linux-kernel - Re: [Q] How to tell we're using the KMS (during suspend/resume) outside the graphics driver

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Message-Id: <201003091234.59598.rjw@sisk.pl>
Date:	Tue, 9 Mar 2010 12:34:59 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Luca Tettamanti <kronos.it@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	dri-devel@...ts.sourceforge.net
Subject: Re: [Q] How to tell we're using the KMS (during suspend/resume) outside the graphics driver

On Tuesday 09 March 2010, Luca Tettamanti wrote:
> On Sat, Mar 6, 2010 at 10:36 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > Hi,
> >
> > For at least two reasons it would be beneficial for some code outisde the
> > graphics driver(s) to know if the KMS are used.
> >
> > First, in the non-KMS (ie. UMS) case we probably wouldn't want to call
> > acpi_video_resume(), because that has a potential to mess up with the GPU
> > (it actually is known to do that on at least one system).
> >
> > Second, in the KMS case, we'd be able to skip the kernel VT switch, because
> > the KMS driver uses its own framebuffer anyway.
> >
> > So, is there any reasonable way to check that from the outside of the graphics
> > driver?  It should be general enough to cover the cases when there are two
> > graphics adapters with different drivers in the system and so forth.
> 
> Inside the kernel? If you have a struct pci_dev you can get the
> associated struct drm_device with pci_get_drvdata and then check the
> KMS feature: drm_core_check_feature(dev, DRIVER_MODESET).

Yeah, I know that.

> I'm note sure how to check that a device is graphic card though :|

Well, that's the "outside of the graphics driver" part of my question. :-)

Rafael
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