From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08EEAC10F1B for ; Wed, 21 Dec 2022 22:21:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234805AbiLUWV3 (ORCPT ); Wed, 21 Dec 2022 17:21:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35348 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229968AbiLUWVZ (ORCPT ); Wed, 21 Dec 2022 17:21:25 -0500 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A11C627145; Wed, 21 Dec 2022 14:21:23 -0800 (PST) Received: from pendragon.ideasonboard.com (213-243-189-158.bb.dnainternet.fi [213.243.189.158]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 1EF9CFB; Wed, 21 Dec 2022 23:21:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1671661281; bh=lyvNIEhEvmk5FHolnG9uYXcz/YyY1A5Se++FwfI3/aE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f1HIE3/4uli18oQNQS/zZNQOJ6coxf5ajW8MFtZ5Jxy2GDxmMukame3LFxU9W+dRn Tc8r8EJgAf/ptgdAJOAmTBd+FocIGbydGs9mE4BEbt3jfGlescf0bAHNGEcaB6I2fd rHN+ANfvROR8Coqw492xK9eEREA6FSMtonY2A4FE= Date: Thu, 22 Dec 2022 00:21:16 +0200 From: Laurent Pinchart To: Mauro Carvalho Chehab Cc: Ricardo Ribalda , Yunke Cao , Sergey Senozhatsky , linux-media@vger.kernel.org, Mauro Carvalho Chehab , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/3] media: v4l2-dev.c: Add Meta: to the name of metadata devices Message-ID: References: <20220920-resend-meta-v4-0-3ac355b66723@chromium.org> <20220920-resend-meta-v4-1-3ac355b66723@chromium.org> <20221221221601.1636c763@sal.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221221221601.1636c763@sal.lan> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mauro, On Wed, Dec 21, 2022 at 10:16:01PM +0000, Mauro Carvalho Chehab wrote: > Em Fri, 02 Dec 2022 18:08:17 +0100 Ricardo Ribalda escreveu: > > > Devices with Metadata output (like uvc), create two video devices, one > > for the data itself and another one for the metadata. > > > > Add a "Meta: " to the beginning of the device name, as suggested by Mauro, > > to avoid having multiple devices with the same name. > > Hmm... I don't remember when I suggested it, but I suspect that such > change could cause regressions on userspace. > > I double-checked: the two apps I know that have code to detect meta > devices (Camorama and ZBar) won't be affected by name changes, as they > always open v4l2 devnodes before start seeing them as capture devices, > and run VIDIOC_QUERYCAP to check for V4L2_CAP_VIDEO_CAPTURE: > > if (first_device < 0) { > fd = open(file, O_RDWR); > if (fd < 0) { > devices[n_devices].is_valid = FALSE; > } else { > if (ioctl(fd, VIDIOC_QUERYCAP, &vid_cap) == -1) { > devices[n_devices].is_valid = FALSE; > } else if (!(vid_cap.device_caps & V4L2_CAP_VIDEO_CAPTURE)) { > devices[n_devices].is_valid = FALSE; > } else { > n_valid_devices++; > devices[n_devices].is_valid = TRUE; > } > } > > close(fd); > } else { > devices[n_devices].is_valid = devices[first_device].is_valid; > } > > You need to double-check if this won't cause userspace regressions, specially > on browsers, as they have more complex logic, and seem to have already some > logic to detect and remove meta files. As commented separately in the same mail thread, this change would break libcamera. For drivers that have well-known names for entities, we look up some entities by name. For the uvcvideo driver, which is affected by the v4l2-compliance failure, a prefix (or suffix, or anything else) would be fine, but we can't do that unconditionally for all devices. > > Fixes v4l2-compliance: > > Media Controller ioctls: > > fail: v4l2-test-media.cpp(205): v2_entity_names_set.find(key) != v2_entity_names_set.end() > > test MEDIA_IOC_G_TOPOLOGY: FAIL > > fail: v4l2-test-media.cpp(394): num_data_links != num_links > > test MEDIA_IOC_ENUM_ENTITIES/LINKS: FAIL > > > > Suggested-by: Mauro Carvalho Chehab > > Signed-off-by: Ricardo Ribalda > > --- > > drivers/media/v4l2-core/v4l2-dev.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c > > index 397d553177fa..5c2c9ebb6b96 100644 > > --- a/drivers/media/v4l2-core/v4l2-dev.c > > +++ b/drivers/media/v4l2-core/v4l2-dev.c > > @@ -901,6 +901,15 @@ int __video_register_device(struct video_device *vdev, > > if (WARN_ON(type != VFL_TYPE_SUBDEV && !vdev->device_caps)) > > return -EINVAL; > > > > + /* Add Meta: to metadata device names */ > > + if (vdev->device_caps & > > + (V4L2_CAP_META_CAPTURE | V4L2_CAP_META_OUTPUT)) { > > + char aux[sizeof(vdev->name)]; > > + > > + snprintf(aux, sizeof(aux), "Meta: %s", vdev->name); > > + strscpy(vdev->name, aux, sizeof(aux)); > > + } > > + > > /* v4l2_fh support */ > > spin_lock_init(&vdev->fh_lock); > > INIT_LIST_HEAD(&vdev->fh_list); -- Regards, Laurent Pinchart