If __reqbufs was called then existing buffers are freed. However, if that
happens without ever having started STREAMON, but if buffers have been queued,
then the buf_finish op is never called.

Add a call to __vb2_queue_cancel in __reqbufs so that these buffers are
cleaned up there as well.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

In commit 02f142ec support was added to
start_streaming to return -ENOBUFS if insufficient buffers were queued
for the DMA engine to start. The vb2 core would attempt calling
start_streaming again if another buffer would be queued up.

Later analysis uncovered problems with the queue management if start_streaming
would return an error: the buffers are enqueued to the driver before the
start_streaming op is called, so after an error they are never returned to
the vb2 core. The solution for this is to let the driver return them to
the vb2 core in case of an error while starting the DMA engine. However,
in the case of -ENOBUFS that would be weird: it is not a real error, it
just says that more buffers are needed. Requiring start_streaming to give
them back only to have them requeued again the next time the application
calls QBUF is inefficient.

This patch changes this mechanism: it adds a 'min_buffers_needed' field
to vb2_queue that drivers can set with the minimum number of buffers
required to start the DMA engine. The start_streaming op is only called
if enough buffers are queued. The -ENOBUFS handling has been dropped in
favor of this new method.

Drivers are expected to return buffers back to vb2 core with state QUEUED
if start_streaming would return an error. The vb2 core checks for this
and produces a warning if that didn't happen and it will forcefully
reclaim such buffers to ensure that the internal vb2 core state remains
consistent and all buffer-related resources have been correctly freed
and all op calls have been balanced.

__reqbufs() has been updated to check that at least min_buffers_needed
buffers could be allocated. If fewer buffers were allocated then __reqbufs
will free what was allocated and return -ENOMEM. Based on a suggestion from
Pawel Osciak.

__create_bufs() doesn't do that check, since the use of __create_bufs
assumes some advance scenario where the user might want more control.
Instead streamon will check if enough buffers were allocated to prevent
streaming with fewer than the minimum required number of buffers.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

__vb2_queue_free() would init the queued_list at all times, even if
q->num_buffers > 0. This should only happen if num_buffers == 0.

This situation can happen if a CREATE_BUFFERS call couldn't allocate
enough buffers and had to free those it did manage to allocate before
returning an error.

While we're at it: __vb2_queue_alloc() returns the number of buffers
allocated, not an error code. So stick the result in allocated_buffers
instead of ret as that's very confusing.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

'queued_count' is a bit vague since it is not clear to which queue it
refers to: the vb2 internal list of buffers or the driver-owned list
of buffers.

Rename to make it explicit.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NPawel Osciak <pawel@osciak.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Ensure that these ops are properly balanced.

There are two scenarios:

1) for MMAP buf_init is called when the buffers are created and buf_cleanup
   must be called when the queue is finally freed. This scenario was always
   working.

2) for USERPTR and DMABUF it is more complicated. When a buffer is queued
   the code checks if all planes of this buffer have been acquired before.
   If that's the case, then only buf_prepare has to be called. Otherwise
   buf_cleanup needs to be called if the buffer was acquired before, then,
   once all changed planes have been (re)acquired, buf_init has to be
   called followed by buf_prepare. Should buf_prepare fail, then buf_cleanup
   must be called on the newly acquired planes to release them in.

Finally, in __vb2_queue_free we have to check if the buffer was actually
acquired before calling buf_cleanup. While that it always true for MMAP
mode, it is not necessarily true for the other modes. E.g. if you just
call REQBUFS and close the file handle, then buffers were never queued and
so no buf_init was ever called.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

If a queue was canceled, then the buf_finish op was never called for the
pending buffers. So add this call to queue_cancel. Before calling buf_finish
set the buffer state to PREPARED, which is the correct state. That way the
states DONE and ERROR will only be seen in buf_finish if streaming is in
progress.

