Re: [PATCH 4/4] [meida] media-device: dynamically allocate struct media_devnode

Mauro Carvalho Chehab
2016-04-28T11:42:04Z

Em Wed, 27 Apr 2016 16:20:56 -0600
Shuah Khan <shuah.kh@samsung.com> escreveu:

> On 03/24/2016 05:37 AM, Mauro Carvalho Chehab wrote:
> > Em Thu, 24 Mar 2016 10:24:44 +0200
> > Laurent Pinchart <laurent.pinchart@ideasonboard.com> escreveu:
> >
> >> On Wednesday 23 Mar 2016 16:27:46 Mauro Carvalho Chehab wrote:
> >>> struct media_devnode is currently embedded at struct media_device.
> >>>
> >>> While this works fine during normal usage, it leads to a race
> >>> condition during devnode unregister. the problem is that drivers
> >>> assume that, after calling media_device_unregister(), the struct
> >>> that contains media_device can be freed. This is not true, as it
> >>> can't be freed until userspace closes all opened /dev/media devnodes.
> >>>
> >>> In other words, if the media devnode is still open, and media_device
> >>> gets freed, any call to an ioctl will make the core to try to access
> >>> struct media_device, with will cause an use-after-free and even GPF.
> >>>
> >>> Fix this by dynamically allocating the struct media_devnode and only
> >>> freeing it when it is safe.
>
> Hi Mauro,
>
> I think this is the patch you were referring to in response to the patch
> I sent out. Looks like this is still under review and some outstanding
> issues. This patch itself doesn't ensure media_devnode sticks around
> until the last app. closes the cdev. More work is needed such as adding
> cdev parent and providing kobject release function that can be called
> from cdev-core which will free media_devnode when the last cdev ref
> is gone.
>
> Anyway, since you asked me to do the fix on top of your patch, I am asking
> to see if this patch is in a good shape for me to apply. As such, we no
> longer have sound/us/media.c in the mix. Hence this patch needs work before
> I can base my work on it.

Well, the only issue on it is that it needed to be rebased on the top of
the current tree. I did such rebase for you, at:
https://git.linuxtv.org/mchehab/experimental.git/log/?h=au0828-unbind-fixes-v5

As said before, it doesn't touch cdev, nor adds any kref.

I'm running it today with the stress test. So far (~100 unbind loops, with 5
concurrent accesses via mc_nextgen_test), the only issue it got so
far seems to be at V4L2 cdev stuff (not at the media side, but at the
V4L2 API side):

[ 445.428212] kasan: CONFIG_KASAN_INLINE enabled
[ 445.428346] kasan: GPF could be caused by NULL-ptr deref or user memory access
[ 445.428750] general protection fault: 0000 [#2] SMP KASAN
[ 445.429417] Modules linked in: ir_lirc_codec lirc_dev au8522_dig xc5000 tuner au8522_decoder au8522_common au0828 videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core tveeprom dvb_core rc_core v4l2_common videodev media cpufreq_powersave cpufreq_conservative cpufreq_userspace cpufreq_stats parport_pc ppdev lp parport snd_hda_codec_hdmi intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm iTCO_wdt iTCO_vendor_support irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel i915 snd_hda_codec_realtek snd_hda_codec_generic sha256_ssse3 sha256_generic hmac drbg btusb btrtl btbcm aesni_intel evdev snd_hda_intel aes_x86_64 lrw btintel i2c_algo_bit snd_hda_codec gf128mul bluetooth glue_helper drm_kms_helper snd_hwdep ablk_helper cryptd snd_hda_core drm serio_raw
