linux-kernel - Re: Proposal for a low-level Linux display framework

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Message-ID: <20110915200514.74bdcd90@lxorguk.ukuu.org.uk>
Date:	Thu, 15 Sep 2011 20:05:14 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Florian Tobias Schandinat <FlorianSchandinat@....de>
Cc:	Keith Packard <keithp@...thp.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, linaro-dev@...ts.linaro.org,
	"Clark\, Rob" <rob@...com>, Archit Taneja <archit@...com>
Subject: Re: Proposal for a low-level Linux display framework

> What is your problem with discontigous framebuffers? (I assume discontigous
> refers to the pages the framebuffer is composed of)
> Sounds to me like you should implement your own fb_mmap and either map it
> contigous to screen_base or implement your own fb_read/write.
> In theory you could even have each pixel at a completely different memory
> location although some userspace wouldn't be happy when it could no longer mmap
> the framebuffer.

The mmap side is trivial, the problem is that the fb layer default
implementations of blits, fills etc only work on a kernel linear frame
buffer. And (for example) there is not enough linear stolen memory on
some Intel video for a 1080p console on HDMI even though the hardware is
perfectly capable of using an HDTV as its monitor. Nor - on a 32bit box-
is there enough space to vremap it.

Alan
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