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."