Hi Sakari, On Saturday 01 September 2012 12:57:07 Sakari Ailus wrote: > On Wed, Aug 29, 2012 at 08:11:50PM +0530, Prabhakar Lad wrote: [snip] > > For test pattern you meant control to enable/disable it ? > > There are two approaches I can think of. > > One is a menu control which can be used to choose the test pattern (or > disable it). The control could be standardised but the menu items would have > to be hardware-specific since the test patterns themselves are not > standardised. Agreed. The test patterns themselves are highly hardware-specific. >From personal experience with sensors, most devices implement a small, fixed set of test patterns that can be exposed through a menu control. However, some devices also implement more "configurable" test patterns. For instance the MT9V032 can generate horizontal, vertical or diagonal test patterns, or a uniform grey test pattern with a user-configurable value. This would then require two controls. > The alternative is to have a boolean control to enable (and disable) the > test pattern and then a menu control to choose which one to use. Using or > implemeting the control to select the test pattern isn't even strictly > necessary to get a test pattern out of the device: one can enable it without > knowing which one it is. > > So which one would be better? Similar cases include V4L2_CID_SCENE_MODE > which is used to choose the scene mode from a list of alternatives. The main > difference to this case is that the menu items of the scene mode control > are standardised, too. > > I'd be inclined to have a single menu control, even if the other menu items > will be device-specific. The first value (0) still has to be documented to > mean the test pattern is disabled. > > Laurent, Hans: what do you think? A menu control with value 0 meaning test pattern disabled has my preference as well. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