Since buf_finish can now be called from non-streaming state we need to
adapt the handful of drivers that actually need to know this.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The buf_finish op should always work, so change the return type to void.
Update the few drivers that use it.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NPawel Osciak <pawel@osciak.com>
Reviewed-by: NPawel Osciak <pawel@osciak.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

When a vb2_queue is freed check if all the mem_ops and queue ops were balanced.
So the number of calls to e.g. buf_finish has to match the number of calls to
buf_prepare, etc.

This code is only enabled if CONFIG_VIDEO_ADV_DEBUG is set.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NPawel Osciak <pawel@osciak.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Fix an incorrect test in vb2_internal_qbuf() where only DEQUEUED buffers
are allowed. But PREPARED buffers are also OK.

Introduced by commit 4138111a
("vb2: simplify qbuf/prepare_buf by removing callback").
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Commit 88e26870 ("vb2: Improve file I/O
emulation to handle buffers in any order") broke read/write support if
the size of the buffer being read/written is less than the size of the
image.

When the commit was tested originally I used qv4l2, which calls read()
with exactly the size of the image. But if you try 'cat /dev/video0'
then it will fail and typically hang after reading two buffers.

This patch fixes the behavior by adding a new cur_index field that
contains the index of the field currently being filled/read, or it
is num_buffers in which case a new buffer needs to be dequeued.

The old index field has been renamed to initial_index in order to be
a bit more descriptive.

This has been tested with both read and write.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Tested-by: NHans Verkuil <hans.verkuil@cisco.com>
Cc: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

This patch adds a test preventing streamon() if there is no buffer
ready.

Without this patch, a user could call streamon() before
preparing any buffer. This leads to a situation where if he calls
close() before calling streamoff() the device is kept streaming.
Signed-off-by: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

For COPY timestamps, buffer timestamp source flags will traverse the queue
untouched.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Some devices do not produce timestamps that correspond to the end of the
frame. The user space should be informed on the matter. This patch achieves
that by adding buffer flags (and a mask) for timestamp sources since more
possible timestamping points are expected than just two.

A three-bit mask is defined (V4L2_BUF_FLAG_TSTAMP_SRC_MASK) and two of the
eight possible values is are defined V4L2_BUF_FLAG_TSTAMP_SRC_EOF for end of
frame (value zero) V4L2_BUF_FLAG_TSTAMP_SRC_SOE for start of exposure (next
value).
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NKamil Debski <k.debski@samsung.com>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Mask out other bits when comparing timestamp types.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The timestamp_type field used to contain only the timestamp type. Soon it
will be used for timestamp source flags as well. Rename the field
accordingly.

[m.chehab@samsung.com: do the change also to drivers/staging/media and at s2255]
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

When sending a buffer to a video output device some of the fields need
to be copied so they arrive in the driver. These are the KEY/P/BFRAME
flags and the TIMECODE flag, and, if that flag is set, the timecode field
itself.

There are a number of functions involved in this: the __fill_vb2_buffer()
is called while preparing a buffer. For output buffers the buffer contains
the video data, so any meta data associated with that (KEY/P/BFRAME and
the field information) should be stored at that point.

The timecode, timecode flag and timestamp information is not part of that,
that information will have to be set when vb2_internal_qbuf() is called to
actually queue the buffer to the driver. Usually VIDIOC_QBUF will do the
prepare as well, but you can call PREPARE_BUF first and only later VIDIOC_QBUF.
You most likely will want to set the timestamp and timecode when you actually
queue the buffer, not when you prepare it.

Finally, in buf_prepare() make sure the timestamp and sequence fields are
actually cleared so that when you do a QUERYBUF of a prepared-but-not-yet-queued
buffer you will not see stale timestamp/sequence data.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Modern silicon RF tuners used nowadays has many controllable gain
stages on signal path. Usually, but not always, there is at least
3 gain stages. Also on some cases there could be multiple gain
stages within the ones specified here. However, I think that having
these three controllable gain stages offers enough fine-tuning for
real use cases.

1) LNA gain. That is first gain just after antenna input.
2) Mixer gain. It is located quite middle of the signal path, where
RF signal is down-converted to IF/BB.
3) IF gain. That is last gain in order to adjust output signal level
to optimal level for receiving party (usually demodulator ADC).

