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

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Date:	Tue, 9 Mar 2010 12:01:18 +0100
From:	Luca Tettamanti <kronos.it@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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 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).
I'm note sure how to check that a device is graphic card though :|

Luca
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