[ 445.431431] rfkill sg snd_pcm pcspkr snd_timer mei_me snd mei lpc_ich i2c_i801 mfd_core soundcore battery dw_dmac video dw_dmac_core i2c_designware_platform i2c_designware_core acpi_pad button tpm_tis tpm ext4 crc16 jbd2 mbcache dm_mod sd_mod ahci libahci psmouse libata e1000e ehci_pci xhci_pci ptp scsi_mod ehci_hcd pps_core xhci_hcd fan thermal sdhci_acpi sdhci mmc_core i2c_hid hid
[ 445.431907] CPU: 0 PID: 32248 Comm: v4l_id Tainted: G D 4.6.0-rc2+ #68
[ 445.431984] Hardware name: /NUC5i7RYB, BIOS RYBDWi35.86A.0350.2015.0812.1722 08/12/2015
[ 445.436336] task: ffff8803bde0b000 ti: ffff8803a22d8000 task.ti: ffff8803a22d8000
[ 445.440571] RIP: 0010:[<ffffffff81d77a61>] [<ffffffff81d77a61>] usb_ifnum_to_if+0x31/0x270
[ 445.444745] RSP: 0018:ffff8803a22df8d0 EFLAGS: 00010282
[ 445.448765] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 1ffff10074699c5e
[ 445.452648] RDX: 000000000000009e RSI: 0000000000000000 RDI: 00000000000004f0
[ 445.456339] RBP: ffff8803a22df908 R08: 0000000000000001 R09: 0000000000000001
[ 445.459885] R10: ffff8803a2254580 R11: 0000000000000000 R12: ffffffffa12be0c0
[ 445.463473] R13: ffff8803a34ceb3c R14: ffff8803a34cc080 R15: ffffffffa12a89b0
[ 445.466938] FS: 00007f4629888700(0000) GS:ffff8803c6800000(0000) knlGS:0000000000000000
[ 445.470457] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 445.473960] CR2: 00007f0e00d19000 CR3: 00000003b0bca000 CR4: 00000000003406f0
[ 445.477441] Stack:
[ 445.480959] ffff8803a3480ba0 ffff8803a34ce2f0 ffff8803a34cc000 ffffffffa12be0c0
[ 445.484563] ffff8803a34ceb3c ffff8803a34cc080 ffffffffa12a89b0 ffff8803a22df940
[ 445.488178] ffffffffa12a4a45 ffff8803a22df940 ffff8803a34cc000 0000000000000000
[ 445.491780] Call Trace:
[ 445.495317] [<ffffffffa12a89b0>] ? au0828_v4l2_close+0x5a0/0x5a0 [au0828]
[ 445.498886] [<ffffffffa12a4a45>] au0828_analog_stream_enable+0x85/0x330 [au0828]
[ 445.502461] [<ffffffffa12a8b11>] au0828_v4l2_open+0x161/0x350 [au0828]
[ 445.506012] [<ffffffffa12a89b0>] ? au0828_v4l2_close+0x5a0/0x5a0 [au0828]
[ 445.509531] [<ffffffffa1169561>] v4l2_open+0x1d1/0x350 [videodev]
[ 445.513097] [<ffffffff815cc071>] chrdev_open+0x1f1/0x580
[ 445.516643] [<ffffffff815cbe80>] ? cdev_put+0x50/0x50
[ 445.520129] [<ffffffff815b98a7>] do_dentry_open+0x5d7/0xac0
[ 445.523582] [<ffffffff815cbe80>] ? cdev_put+0x50/0x50
[ 445.526994] [<ffffffff815bc05b>] vfs_open+0x16b/0x1e0
[ 445.530442] [<ffffffff815e1c0b>] ? may_open+0x14b/0x260
[ 445.533882] [<ffffffff815eb3f7>] path_openat+0x4f7/0x3a00
[ 445.537253] [<ffffffff8156cc95>] ? alloc_debug_processing+0x75/0x1c0
[ 445.540731] [<ffffffff815eaf00>] ? vfs_create+0x390/0x390
[ 445.544198] [<ffffffff811ad88e>] ? __kernel_text_address+0x7e/0xa0
[ 445.547650] [<ffffffff8109154f>] ? print_context_stack+0x7f/0xf0
[ 445.551089] [<ffffffff8124b110>] ? debug_check_no_locks_freed+0x290/0x290
[ 445.554512] [<ffffffff815b105b>] ? create_object+0x3eb/0x940
[ 445.558004] [<ffffffff8124a5f6>] ? trace_hardirqs_on_caller+0x16/0x590
[ 445.561511] [<ffffffff815f1cd5>] do_filp_open+0x175/0x230
[ 445.565031] [<ffffffff815f1b60>] ? user_path_mountpoint_at+0x40/0x40
[ 445.568540] [<ffffffff822d8567>] ? _raw_spin_unlock+0x27/0x40
[ 445.572056] [<ffffffff81615b1a>] ? __alloc_fd+0x19a/0x4b0
[ 445.575491] [<ffffffff8156d653>] ? kmem_cache_alloc+0x233/0x300
[ 445.579023] [<ffffffff815bc615>] do_sys_open+0x195/0x340
[ 445.582510] [<ffffffff8123eb5f>] ? up_read+0x1f/0x40
[ 445.585079] [<ffffffff815bc480>] ? filp_open+0x60/0x60
[ 445.588457] [<ffffffff81242681>] ? trace_hardirqs_off_caller+0x21/0x290
