linux-kernel - Re: [PATCH 1/2] PM: make VT switching to the suspend console optional

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Message-ID: <20121102234302.28b773a7@pyramind.ukuu.org.uk>
Date:	Fri, 2 Nov 2012 23:43:02 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	rjw@...k.pl
Subject: Re: [PATCH 1/2] PM: make VT switching to the suspend console
 optional

On Fri,  2 Nov 2012 14:43:40 -0700
Jesse Barnes <jbarnes@...tuousgeek.org> wrote:

> KMS drivers can potentially restore the display configuration without
> userspace help.  Such drivers can set a new global, pm_vt_switch, to
> false if they support this feature.  In that case, the PM layer won't VT
> switch to the suspend console at suspend time and then back to the
> original VT on resume, but rather leave things alone for a nicer looking
> suspend and resume sequence.

What if you are multi-head ? What are the locking rules for a suspend/kms
module unload race, what happens when you load/unload and hand over
multiple frame buffers ? What if you have vts split across two adapters ?

Put me down as 100% in favour of the feature but we need to be a bit more
careful about the implementation. The logic probably needs to be in the
vt layer.

I suspect we actually need a per vt flag for this, or a flag on the
underlying object below the vt somewhere.

So NAK for the implementation ACK for the idea.

Alan
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