From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF6854C87 for ; Wed, 21 Feb 2024 10:40:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708512039; cv=none; b=uLJmhnxecjS/YA1z2mcbQGJ0wDsZiMf0rKi25ClEn4L/3tIE+gHANhrjFC6qAKbudT5/t+Xv1Xh/D11tZXVB3A6++jMDGxTNZ2ayKNxycFs9fJ0FMfOKn2XAwLFRD4HN8mm1dNqwzqxkrMDKR0mZSUwP7fcplakeXUnJpb04bcI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708512039; c=relaxed/simple; bh=rhdmYaBh65YHIrcDvPBnqAPlqWFGCggwa9Kpz+k2r9c=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=J5Pm+QW47L299GK1W/DFU9Z3HXXCy5ZGtW7kgW8+nmKS6uJOUyxFCbIZ6w6uRTVUqxNXD9L1e0HynD8p1aQVkjl8wsBbjetOTP1CjWg5XCud+iqjzGu/9PDluwWJOsYecFhiOnWXGjFQH12De7pHjCTs3+1KQl7S/iZfdTCtE7M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=NFL5o0MJ; arc=none smtp.client-ip=192.198.163.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="NFL5o0MJ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1708512038; x=1740048038; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=rhdmYaBh65YHIrcDvPBnqAPlqWFGCggwa9Kpz+k2r9c=; b=NFL5o0MJ+LVcbWgy9+Ye/01AYmRJJM9pYGXREfX0iXjnreaNaNbaq42D sQ2ppEZp1t0zTGWzA+IbppFod0B3HACYCTqc7iYbkbs80lcl5c6MHrNoX 5SiYxavXmBmikHaLrasNKSF/8IESfBSUer7btDgNscBYb0uB3o1jL7Fib asNnMAmFXXebiTKwt54lkTxvEFOhElBMUsuVIuVoLtlkoq6PNy2Y6Gbnt iQ2R5ItYqOHFkTKdsQDvrKRzKXzfZe4APcIG3fhPb5ywrk7CyDCH11t2m uCr07ihsJnPbo/6KeDVChAafrrkSZ0xDVmb6ZGOwMHpIx7EDXgMHCut1T g==; X-IronPort-AV: E=McAfee;i="6600,9927,10990"; a="3143339" X-IronPort-AV: E=Sophos;i="6.06,175,1705392000"; d="scan'208";a="3143339" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Feb 2024 02:40:37 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10990"; a="936623102" X-IronPort-AV: E=Sophos;i="6.06,175,1705392000"; d="scan'208";a="936623102" Received: from turnipsi.fi.intel.com (HELO kekkonen.fi.intel.com) ([10.237.72.44]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Feb 2024 02:40:36 -0800 Received: from kekkonen.localdomain (localhost [127.0.0.1]) by kekkonen.fi.intel.com (Postfix) with SMTP id 8C0BC11F855; Wed, 21 Feb 2024 12:40:33 +0200 (EET) Date: Wed, 21 Feb 2024 10:40:33 +0000 From: Sakari Ailus To: Hans Verkuil Cc: linux-media@vger.kernel.org, laurent.pinchart@ideasonboard.com Subject: Re: [PATCH v2 17/29] media: v4l: Acquire a reference to the media device for every video device Message-ID: References: <20231220103713.113386-1-sakari.ailus@linux.intel.com> <20231220103713.113386-18-sakari.ailus@linux.intel.com> <2708ec26-3156-4269-85ae-d9e783dc3bd1@xs4all.nl> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2708ec26-3156-4269-85ae-d9e783dc3bd1@xs4all.nl> Hi Hans, Many thanks for reviewing these. On Mon, Feb 05, 2024 at 03:56:22PM +0100, Hans Verkuil wrote: > On 20/12/2023 11:37, Sakari Ailus wrote: > > The video device depends on the existence of its media device --- if there > > is one. Acquire a reference to it. > > > > Note that when the media device release callback is used, then the V4L2 > > device release callback is ignored and a warning is issued if both are > > set. > > > > Signed-off-by: Sakari Ailus > > --- > > drivers/media/v4l2-core/v4l2-dev.c | 51 ++++++++++++++++++++---------- > > 1 file changed, 34 insertions(+), 17 deletions(-) > > > > diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c > > index d13954bd31fd..c1e4995eaf5c 100644 > > --- a/drivers/media/v4l2-core/v4l2-dev.c > > +++ b/drivers/media/v4l2-core/v4l2-dev.c > > @@ -176,6 +176,11 @@ static void v4l2_device_release(struct device *cd) > > { > > struct video_device *vdev = to_video_device(cd); > > struct v4l2_device *v4l2_dev = vdev->v4l2_dev; > > + bool v4l2_dev_has_release = v4l2_dev->release; > > +#ifdef