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Message-ID: <20150911060728.0d8c061d@recife.lan> Date: Fri, 11 Sep 2015 06:07:28 -0300 From: Mauro Carvalho Chehab <mchehab@....samsung.com> To: Javier Martinez Canillas <javier@....samsung.com> Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>, linux-kernel@...r.kernel.org, Luis de Bethencourt <luis@...ethencourt.com>, linux-sh@...r.kernel.org, Sylwester Nawrocki <s.nawrocki@...sung.com>, Sören Brinkmann <soren.brinkmann@...inx.com>, linux-samsung-soc@...r.kernel.org, Hyun Kwon <hyun.kwon@...inx.com>, Matthias Schwarzott <zzam@...too.org>, Kyungmin Park <kyungmin.park@...sung.com>, Tommi Rantala <tt.rantala@...il.com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>, Hans Verkuil <hans.verkuil@...co.com>, linux-media@...r.kernel.org, Kukjin Kim <kgene@...nel.org>, Krzysztof Kozlowski <k.kozlowski@...sung.com>, Michal Simek <michal.simek@...inx.com>, Olli Salonen <olli.salonen@....fi>, linux-arm-kernel@...ts.infradead.org, Stefan Richter <stefanr@...6.in-berlin.de>, Antti Palosaari <crope@....fi>, Shuah Khan <shuahkh@....samsung.com>, Rafael Lourenço de Lima Chehab <chehabrafael@...il.com> Subject: Re: [PATCH 2/2] [media] media-device: split media initialization and registration Em Fri, 11 Sep 2015 09:31:36 +0200 Javier Martinez Canillas <javier@....samsung.com> escreveu: > Hello Sakari, > > On 09/11/2015 07:51 AM, Sakari Ailus wrote: > > Hi Javier, > > > > Javier Martinez Canillas wrote: > >> Hello Sakari, > >> > >> On 09/10/2015 07:14 PM, Sakari Ailus wrote: > >>> Hi Javier, > >>> > >>> Thanks for the set! A few comments below. > >>> > >> > >> Thanks to you for your feedback. > >> > >>> Javier Martinez Canillas wrote: > >>>> The media device node is registered and so made visible to user-space > >>>> before entities are registered and links created which means that the > >>>> media graph obtained by user-space could be only partially enumerated > >>>> if that happens too early before all the graph has been created. > >>>> > >>>> To avoid this race condition, split the media init and registration > >>>> in separate functions and only register the media device node when > >>>> all the pending subdevices have been registered, either explicitly > >>>> by the driver or asynchronously using v4l2_async_register_subdev(). > >>>> > >>>> Also, add a media_entity_cleanup() function that will destroy the > >>>> graph_mutex that is initialized in media_entity_init(). > >>>> > >>>> Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com> > >>>> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com> > >>>> > >>>> --- > >>>> > >>>> drivers/media/common/siano/smsdvb-main.c | 1 + > >>>> drivers/media/media-device.c | 38 +++++++++++++++++++++++---- > >>>> drivers/media/platform/exynos4-is/media-dev.c | 12 ++++++--- > >>>> drivers/media/platform/omap3isp/isp.c | 11 +++++--- > >>>> drivers/media/platform/s3c-camif/camif-core.c | 13 ++++++--- > >>>> drivers/media/platform/vsp1/vsp1_drv.c | 19 ++++++++++---- > >>>> drivers/media/platform/xilinx/xilinx-vipp.c | 11 +++++--- > >>>> drivers/media/usb/au0828/au0828-core.c | 26 +++++++++++++----- > >>>> drivers/media/usb/cx231xx/cx231xx-cards.c | 22 +++++++++++----- > >>>> drivers/media/usb/dvb-usb-v2/dvb_usb_core.c | 11 +++++--- > >>>> drivers/media/usb/dvb-usb/dvb-usb-dvb.c | 13 ++++++--- > >>>> drivers/media/usb/siano/smsusb.c | 14 ++++++++-- > >>>> drivers/media/usb/uvc/uvc_driver.c | 9 +++++-- > >>>> include/media/media-device.h | 2 ++ > >>>> 14 files changed, 156 insertions(+), 46 deletions(-) > >>>> > >>>> diff --git a/drivers/media/common/siano/smsdvb-main.c b/drivers/media/common/siano/smsdvb-main.c > >>>> index ab345490a43a..8a1ea2192439 100644 > >>>> --- a/drivers/media/common/siano/smsdvb-main.c > >>>> +++ b/drivers/media/common/siano/smsdvb-main.c > >>>> @@ -617,6 +617,7 @@ static void smsdvb_media_device_unregister(struct smsdvb_client_t *client) > >>>> if (!coredev->media_dev) > >>>> return; > >>>> media_device_unregister(coredev->media_dev); > >>>> + media_device_cleanup(coredev->media_dev); > >>>> kfree(coredev->media_dev); > >>>> coredev->media_dev = NULL; > >>>> #endif > >>>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c > >>>> index 745defb34b33..a8beb0b445a6 100644 > >>>> --- a/drivers/media/media-device.c > >>>> +++ b/drivers/media/media-device.c > >>>> @@ -526,7 +526,7 @@ static void media_device_release(struct media_devnode *mdev) > >>>> } > >>>> > >>>> /** > >>>> - * media_device_register - register a media device > >>>> + * media_device_init() - initialize a media device > >>>> * @mdev: The media device > >>>> * > >>>> * The caller is responsible for initializing the media device before > >>>> @@ -534,12 +534,11 @@ static void media_device_release(struct media_devnode *mdev) > >>>> * > >>>> * - dev must point to the parent device > >>>> * - model must be filled with the device model name > >>>> + * > >>>> + * returns zero on success or a negative error code. > >>>> */ > >>>> -int __must_check __media_device_register(struct media_device *mdev, > >>>> - struct module *owner) > >>>> +int __must_check media_device_init(struct media_device *mdev) > >>> > >>> I think I suggested making media_device_init() return void as the only > >>> remaining source of errors would be driver bugs. > >>> > >> > >> Yes you did and I think I explained why I preferred to leave it as > >> is and I thought we agreed :) > > > > I thought we agreed, too. But my understanding was that the agreement was different. ;-) > > > > Fair enough :) > > >> > >> Currently media_device_register() is failing gracefully if a buggy > >> driver is not setting mdev->dev. So changing media_device_init() to > >> return void instead, would be a semantic change and if drivers are > >> not checking that anymore, can lead to NULL pointer dereference bugs. > > > > Do we have such drivers? Would they ever have worked in the first place, as media device registration would have failed? Actually we do. The media controller is an optional feature at the DVB only drivers (dvb-usb, dvb-usb-v2, siano), as it is used only to show the interfaces associated to them, and no functionality will be lost if it fails to register the MC (except for the enumeration). I don't see any reason why making it mandatory at those PC customer DVB drivers. If it fails... well, G_TOPOLOGY won't work, but all the rest will. For hybrid devices (au0828 and cx231xx), they're currently optional. I wrote a patch already on my WIP branch making it mandatory for au0828, provided that the MEDIA_CONTROLLER config option is enabled, and I intend to do the same for cx231xx. The rationale is that we'll use it to lock between analog and digital part, so it should be mandatory there. Regards, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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