Re: [PATCH] Do set var even if no fb_check_var() provided.

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Wed, 27 Aug 2008, Takashi Yoshii wrote:
> The behavior of FBIOSET_VSCREENINFO seems to be weired on FB which does not
>  provides fbops->fb_check_var.
> It doesn't set anything, but gets info->var instead, and returns no error.
> It is just same as FBIOGET_VSCREENINFO does.
> 
> IMHO, this should be one of the following candidates,
>  1. set var without check.
>  2. do nothing but return error (setting var is not supported).
> or
>  3. it's a bug (fb_check_var should always be provided).
> 
> The patch at the bottom implements "1".
> 
> Because I don't know API specification, nor the history of the code, 
> I would like people who knows well to discuss this.

If the driver doesn't provide a fb_check_var(), it means it cannot
change video mode. Hence this rules out #1.

#2 is not acceptable, as it will break existing applications. It's also
incorrect, as FBIOPUT_VSCREENINFO should succeed for supported modes.
For unsupported modes, the mode should be rounded up to a supported mode, if
possible. In the case of drivers that support one fixed mode only, this
rounding up is relaxed to `rounding' to the sole supported mode.

#3 is also wrong, as fb_check_var() has been deliberately made optional to
simplify drivers that support one fixed mode only.

Conclusion: nothing should be changed?

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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