[ 445.591960] [<ffffffff8100401b>] ? trace_hardirqs_on_thunk+0x1b/0x1d
[ 445.595413] [<ffffffff815bc7de>] SyS_open+0x1e/0x20
[ 445.598904] [<ffffffff822d8dc0>] entry_SYSCALL_64_fastpath+0x23/0xc1
[ 445.602394] [<ffffffff81242681>] ? trace_hardirqs_off_caller+0x21/0x290
[ 445.605902] Code: 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 57 41 56 41 55 41 54 53 48 89 fb 48 81 c7 f0 04 00 00 48 89 fa 48 c1 ea 03 48 83 ec 10 <80> 3c 02 00 0f 85 c6 01 00 00 4c 8b bb f0 04 00 00 4d 85 ff 0f
[ 445.609826] RIP [<ffffffff81d77a61>] usb_ifnum_to_if+0x31/0x270
[ 445.613516] RSP <ffff8803a22df8d0>
[ 445.617247] ---[ end trace 9127ab975e0f4104 ]---

I got two of those errors already.

> Lars gave a few comments on the patch I sent out in the code that makes
> devnode dynamic which are relevant to be folded into your patch. Added
> Lars to this thread.

Yeah, I saw Lars comments. I'll answer to his emails in a few.

>
> P.S: removed alsa folks and alsa list and added linux-media
>
> thanks,
> -- Shuah
> >>
> >> We have the exact same issue with video_device, and there we've solved the
> >> problem by passing the release call all the way up to the driver. I'm open to
> >> discuss what the best solution is, but I don't think we should special-case
> >> media_device unless there are compelling arguments regarding why different
> >> solutions are needed for media_device and video_device.
> >
> > The relationship between a video driver and video_device/v4l2_dev is
> > different. On V4L2 we have:
> > - One driver using video_device resources;
> > - multiple video_device devnodes.
> >
> > For media devices, the relationship is the opposite:
> > - multiple independent drivers using media_devnode.
> > - One media device node;
> >
> > On media devices, when multiple drivers are sharing the same devnode, the
> > .probe() order can be different than the .release() order.
> >
> > So, we don't need to use the same solution as we did for video_device
> > on media controller. Actually, the V4L2 solution won't work.
> >
> > On V4L2, a video device is typically initialized with:
> >
> > video-dev->release = video_device_release;
> > err = video_register_device(video_dev,VFL_TYPE_GRABBER,
> > video_nr[dev->nr]);
> >
> > And video_device_release is simply a kfree:
> >
> > void video_device_release(struct video_device *vdev)
> > {
> > kfree(vdev);
> > }
> >
> > The caller driver may opt to use its own code to free the resources
> > instead of the core one, but it needs to free vdev in the end
> > (or some struct that embedds it).
> >
> > In the specific case of media, drivers don't need to touch or even
> > be aware of media_devnode, as the creation of the media devnode is
> > handled internally by the core. Also, there's no good reason to
> > make the caller drivers to be aware of that.
> >
> > So, the approach taken by this patch is actually simpler, as the
> > kfree() is internal to the core, and it doesn't require
> > any callbacks. This patch provides all that it is needed to make devnode
> > destroy safe.
> >
> > On the common case where one driver allocates one /dev/media devnode,
> > using the standard media_device_register()/media_device_unregister(),
> > grants that a media_devnode instance will only be freed after all uses
> > have gone, including open() descriptors. It also grants that the caller
> > can free its own resources after media_device_unregister(), because
> > media_devnode won't use media_device anymore.
