doubts

doubts

[Manish RATHI]

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Hi,
In franebuffer  fb_info structure, there are 4 functions to be used by fbcon.c 
these are:

(*updatevar)();
(*changevar)();
(*blank)();

Could anybody tell me the logic of above functions. Although they are mentioned in pl110.c and vfb.c but only function header is given.


Regards
Manish




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Re: doubts

[Lucas Correia Villa Real]

On Wednesday 26 May 2004 08:40, Manish RATHI wrote:
> Hi,
> In franebuffer  fb_info structure, there are 4 functions to be used by
> fbcon.c these are:

4? You asked for 3 functions :-)


> (*updatevar)();

This is a function called by fbcon.c when going to update a user defined part 
of the display, in order to pan/wrap; updatevar() usually sets the new 
driver's "var" xoffset and yoffset and then tells the video controller the 
new screen start address. 


> (*changevar)();

Oh, I didn't see any driver using that. In the case of fbcon_changevar, it 
just calls fbcon_setup (specifying not to show the logo again), which resets 
the framebuffer settings such as font and pan/wrap offsets. 

When one calls (*setvar)(), which modifies the display variable configuration, 
it checks for the existence of a non-null function pointer to changevar and 
if found, calls that function. I really don't know why a driver should need 
to restart things when changing var data. Could anyone help to clarify that?

> (*blank)();

This function does the screen blanking routine, not required to be implemented 
by the driver. There's a good explanation of it on skeletonfb.c.


> Could anybody tell me the logic of above functions. Although they are
> mentioned in pl110.c and vfb.c but only function header is given.
>
>
> Regards
> Manish

Cheers,
Lucas


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Re: doubts

[Geert Uytterhoeven]

On Fri, 28 May 2004, Lucas Correia Villa Real wrote:
> On Wednesday 26 May 2004 08:40, Manish RATHI wrote:
> > (*changevar)();
>
> Oh, I didn't see any driver using that. In the case of fbcon_changevar, it
> just calls fbcon_setup (specifying not to show the logo again), which resets
> the framebuffer settings such as font and pan/wrap offsets.
>
> When one calls (*setvar)(), which modifies the display variable configuration,
> it checks for the existence of a non-null function pointer to changevar and
> if found, calls that function. I really don't know why a driver should need
> to restart things when changing var data. Could anyone help to clarify that?

It's there so fbcon can resize the emulated text console based on the new
screen size. E.g. when switching from 640x480 to 1024x768 using fbset, the text
console will change from 80x30 to 128x48 (assuming a 8x16 font).

It's broken in 2.6, though (unless it got fixed while I was on holidays last
week :-)

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds


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