Hi Sakari, On 03/23/2011 10:52 AM, Sakari Ailus wrote: > Hi Michael, > > Thanks for the patch. > > Michael Jones wrote: >> From dccbd4a0a717ee72a3271075b1e3456a9c67ca0e Mon Sep 17 00:00:00 2001 >> From: Michael Jones <michael.jones@xxxxxxxxxxxxxxxx> >> Date: Tue, 22 Mar 2011 11:47:22 +0100 >> Subject: [PATCH] omap3isp: implement ENUM_FMT >> >> Whatever format is currently being delivered will be declared as the only >> possible format >> >> Signed-off-by: Michael Jones <michael.jones@xxxxxxxxxxxxxxxx> >> --- >> >> Some V4L2 apps require ENUM_FMT, which is a mandatory ioctl for V4L2. >> This patch doesn't enumerate all of the formats which could possibly be >> set (as is intended by ENUM_FMT), but at least it reports the one that >> is currently set. > > What would be the purpose of ENUM_FMT in this case? It provides no > additional information to user space, and the information it provides is > in fact incomplete. Using other formats is possible, but that requires > changes to the format configuration on links. The only purpose of it was to provide minimum functionality for apps to be able to fetch frames from the ISP after setting up the ISP pipeline with media-ctl. By "apps", I mean Gstreamer in my case, which Loïc had also recently asked Laurent about. > > As the relevant format configuration is done on the subdevs and not on > the video nodes, the format configuration on the video nodes is very > limited and much affected by the state of the formats on the subdev pads > (which I think is right). This is not limited to ENUM_FMT but all format > related IOCTLs on the OMAP 3 ISP driver. > > My view is that should a generic application want to change (or > enumerate) the format(s) on a video node, the application would need to > be using libv4l for that. > > A compatibility layer implemented in libv4l (plugin, not the main > library) needs to configure the links in the first place, so > implementing ENUM_FMT in the plugin would not be a big deal. It could > even provide useful information. The possible results of the ENUM_FMT > would also depend on what kind of pipeline configuration does the plugin > support, though. BTW, my GStreamer is using libv4l, although it looked like it's also possible to configure GStreamer to use ioctls directly. I can agree that it would be nice to implement ENUM_FMT and the like in a compatibility layer in libv4l. That would be in the true spirit of ENUM_FMT, where the app could actually see different formats it can set. But is there any work being done on such a compatibility layer? Is there a policy decision that in the future, apps will be required to use libv4l to get images from the ISP? Are we not intending to support using e.g. media-ctl + some v4l2 app, as I'm currently doing during development? In the meantime, I will continue using this patch locally to enable getting a live image with Gstreamer, and it can at least serve as a help to Loïc if he's trying to do the same. > > (Cc Yordan and Hans.) > > I discussed this with Laurent initially and the conclusion was that more > discussion is required. :-) Hans: do you have an opinion on this? > > Best regards, > thanks for the discussion, Michael MATRIX VISION GmbH, Talstrasse 16, DE-71570 Oppenweiler Registergericht: Amtsgericht Stuttgart, HRB 271090 Geschaeftsfuehrer: Gerhard Thullner, Werner Armingeon, Uwe Furtner -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
