linux.git/include/media/v4l2-dev.h, branch v3.6

[media] v4l2-dev/ioctl.c: add vb2_queue support to video_device

2012-07-06T20:30:54+00:00

This prepares struct video_device for easier integration with vb2.

It also introduces a new lock that protects the vb2_queue. It is up
to the driver to use it or not. And the driver can associate an owner
filehandle with the queue to check whether queuing requests are
permitted for the calling filehandle.

Signed-off-by: Hans Verkuil 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2-dev: rename two functions

2012-05-14T18:06:50+00:00

Rename the function v4l2_dont_use_lock to v4l2_disable_ioctl_locking,
and rename v4l2_dont_use_cmd to v4l2_disable_ioctl.

Signed-off-by: Hans Verkuil 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2-dev.h: add comment not to use V4L2_FL_LOCK_ALL_FOPS in new drivers

2012-05-14T18:06:25+00:00

This flag is for legacy drivers only and will go away in the future.

A note regarding commit 5126f2590bee412e3053de851cb07f531e4be36a
(v4l2-dev: add flag to have the core lock all file operations):

That commit message suggests that by not taking the core lock for fops
other than unlocked_ioctl all problems relating to AB-BA locking and
mm->mmap_sem are solved. This is not the case.

More work needs to be done by moving the core lock further down into
video_ioctl2. It should only be taken after the copy_from/to_user calls
are done.

Signed-off-by: Hans Verkuil 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2-dev: add flag to have the core lock all file operations

2012-05-14T12:19:38+00:00

This used to be the default if the lock pointer was set, but now that lock is by
default only used for ioctl serialization. Those drivers that already used
core locking have this flag set explicitly, except for some drivers where
it was obvious that there was no need to serialize any file operations other
than ioctl.

The drivers that didn't need this flag were:

drivers/media/radio/dsbr100.c
drivers/media/radio/radio-isa.c
drivers/media/radio/radio-keene.c
drivers/media/radio/radio-miropcm20.c
drivers/media/radio/radio-mr800.c
drivers/media/radio/radio-tea5764.c
drivers/media/radio/radio-timb.c
drivers/media/video/vivi.c
sound/i2c/other/tea575x-tuner.c

The other drivers that use core locking and where it was not immediately
obvious that this flag wasn't needed were changed so that the flag is set
together with a comment that that driver needs work to avoid having to
set that flag. This will often involve taking the core lock in the fops
themselves.

Eventually this flag should go and it should not be used in new drivers.

There are a few reasons why we want to avoid core locking of non-ioctl
fops: in the case of mmap this can lead to a deadlock in rare situations
since when mmap is called the mmap_sem is held and it is possible for
other parts of the code to take that lock as well (copy_from_user()/copy_to_user()
perform a down_read(&mm->mmap_sem) when a page fault occurs).

It is very unlikely that that happens since the core lock serializes all
fops, but the kernel warns about it if lock validation is turned on.

For poll it is also undesirable to take the core lock as that can introduce
increased latency. The same is true for read/write.

While it was possible to make flags or something to turn on/off taking the
core lock for each file operation, in practice it is much simpler to just
not take it at all except for ioctl and leave it to the driver to take the
lock. There are only a handful fops compared to the zillion ioctls we have.

I also wanted to make it obvious which drivers still take the lock for all
fops, so that's why I chose to have drivers set it explicitly.

Signed-off-by: Hans Verkuil 
Acked-by: Hans de Goede 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2-dev/ioctl: determine the valid ioctls upfront

2012-05-14T12:17:28+00:00

Rather than testing whether an ioctl is implemented in the driver or not
every time the ioctl is called, do it upfront when the device is registered.

This also allows a driver to disable certain ioctls based on the capabilities
of the detected board, something you can't do today without creating separate
v4l2_ioctl_ops structs for each new variation.

For the most part it is pretty straightforward, but for control ioctls a flag
is needed since it is possible that you have per-filehandle controls, and that
can't be determined upfront of course.

Signed-off-by: Hans Verkuil 
Acked-by: Hans de Goede 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2-dev: make it possible to skip locking for selected ioctls

2012-05-14T12:13:43+00:00

Using the V4L2 core lock is a very robust method that is usually very good
at doing the right thing. But some drivers, particularly USB drivers, may
want to prevent the core from taking the lock for specific ioctls, particularly
buffer queuing ioctls.

The reason is that certain commands like S_CTRL can take a long time to process
over USB and all the time the core has the lock, preventing VIDIOC_DQBUF from
proceeding, even though a frame may be ready in the queue.

This introduces unwanted latency.

Since the buffer queuing commands often have their own internal lock it is
often not necessary to take the core lock. Drivers can now say that they don't
want the core to take the lock for specific ioctls.

As it is a specific opt-out it makes it clear to the reviewer that those
ioctls will need more care when reviewing.

Signed-off-by: Hans Verkuil 
Acked-by: Hans de Goede 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l: Add custom compat_ioctl32 operation

2012-03-19T17:06:12+00:00

Drivers implementing custom ioctls need to handle 32-bit/64-bit
compatibility themselves. Provide them with a way to do so.

To avoid circular module dependencies, merge the v4l2-compat-ioctl32
module into videodev. There is no point in keeping them separate, as the
v4l2_compat_ioctl32() function is required by videodev if CONFIG_COMPAT
is set anyway.

Signed-off-by: Laurent Pinchart 
Reviewed-by: Hans Verkuil 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l: Fix media_entity_to_video_device macro argument name

2011-06-01T12:42:03+00:00

The name 'entity' is used twice in the macro body, once as the macro
argument, and once as a structure field name. This breaks compilation if
the macro is called with its argument not named 'entity'.

Fix this by renaming the macro argument '__e'. This should avoid
namespace clashes.

Signed-off-by: Laurent Pinchart 
Signed-off-by: Mauro Carvalho Chehab

[media] Revert "V4L/DVB: v4l2-dev: remove get_unmapped_area"

2011-05-20T15:14:40+00:00

This reverts commit c29fcff3daafbf46d64a543c1950bbd206ad8c1c.

Signed-off-by: Bob Liu 
Signed-off-by: Mauro Carvalho Chehab

[media] v4l2: use new flag to enable core priority handling

2011-03-22T19:38:16+00:00

Rather than guess which driver supports core priority handling, require drivers
that do to explicitly set the V4L2_FL_USE_FH_PRIO flag in video_device.

Updated the core prio handling accordingly and set the flag in the three
drivers that do.

Signed-off-by: Hans Verkuil 
Signed-off-by: Mauro Carvalho Chehab