> >
> > This happens because media_devnode_is_registered() will return
> > false after media_device_unregister(), and the media_ioctl logic
> > will return an error in this case:
> > __media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg,
> > long (*ioctl_func)(struct file *filp, unsigned int cmd,
> > unsigned long arg))
> > {
> > struct media_devnode *devnode = media_devnode_data(filp);
> >
> > if (!ioctl_func)
> > return -ENOTTY;
> >
> > if (!media_devnode_is_registered(devnode))
> > return -EIO;
> > /* IMHO, it should be -ENODEV here */
> >
> > return ioctl_func(filp, cmd, arg);
> > }
> >
> > all other syscalls have a similar test.
> >
> > When more than one driver shares the same media devnode - e. g. the
> > case that it is currently using media_device_*_devres(), the V4L2
> > solution of exposing the .release() callback to the caller driver
> > won't work, as the unbind order can be different than the binding
> > one. So, it is not possible to have .release() callbacks.
> >
> > On the multiple drivers scenario, a kref is used to identify when
> > all drivers called media_device_unregister_devres(). Only when the
> > last driver called it, it will do the actual media_device cleanups
> > and will wait for userspace to close all opened file descriptors,
> > calling kfree(media_devnode) only after that. It is also safe for
> > a device driver to cleanup its own resources after
> > media_device_release_devres(), as, if the driver is not the last
> > one, media_device and media_devnode will still be allocated, and,
> > if it is the last one, this will fallback on the case of a single
> > driver.
> >
> > I can't think on any other race-free solution than the one implemented
> > by this patch, and still being simple.
> >
> >> I also suspect we will need to consider dynamic pipeline management sooner
> >> than later to solve the problem properly if we don't want to create code today
> >> that will need to be completely reworked tomorrow.
> >
> > On the stress testing we're doing, we're removing/recreating part of the
> > graph, by unbinding/rebinding one one of the drivers, while keep calling
> > G_TOPOLOGY on an endless loop.
> >
> > It is working quite well. The change from semaphore->mutex, suggested
> > by Sakari seemed to solve all the locking issues we had before.
> >
> > Ok, I didn't test SETUP_LINK, but, as it is now protected by the same
> > mutex, except for some hidden bug, I guess it will work just fine.
> >
> > So, I don't see any need to change the locking schema at the core,
> > to avoid race issues.
> >
> >>
> >>> Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> >>> ---
> >>> drivers/media/media-device.c | 38 +++++++++++++++++++------------
> >>> drivers/media/media-devnode.c | 7 ++++++-
> >>> drivers/media/usb/au0828/au0828-core.c | 4 ++--
> >>> drivers/media/usb/uvc/uvc_driver.c | 2 +-
> >>> include/media/media-device.h | 5 +----
> >>> include/media/media-devnode.h | 15 ++++++++++++--
> >>> sound/usb/media.c | 8 +++----
> >>> 7 files changed, 52 insertions(+), 27 deletions(-)
> >>>
> >>> diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
> >>> index 10cc4766de10..d10dc615e7a8 100644
> >>> --- a/drivers/media/media-device.c
> >>> +++ b/drivers/media/media-device.c
> >>> @@ -428,7 +428,7 @@ static long media_device_ioctl(struct file *filp,
> >>> unsigned int cmd, unsigned long arg)
> >>> {
> >>> struct media_devnode *devnode = media_devnode_data(filp);
> >>> - struct media_device *dev = to_media_device(devnode);
> >>> + struct media_device *dev = devnode->media_dev;
> >>> long ret;
> >>>
> >>> switch (cmd) {
> >>> @@ -504,7 +504,7 @@ static long media_device_compat_ioctl(struct file *filp,
