Em Sat, 29 Apr 2017 00:00:05 +0200 Pavel Machek <pavel@xxxxxx> escreveu: > Hi! > > > Hmm... if the idea is to have a control that doesn't do ringing > > compensation, then it should be clear at the control's descriptions > > that: > > > > - V4L2_CID_FOCUS_ABSOLUTE should be used if the VCM has ringing > > compensation; > > - V4L2_CID_VOICE_COIL_CURRENT and V4L2_CID_VOICE_COIL_RING_COMPENSATION > > should be used otherwise. > > > > Btw, if the rationale for this patch is to support devices without > > ring compensation, so, both controls and their descriptions should > > be added at the same time, together with a patchset that would be > > using both. > > > > > How about adding such an explanation added to the commit message? > > > > It is not enough. Documentation should be clear that VCM devices > > with ring compensation should use V4L2_CID_FOCUS_ABSOLUTE. > > Is ring compensation actually a big deal? We do not publish enough > information to userland about how fast the autofocus system is, > anyway, so it looks like userland can't depend on such details... Well, I guess a V4L2 event could be used to identify the VCM's current position and/or notify when the movement finished. Anyway, the point is: If V4L2_CID_VOICE_COIL_CURRENT would do the same as: V4L2_CID_FOCUS_ABSOLUTE or: max - V4L2_CID_FOCUS_ABSOLUTE there's no reason to create a new control, as the existing control was already created to control the VCM current [1]. [1] Ok, we need to better document it, but that's a separate issue We should create a new control only if it is doing something different than the "standard" way of controlling a Voice Coil Motor. On such case, the difference between controlling VCM via V4L2_CID_VOICE_COIL_CURRENT or via V4L2_CID_FOCUS_ABSOLUTE should be clearly stated, as we expect that the other devices with the same need will implement the same control set and the same max/min convention (e. g. max integer value meaning closest focus, min integer value meaning infinite). Thanks, Mauro
