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List:       linux-fbdev-users
Subject:    [Linux-fbdev-users] Re: [Linux-fbdev-devel] "remap_page_range" i810 compile time problem ..
From:       "Antonino A. Daplas" <adaplas () hotpop ! com>
Date:       2005-03-11 11:05:26
Message-ID: 200503111905.27355.adaplas () hotpop ! com
[Download RAW message or body]

On Friday 11 March 2005 14:36, Mukund JB. wrote:
> Hi adaplas,
>
> Thankful to u for making things clear at every level.
>
> > > But when I try this without accel=1 rotation fails. Can u just
>
> narrate
>
> > > me what is accel accentually doing?
> >
> > Because if accel is on, the driver is using it's own version of
>
> drawing
>
> > functions which are flexible enough that additional features can be
>
> added,
>
> > such as screen rotation.
> >
> > If accel is off, the driver will use the generic functions which
>
> cannot do
>
> > screen rotation.  Of course, one can write a software version that can
>
> do
>
> > screen rotation.
>
> So, u mean the i810fb driver will process the command line parameters &
> if finds the accel is "1" in the list, it will use its own functions or
> else it will use the generic functions provided in the fbgen.c file.

Above is correct, except that i810fb, if accel is disabled will use the
functions in fbcon-cfb*.c, not fbgen.c.

>
> This is my understanding about fb driver architecture
>
> 			Application
> 			-----------
> 		  XFree86 / Directfb (Embedded)
> 			-----------
> 			 FB driver
> 			-----------
> 			 HARDWARE
>
> Are these files below a part of fb driver or do they come under a
> different level in fb driver architecture?

The above is correct, assuming that XFree86 uses the 'fbdev' driver.

>
> fbcon.c - low level framebuffer based console driver
> fbcon-cfb* - low level framebuffer based operations for 8 bpp packed
> pixels
> How do I differentiate between the above two?

fbcon.c is the glue between console and fbdev.  fbcon-cfb* contains
generic drawing functions for framebuffers with packed pixel format.

>
> fbcmap.c 	- It handles color mapping
> fbcon-plan2p*
>
> I find fbdevhw.a & I find groups referring to it.

fbdevhw, if I'm not mistaken, came from XFree86/Xorg.  It contains
helper functions used by XFree86 to talk to fbdev.

> I think it is a library. If so, give me some inputs where we can use it.
> Please do correct if I am going OFF-TRACK understanding FB drivers.
>
> Where exactly should I place the fbdevhw.a in the above shown
> architecture?

Probably between  XFree86 and fbdev.

Tony





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