Re: [PATCH] Do set var even if no fb_check_var() provided.
flat view
From: Ville Syrjälä <syrjala@sci.fi>
Date: 2008-08-28 07:45:30
On Wed, Aug 27, 2008 at 11:49:15PM +0200, Helge Deller wrote:
Geert Uytterhoeven wrote:quoted
On Wed, 27 Aug 2008, Takashi Yoshii wrote:quoted
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?I'm not sure. On parisc we just stumbled over exactly this problem where I think Takashi's proposal "1." is probably the right solution.
What about this? 4. Provide a generic check_var() that does some basic sanity checking against info->var (eg. check xres, yres and bits_per_pixel). -- Ville Syrjälä syrjala@sci.fi http://www.sci.fi/~syrjala/ ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/