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)
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"To err is human -- to blame it on a computer is even more so."