From: Ondrej Zajicek <santiago@crfreenet.org>
To: "René Kolařík" <rene.kolarik@seznam.cz>
Cc: linux-fbdev-devel@lists.sourceforge.net
Subject: Re: framebuffer general questions
Date: Fri, 13 Nov 2009 21:08:00 +0100 [thread overview]
Message-ID: <20091113200759.GA5379@localhost> (raw)
In-Reply-To: <1023.2945-18821-2123977998-1258121508@seznam.cz>
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On Fri, Nov 13, 2009 at 03:11:48PM +0100, René Kolařík wrote:
> Hi
>
> i am trying to customize framebuffer drivers and i have some questions...
>
> Please can you give me an advice?
>
> 1) If I define my own imageblit function, how do I call it? Or is it called automatically?
It is called automatically (if it is registered in fb_ops structure)
from kernel console. It is not possible to call it from userspace.
> 2) I have gpu connected via pci to cpu. I did mmap and have
> framebuffer mapped in for example "uchar * data". I have loop and
> iterating through some pixel data and do data[i] = pixel[i]. Does this
> lead to transmitting via PCI in style - transmit byte ... end ...
> transmit byte ... end ... etc?
Probably yes, perhaps there is some write combining according to MTRR
registers.
> 3)what is the difference bethween mmap framebuffer and write to mapped
> pointer and calling write() to descriptor previously obtained by open()?
The first variant is much faster - video RAM is directly mapped to userspace
address space, therefore there is no kernel interaction during writes (in
usual fbdev drivers).
--
Elen sila lumenn' omentielvo
Ondrej 'SanTiago' Zajicek (email: santiago@crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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next prev parent reply other threads:[~2009-11-13 20:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-13 14:11 framebuffer general questions René Kolařík
2009-11-13 20:08 ` Ondrej Zajicek [this message]
2009-11-15 23:28 ` René Kolařík
2009-11-16 0:06 ` Ondrej Zajicek
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