From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.ripard@free-electrons.com (Maxime Ripard) Date: Thu, 4 Jan 2018 15:06:25 +0100 Subject: [linux-sunxi] [PATCH v4 0/2] Initial Allwinner V3s CSI Support In-Reply-To: <20171225085802.lfyk4blmbqxq6r2m@core.my.home> References: <1513935138-35223-1-git-send-email-yong.deng@magewell.com> <1513950408.841.81.camel@megous.com> <20171225111526.4663f997f5d6bfc6cf157f10@magewell.com> <20171225085802.lfyk4blmbqxq6r2m@core.my.home> Message-ID: <20180104140625.5gbeaj5vgetusjlf@flea.lan> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Dec 25, 2017 at 09:58:02AM +0100, Ond?ej Jirman wrote: > Hello, > > On Mon, Dec 25, 2017 at 11:15:26AM +0800, Yong wrote: > > Hi, > > > > On Fri, 22 Dec 2017 14:46:48 +0100 > > Ond?ej Jirman wrote: > > > > > Hello, > > > > > > Yong Deng p??e v P? 22. 12. 2017 v 17:32 +0800: > > > > > > > > Test input 0: > > > > > > > > Control ioctls: > > > > test VIDIOC_QUERY_EXT_CTRL/QUERYMENU: OK (Not Supported) > > > > test VIDIOC_QUERYCTRL: OK (Not Supported) > > > > test VIDIOC_G/S_CTRL: OK (Not Supported) > > > > test VIDIOC_G/S/TRY_EXT_CTRLS: OK (Not Supported) > > > > test VIDIOC_(UN)SUBSCRIBE_EVENT/DQEVENT: OK (Not Supported) > > > > test VIDIOC_G/S_JPEGCOMP: OK (Not Supported) > > > > Standard Controls: 0 Private Controls: 0 > > > > > > I'm not sure if your driver passes control queries to the subdev. It > > > did not originally, and I'm not sure you picked up the change from my > > > version of the driver. "Not supported" here seems to indicate that it > > > does not. > > > > > > I'd be interested what's the recommended practice here. It sure helps > > > with some apps that expect to be able to modify various input controls > > > directly on the /dev/video# device. These are then supported out of the > > > box. > > > > > > It's a one-line change. See: > > > > > > https://www.kernel.org/doc/html/latest/media/kapi/v4l2-controls.html#in > > > heriting-controls > > > > I think this is a feature and not affect the driver's main function. > > I just focused on making the CSI main function to work properly in > > the initial version. Is this feature mandatory or most commonly used? > > I grepped the platform/ code and it seems, that inheriting controls > from subdevs is pretty common for input drivers. (there are varying > approaches though, some inherit by hand in the link function, some > just register and empty ctrl_handler on the v4l2_dev and leave the > rest to the core). > > Practically, I haven't found a common app that would allow me to enter > both /dev/video0 and /dev/v4l-subdevX. I'm sure anyone can write one > themselves, but it would be better if current controls were available > at the /dev/video0 device automatically. > > It's much simpler for the userspace apps than the alternative, which > is trying to identify the correct subdev that is currently > associated with the CSI driver at runtime, which is not exactly > straightforward and requires much more code, than a few lines in > the kernel, that are required to inherit controls: And it becomes much more complicated once you have the same controls on the v4l2 device and subdevice, which is not that uncommon. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: