) [Link]

Yes, on all the Radeon cards I have tried Debian (and its derivatives) creates an xorg.conf file that does not work, and if I delete it and start X, the card just works beautifully. Its as if Debian and its derivatives were staffed by Nvidia employees.

Concerning the Matrox G400, I used to use a G450, and its DVI output has a rather limited bandwidth that allows only 1280x1024 with regular modes. I used a special mode to make it display 1600x1200.

OLS: The state of Linux wireless networking

Posted Aug 4, 2008 11:26 UTC (Mon) by daenzer (✭ supporter ✭, #7050) [Link]

> (I have an open bug about the R400 driver defaulting to XAA then
> complaining that XAA is unsupported and suffering some redraw bugs as a
> result)

Which bug report is that? The radeon driver doesn't say that XAA is unsupported but that
RENDER acceleration is unsupported with XAA (on >= R300 cards). As for XAA rendering
corruption, make sure its offscreen pixmap support is disabled (the default in current X
servers).