> >>> unsigned int cmd, unsigned long arg)
> >>> {
> >>> struct media_devnode *devnode = media_devnode_data(filp);
> >>> - struct media_device *dev = to_media_device(devnode);
> >>> + struct media_device *dev = devnode->media_dev;
> >>> long ret;
> >>>
> >>> switch (cmd) {
> >>> @@ -540,7 +540,8 @@ static const struct media_file_operations
> >>> media_device_fops = { static ssize_t show_model(struct device *cd,
> >>> struct device_attribute *attr, char *buf)
> >>> {
> >>> - struct media_device *mdev = to_media_device(to_media_devnode(cd));
> >>> + struct media_devnode *devnode = to_media_devnode(cd);
> >>> + struct media_device *mdev = devnode->media_dev;
> >>>
> >>> return sprintf(buf, "%.*s\n", (int)sizeof(mdev->model), mdev->model);
> >>> }
> >>> @@ -718,25 +719,36 @@ EXPORT_SYMBOL_GPL(media_device_cleanup);
> >>> int __must_check __media_device_register(struct media_device *mdev,
> >>> struct module *owner)
> >>> {
> >>> + struct media_devnode *devnode;
> >>> int ret;
> >>>
> >>> mutex_lock(&mdev->graph_mutex);
> >>>
> >>> + devnode = kzalloc(sizeof(*devnode), GFP_KERNEL);
> >>> + if (!devnode)
> >>> + return -ENOMEM;
> >>> +
> >>> /* Register the device node. */
> >>> - mdev->devnode.fops = &media_device_fops;
> >>> - mdev->devnode.parent = mdev->dev;
> >>> - mdev->devnode.release = media_device_release;
> >>> + mdev->devnode = devnode;
> >>> + devnode->fops = &media_device_fops;
> >>> + devnode->parent = mdev->dev;
> >>> + devnode->release = media_device_release;
> >>>
> >>> /* Set version 0 to indicate user-space that the graph is static */
> >>> mdev->topology_version = 0;
> >>>
> >>> - ret = media_devnode_register(&mdev->devnode, owner);
> >>> - if (ret < 0)
> >>> + ret = media_devnode_register(mdev, devnode, owner);
> >>> + if (ret < 0) {
> >>> + mdev->devnode = NULL;
> >>> + kfree(devnode);
> >>> goto err;
> >>> + }
> >>>
> >>> - ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
> >>> + ret = device_create_file(&devnode->dev, &dev_attr_model);
> >>> if (ret < 0) {
> >>> - media_devnode_unregister(&mdev->devnode);
> >>> + mdev->devnode = NULL;
> >>> + media_devnode_unregister(devnode);
> >>> + kfree(devnode);
> >>> goto err;
> >>> }
> >>>
> >>> @@ -800,9 +812,9 @@ static void __media_device_unregister(struct
> >>> media_device *mdev) }
> >>>
> >>> /* Check if mdev devnode was registered */
> >>> - if (media_devnode_is_registered(&mdev->devnode)) {
> >>> - device_remove_file(&mdev->devnode.dev, &dev_attr_model);
> >>> - media_devnode_unregister(&mdev->devnode);
> >>> + if (media_devnode_is_registered(mdev->devnode)) {
> >>> + device_remove_file(&mdev->devnode->dev, &dev_attr_model);
> >>> + media_devnode_unregister(mdev->devnode);
> >>> }
> >>>
> >>> dev_dbg(mdev->dev, "Media device unregistered\n");
> >>> diff --git a/drivers/media/media-devnode.c b/drivers/media/media-devnode.c
> >>> index ae2bc0b7a368..db47063d8801 100644
> >>> --- a/drivers/media/media-devnode.c
> >>> +++ b/drivers/media/media-devnode.c
> >>> @@ -44,6 +44,7 @@
> >>> #include <linux/uaccess.h>
> >>>
> >>> #include <media/media-devnode.h>
> >>> +#include <media/media-device.h>
> >>>
> >>> #define MEDIA_NUM_DEVICES 256
> >>> #define MEDIA_NAME "media"
> >>> @@ -74,6 +75,8 @@ static void media_devnode_release(struct device *cd)
> >>> /* Release media_devnode and perform other cleanups as needed. */
> >>> if (devnode->release)
> >>> devnode->release(devnode);
> >>> +
> >>> + kfree(devnode);
> >>> }
> >>>
> >>> static struct bus_type media_bus_type = {
> >>> @@ -218,7 +221,8 @@ static const struct file_operations media_devnode_fops =
> >>> { .llseek = no_llseek,
> >>> };
> >>>