Each gain stage could be set rather often both manual or automatic
(AGC) mode. Due to that add separate controls for controlling
operation mode.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Modulator ioctls could be enabled mistakenly for non-radio devices.
Currently those ioctls are only valid for radio. Fix it.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Enable stream format (FMT) IOCTLs for SDR use. These are used for negotiate
used data stream format.

Reorganise some some IOCTL selection logic.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Acked-by: NHans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Add new V4L2 stream format definition, V4L2_BUF_TYPE_SDR_CAPTURE,
for SDR receiver.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Define tuner types V4L2_TUNER_ADC and V4L2_TUNER_RF for SDR usage.

ADC is used for setting sampling rate (sampling frequency) to SDR
device.

Another tuner type, named as V4L2_TUNER_RF, is possible RF tuner.
Is is used to down-convert RF frequency to range ADC could sample.
Having RF tuner is optional, whilst in practice it is almost always
there.

Also add checks to VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY and
VIDIOC_ENUM_FREQ_BANDS only allow these two tuner types when device
type is SDR (VFL_TYPE_SDR). For VIDIOC_G_FREQUENCY we do not check
tuner type, instead override type with V4L2_TUNER_ADC in every
case (requested by Hans in order to keep functionality in line with
existing tuners and existing API does not specify it).

Prohibit VIDIOC_S_HW_FREQ_SEEK explicitly when device type is SDR,
as device cannot do hardware seek without a hardware demodulator.
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Add new V4L device type VFL_TYPE_SDR for Software Defined Radio.
It is registered as /dev/swradio0 (/dev/sdr0 was already reserved).
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Adding V4L2 controls for horizontal and vertical search range in pixels
for motion estimation module in video encoder.
Signed-off-by: NSwami Nathan <swaminath.p@samsung.com>
Signed-off-by: NAmit Grover <amit.grover@samsung.com>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: NKamil Debski <k.debski@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Add support for 32-bit ioctls with v4l-subdev device nodes.

Rather than keep adding new ioctls to the list in v4l2-compat-ioctl32.c, just check
if the ioctl is a non-private V4L2 ioctl and if so, call the conversion code.

We keep forgetting to add new ioctls, so this is a more robust solution.

In addition extend the subdev API with support for a compat32 function to
convert custom v4l-subdev ioctls.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Tested-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The VESA standard added a version 2 of the reduced blanking formula.
Note in the comment that this is not yet supported by the v4l2_detect_cvt
function. Obviously this should be implemented eventually, but for now add
this as a reminder.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Round off image width to nearest 8 (GTF_CELL_GRAN)

A source sending a GTF (Generalized Timing Formula) format have no means of
signalling image width. The assumed aspect ratio may result in an odd image
width but according to the standard image width should be in multiple of 8.

Cc: Mats Randgaard <matrandg@cisco.com>
Signed-off-by: NMartin Bugge <marbugge@cisco.com>
Reviewed-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

This patch adds a test preventing streamon() if there is no buffer
ready.

Without this patch, a user could call streamon() before
preparing any buffer. This leads to a situation where if he calls
close() before calling streamoff() the device is kept streaming.
Signed-off-by: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Reviewed-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

This reverts commit a242f426.

That commit actually caused deadlocks, rather then fixing them.

If ext_lock is set to NULL (otherwise videobuf_queue_lock doesn't do
anything), then you get this deadlock:

The driver's mmap function calls videobuf_mmap_mapper which calls
videobuf_queue_lock on q. videobuf_mmap_mapper calls  __videobuf_mmap_mapper,
__videobuf_mmap_mapper calls videobuf_vm_open and videobuf_vm_open
calls videobuf_queue_lock on q (introduced by above patch): deadlocked.

This affects drivers using dma-contig and dma-vmalloc. Only dma-sg is
not affected since it doesn't call videobuf_vm_open from __videobuf_mmap_mapper.

Most drivers these days have a non-NULL ext_lock. Those that still use
NULL there are all fairly obscure drivers, which is why this hasn't been
seen earlier.