CONFIG_MEDIA_CONTROLLER > > + struct media_device *mdev = v4l2_dev->mdev; > > + bool mdev_has_release = mdev && mdev->ops && mdev->ops->release; > > +#endif > > > > mutex_lock(&videodev_lock); > > if (WARN_ON(video_devices[vdev->minor] != vdev)) { > > @@ -198,8 +203,8 @@ static void v4l2_device_release(struct device *cd) > > > > mutex_unlock(&videodev_lock); > > > > -#if defined(CONFIG_MEDIA_CONTROLLER) > > - if (v4l2_dev->mdev && vdev->vfl_dir != VFL_DIR_M2M) { > > +#ifdef CONFIG_MEDIA_CONTROLLER > > + if (mdev && vdev->vfl_dir != VFL_DIR_M2M) { > > /* Remove interfaces and interface links */ > > media_devnode_remove(vdev->intf_devnode); > > if (vdev->entity.function != MEDIA_ENT_F_UNKNOWN) > > @@ -207,23 +212,31 @@ static void v4l2_device_release(struct device *cd) > > } > > #endif > > > > - /* Do not call v4l2_device_put if there is no release callback set. > > - * Drivers that have no v4l2_device release callback might free the > > - * v4l2_dev instance in the video_device release callback below, so we > > - * must perform this check here. > > - * > > - * TODO: In the long run all drivers that use v4l2_device should use the > > - * v4l2_device release callback. This check will then be unnecessary. > > - */ > > - if (v4l2_dev->release == NULL) > > - v4l2_dev = NULL; > > - > > /* Release video_device and perform other > > cleanups as needed. */ > > vdev->release(vdev); > > > > - /* Decrease v4l2_device refcount */ > > - if (v4l2_dev) > > +#ifdef CONFIG_MEDIA_CONTROLLER > > + if (mdev) > > + media_device_put(mdev); > > + > > + /* > > + * Generally both struct media_device and struct v4l2_device are > > + * embedded in the same driver's context struct so having a release > > + * callback in both is a bug. > > + */ > > + WARN_ON(v4l2_dev_has_release && mdev_has_release); > > How about: > > if (WARN_ON(v4l2_dev_has_release && mdev_has_release)) > v4l2_dev_has_release = false; > > > +#endif > > + > > + /* > > + * Decrease v4l2_device refcount, but only if the media device doesn't > > + * have a release callback. > > + */ > > + if (v4l2_dev_has_release > > +#ifdef CONFIG_MEDIA_CONTROLLER > > + && !mdev_has_release > > +#endif > > + ) > > Then this change is no longer needed. Good idea. I'll also rename v4l2_dev_has_release as v4l2_dev_call_release. > > General question: do we have drivers today that set both release functions? > Because that would now cause a WARN in the kernel log with this patch. Indeed, the intention is to be vocal about it. The only user of the v4l2_device release function I could find is drivers/media/radio/dsbr100.c . I may have missed some but it certainly isn't commonly used. Maybe we could try to drop refcounting from v4l2_device later on? > > > v4l2_device_put(v4l2_dev); > > } > > > > @@ -792,11 +805,14 @@ static int video_register_media_controller(struct video_device *vdev) > > u32 intf_type; > > int ret; > > > > - /* Memory-to-memory devices are more complex and use > > + /* > > + * Memory-to-memory devices are more complex and use > > * their own function to register its mc entities. > > */ > > - if (!vdev->v4l2_dev->mdev || vdev->vfl_dir == VFL_DIR_M2M) > > + if (!vdev->v4l2_dev->mdev || vdev->vfl_dir == VFL_DIR_M2M) { > > + media_device_get(vdev->v4l2_dev->mdev); > > return 0; > > + } > > > > vdev->entity.obj_type = MEDIA_ENTITY_TYPE_VIDEO_DEVICE; > > vdev->entity.function = MEDIA_ENT_F_UNKNOWN; > > @@ -875,6 +891,7 @@ static int video_register_media_controller(struct video_device *vdev) > > > > /* FIXME: how to create the other interface links? */ > > > > + media_device_get(vdev->v4l2_dev->mdev); > > #endif > > return 0; > > } -- Kind regards, Sakari Ailus