> >>> -int __must_check media_devnode_register(struct media_devnode *devnode,
> >>> +int __must_check media_devnode_register(struct media_device *mdev,
> >>> + struct media_devnode *devnode,
> >>> struct module *owner)
> >>> {
> >>> int minor;
> >>> @@ -237,6 +241,7 @@ int __must_check media_devnode_register(struct
> >>> media_devnode *devnode, mutex_unlock(&media_devnode_lock);
> >>>
> >>> devnode->minor = minor;
> >>> + devnode->media_dev = mdev;
> >>>
> >>> /* Part 2: Initialize and register the character device */
> >>> cdev_init(&devnode->cdev, &media_devnode_fops);
> >>> diff --git a/drivers/media/usb/au0828/au0828-core.c
> >>> b/drivers/media/usb/au0828/au0828-core.c index 85c13ca5178f..598a85388d77
> >>> 100644
> >>> --- a/drivers/media/usb/au0828/au0828-core.c
> >>> +++ b/drivers/media/usb/au0828/au0828-core.c
> >>> @@ -142,7 +142,7 @@ static void au0828_unregister_media_device(struct
> >>> au0828_dev *dev) struct media_device *mdev = dev->media_dev;
> >>> struct media_entity_notify *notify, *nextp;
> >>>
> >>> - if (!mdev || !media_devnode_is_registered(&mdev->devnode))
> >>> + if (!mdev || !media_devnode_is_registered(mdev->devnode))
> >>> return;
> >>>
> >>> /* Remove au0828 entity_notify callbacks */
> >>> @@ -480,7 +480,7 @@ static int au0828_media_device_register(struct
> >>> au0828_dev *dev, if (!dev->media_dev)
> >>> return 0;
> >>>
> >>> - if (!media_devnode_is_registered(&dev->media_dev->devnode)) {
> >>> + if (!media_devnode_is_registered(dev->media_dev->devnode)) {
> >>>
> >>> /* register media device */
> >>> ret = media_device_register(dev->media_dev);
> >>> diff --git a/drivers/media/usb/uvc/uvc_driver.c
> >>> b/drivers/media/usb/uvc/uvc_driver.c index 451e84e962e2..302e284a95eb
> >>> 100644
> >>> --- a/drivers/media/usb/uvc/uvc_driver.c
> >>> +++ b/drivers/media/usb/uvc/uvc_driver.c
> >>> @@ -1674,7 +1674,7 @@ static void uvc_delete(struct uvc_device *dev)
> >>> if (dev->vdev.dev)
> >>> v4l2_device_unregister(&dev->vdev);
> >>> #ifdef CONFIG_MEDIA_CONTROLLER
> >>> - if (media_devnode_is_registered(&dev->mdev.devnode))
> >>> + if (media_devnode_is_registered(dev->mdev.devnode))
> >>> media_device_unregister(&dev->mdev);
> >>> media_device_cleanup(&dev->mdev);
> >>> #endif
> >>> diff --git a/include/media/media-device.h b/include/media/media-device.h
> >>> index e59772ed8494..b04cfa907350 100644
> >>> --- a/include/media/media-device.h
> >>> +++ b/include/media/media-device.h
> >>> @@ -347,7 +347,7 @@ struct media_entity_notify {
> >>> struct media_device {
> >>> /* dev->driver_data points to this struct. */
> >>> struct device *dev;
> >>> - struct media_devnode devnode;
> >>> + struct media_devnode *devnode;
> >>>
> >>> char model[32];
> >>> char driver_name[32];
> >>> @@ -403,9 +403,6 @@ struct usb_device;
> >>> #define MEDIA_DEV_NOTIFY_PRE_LINK_CH 0
> >>> #define MEDIA_DEV_NOTIFY_POST_LINK_CH 1
> >>>
> >>> -/* media_devnode to media_device */
> >>> -#define to_media_device(node) container_of(node, struct media_device,
> >>> devnode) -
> >>> /**
> >>> * media_entity_enum_init - Initialise an entity enumeration
> >>> *
> >>> diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h
> >>> index e1d5af077adb..cc2b3155593c 100644
> >>> --- a/include/media/media-devnode.h
> >>> +++ b/include/media/media-devnode.h
> >>> @@ -33,6 +33,8 @@
> >>> #include <linux/device.h>
> >>> #include <linux/cdev.h>
> >>>
> >>> +struct media_device;
> >>> +
> >>> /*
> >>> * Flag to mark the media_devnode struct as registered. Drivers must not
> >>> touch * this flag directly, it will be set and cleared by
> >>> media_devnode_register and @@ -81,6 +83,8 @@ struct media_file_operations {
> >>> * before registering the node.
