From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Date: Fri, 12 Aug 2011 11:08:59 +0000 Subject: How should .fb_check_var adjust parameters ? Message-Id: <201108121308.59532.laurent.pinchart@ideasonboard.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-fbdev@vger.kernel.org Hi everybody, I'm implementing support for fb_set_par() in a driver, and came to think about how fb_check_var should behave. The purpose of that operation is to let drivers verify and adjust a given set of fb_var_screeninfo parameters. Looking at various fbdev drivers, the function behaviour is clearly left to the author's preferences. Some drivers return an error when the parameters don't match the hardware capabilities exactly, other drivers adjust them in pretty much non-standardized ways, and some other drivers mix both behaviours. Is anyone aware of guidelines regarding how .fb_char_var should be implemented ? Under which conditions should it return an error, and under which conditions should it adjust parameters ? When adjusting parameters, how should it do so ? For instance, if xres > xres_virtual, should xres be lowered or xres_virtual raised ? -- Regards, Laurent Pinchart