Some kernel-doc warnings in <media/dvbdev.h> were introduced. A fixup
patch addressed them was already merged, but Randy's approach from:
https://lore.kernel.org/linux-media/20221203060931.19953-1-rdunlap@infradead.org

Had some advantages, as it moves the @dvbdev to the right place inside
dvb_remove_device() documentation and it makes clearer about what
refcounter struct dvb_device refers to.

So, apply the changes suggested by Randy.

Suggested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

dvb_register_device() dynamically allocates fops with kmemdup()
to set the fops->owner.
And these fops are registered in 'file->f_ops' using replace_fops()
in the dvb_device_open() process, and kfree()d in dvb_free_device().

However, it is not common to use dynamically allocated fops instead
of 'static const' fops as an argument of replace_fops(),
and UAF may occur.
These UAFs can occur on any dvb type using dvb_register_device(),
such as dvb_dvr, dvb_demux, dvb_frontend, dvb_net, etc.

So, instead of kfree() the fops dynamically allocated in
dvb_register_device() in dvb_free_device() called during the
.disconnect() process, kfree() it collectively in exit_dvbdev()
called when the dvbdev.c module is removed.

Link: https://lore.kernel.org/linux-media/20221117045925.14297-4-imv4bel@gmail.com
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Previous commit that introduces reference counter does not add proper
comments, which will lead to warning when building htmldocs. Fix them.

Reported-by: "Stephen Rothwell" <sfr@canb.auug.org.au>
Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

dvb_unregister_device() is known that prone to use-after-free.
That is, the cleanup from dvb_unregister_device() releases the dvb_device
even if there are pointers stored in file->private_data still refer to it.

This patch adds a reference counter into struct dvb_device and delays its
deallocation until no pointer refers to the object.

Link: https://lore.kernel.org/linux-media/20220807145952.10368-1-linma@zju.edu.cn
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

Drivers for devices with multiple frontends which cannot be used
concurrently due to hardware limitations which enforce that restriction
by setting the mfe_shared field to 1 exhibit rather unfriendly behavior
towards applications: The unavailable frontend devices cannot be opened
at all, not even for read-only access to query information. Even worse,
any open call is blocked for 5 seconds by default.

Allow drivers for such devices to behave like regular busy frontend
devices instead, i.e. still allowing concurrent read access to the
unavailable frontend and denying concurrent write access with -EBUSY
without delay.

This patch does not alter the behavior of any existing driver to avoid
regressions. Driver developers who wish to take advantage of this must
ensure their driver can handle all read-only accesses to the unavailable
frontend, and indicate the capability by setting the mfe_shared field to
2 instead of 1.

Add a check to dvb-usb-init.c when automatically setting the mfe_shared
field that when a driver has already set the field to 2, it is not
overwritten.

Document the additional capability in the code comment about mfe_shared.

Link: https://lore.kernel.org/linux-media/trinity-22c77578-26b0-4867-9ff7-2668e5d22c64-1642799929896@3c-app-gmx-bap04
Signed-off-by: Robert Schlabbach <robert_s@gmx.net>
Tested-by: Robert Schlabbach <robert_s@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

The syntax without dots is available since commit 43756e347f21
("scripts/kernel-doc: Add support for named variable macro arguments").

The same HTML output is produced with and without this patch.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Some identifiers have different names between their prototypes
and the kernel-doc markup. Seome seems to be due to cut-and-paste
related issues.

Others need to be fixed, as kernel-doc markups should use this format:
        identifier - description

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com> # IPU3 and V4L2
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Having the '*' in the next line separated from the type makes it
hard to see that these functions return a pointer to that type.

Instead, keep it next to the type name so it is clear that it is
a pointer to that type.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Change the doubled word "the" in a comment to "to the".

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Fix minor typos in the DVB demux documentation.

Signed-off-by: Marc Gonzalez <marc.w.gonzalez@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>