> >>> */
> >>> struct media_devnode {
> >>> + struct media_device *media_dev;
> >>> +
> >>> /* device ops */
> >>> const struct media_file_operations *fops;
> >>>
> >>> @@ -103,7 +107,8 @@ struct media_devnode {
> >>> /**
> >>> * media_devnode_register - register a media device node
> >>> *
> >>> - * @devnode: media device node structure we want to register
> >>> + * @media_dev: struct media_device we want to register a device node
> >>> + * @devnode: the device node to unregister
> >>> * @owner: should be filled with %THIS_MODULE
> >>> *
> >>> * The registration code assigns minor numbers and registers the new device
> >>> node @@ -116,7 +121,8 @@ struct media_devnode {
> >>> * the media_devnode structure is *not* called, so the caller is
> >>> responsible for * freeing any data.
> >>> */
> >>> -int __must_check media_devnode_register(struct media_devnode *devnode,
> >>> +int __must_check media_devnode_register(struct media_device *mdev,
> >>> + struct media_devnode *devnode,
> >>> struct module *owner);
> >>>
> >>> /**
> >>> @@ -146,9 +152,14 @@ static inline struct media_devnode
> >>> *media_devnode_data(struct file *filp) * false otherwise.
> >>> *
> >>> * @devnode: pointer to struct &media_devnode.
> >>> + *
> >>> + * Note: If mdev is NULL, it also returns false.
> >>> */
> >>> static inline int media_devnode_is_registered(struct media_devnode
> >>> *devnode) {
> >>> + if (!devnode)
> >>> + return false;
> >>> +
> >>> return test_bit(MEDIA_FLAG_REGISTERED, &devnode->flags);
> >>> }
> >>>
> >>> diff --git a/sound/usb/media.c b/sound/usb/media.c
> >>> index 6db4878045e5..8fed0adec9e1 100644
> >>> --- a/sound/usb/media.c
> >>> +++ b/sound/usb/media.c
> >>> @@ -136,7 +136,7 @@ void media_snd_stream_delete(struct snd_usb_substream
> >>> *subs) struct media_device *mdev;
> >>>
> >>> mdev = mctl->media_dev;
> >>> - if (mdev && media_devnode_is_registered(&mdev->devnode)) {
> >>> + if (mdev && media_devnode_is_registered(mdev->devnode)) {
> >>> media_devnode_remove(mctl->intf_devnode);
> >>> media_device_unregister_entity(&mctl->media_entity);
> >>> media_entity_cleanup(&mctl->media_entity);
> >>> @@ -241,14 +241,14 @@ static void media_snd_mixer_delete(struct
> >>> snd_usb_audio *chip) if (!mixer->media_mixer_ctl)
> >>> continue;
> >>>
> >>> - if (media_devnode_is_registered(&mdev->devnode)) {
> >>> + if (media_devnode_is_registered(mdev->devnode)) {
> >>> media_device_unregister_entity(&mctl->media_entity);
> >>> media_entity_cleanup(&mctl->media_entity);
> >>> }
> >>> kfree(mctl);
> >>> mixer->media_mixer_ctl = NULL;
> >>> }
> >>> - if (media_devnode_is_registered(&mdev->devnode))
> >>> + if (media_devnode_is_registered(mdev->devnode))
> >>> media_devnode_remove(chip->ctl_intf_media_devnode);
> >>> chip->ctl_intf_media_devnode = NULL;
> >>> }
> >>> @@ -268,7 +268,7 @@ int media_snd_device_create(struct snd_usb_audio *chip,
> >>> if (!mdev->dev)
> >>> media_device_usb_init(mdev, usbdev, NULL);
> >>>
> >>> - if (!media_devnode_is_registered(&mdev->devnode)) {
> >>> + if (!media_devnode_is_registered(mdev->devnode)) {
> >>> ret = media_device_register(mdev);
> >>> if (ret) {
> >>> dev_err(&usbdev->dev,
> >>
> >
> >
>
>

--
Thanks,
Mauro