Since everything worked perfectly fine for many years I prefer to just
revert this patch rather than trying to fix it. videobuf is quite fragile
and I rather not touch it too much. Work is (slowly) progressing to move
everything over to vb2 or at the very least use non-NULL ext_lock in
videobuf.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org>      # for v3.11 and up
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Reported-by: NPete Eberlein <pete@sensoray.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The side effect of commit 1056e438 ("v4l2-dev: Fix race condition on
__video_register_device") is the increased number of index value assigned
on video_device registration. Before that commit video_devices were
numbered from 0, after it, the indexes starts from 1, because get_index()
always count the device, which is being registered. Some device drivers
rely on video_device index number for internal purposes, i.e. s5p-mfc
driver stopped working after that patch. This patch restores the old method
of numbering the video_device indexes.

Cc: stable@vger.kernel.org # for v3.12
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: NRicardo Ribalda <ricardo.ribalda@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Add v4l2 controls to set desired profile for VP8 encoder.
Acceptable levels for VP8 encoder are
0: Version 0
1: Version 1
2: Version 2
3: Version 3
Signed-off-by: NKiran AVND <avnd.kiran@samsung.com>
Signed-off-by: NPawel Osciak <posciak@chromium.org>
Signed-off-by: NArun Kumar K <arun.kk@samsung.com>
Signed-off-by: NKamil Debski <k.debski@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Adds v4l2 controls to set MIN, MAX QP values and
I, P frame QP for vp8 encoder.
Signed-off-by: NKiran AVND <avnd.kiran@samsung.com>
Signed-off-by: NArun Kumar K <arun.kk@samsung.com>
Signed-off-by: NKamil Debski <k.debski@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The comment incorrectly explains that the code verifies information
provided by userspace, while verification has been performed earlier in
reality. Fix it.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

videobuf2 file I/O emulation assumed that buffers dequeued from the
driver would return in the order they were enqueued in the driver.

Improve the file I/O emulator's book-keeping to remove this assumption.

Also set the buf->size properly if a write() dequeues a buffer and the
VB2_FILEIO_WRITE_IMMEDIATELY flag is set.

Based on an initial patch by Andy Walls.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: NAndy Walls <awalls@md.metrocast.net>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Two fixes:

- there is no need to set the index when calling dqbuf: dqbuf will
  overwrite it.
- __vb2_init_fileio already starts streaming for write(), so there is
  no need to do it again in __vb2_perform_fileio. It can never have
  worked anyway: either __vb2_init_fileio succeeds in starting streaming
  or it is never going to happen.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

If start_streaming returns -ENOBUFS, then it will be retried the next time
a buffer is queued. This means applications no longer need to know how many
buffers need to be queued before STREAMON can be called. This is particularly
useful for output stream I/O.

If a DMA engine needs at least X buffers before it can start streaming, then
for applications to get a buffer out as soon as possible they need to know
the minimum number of buffers to queue before STREAMON can be called. You can't
just try STREAMON after every buffer since on failure STREAMON will dequeue
all your buffers. (Is that a bug or a feature? Frankly, I'm not sure).

This patch simplifies applications substantially: they can just call STREAMON
at the beginning and then start queuing buffers and the DMA engine will
kick in automagically once enough buffers are available.

This also fixes using write() to stream video: the fileio implementation
calls streamon without having any queued buffers, which will fail today for
any driver that requires a minimum number of buffers.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The read/write implementation in vb2 reuses existing vb2 functions, but
it sets q->fileio to NULL before calling them in order to skip the
'q->fileio != NULL' check.

This works today due to the synchronous nature of read/write, but it
1) is ugly, and 2) will fail in an asynchronous use-case such as a
thread queuing and dequeuing buffers. This last example will be necessary
in order to implement vb2 DVB support.

This patch removes the hack by splitting up the dqbuf/qbuf/streamon/streamoff
functions into an external and an internal version. The external version
checks q->fileio and then calls the internal version. The read/write
implementation now just uses the internal version, removing the need to
set q->fileio to NULL.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

When preparing a buffer the queue lock is released for a short while
if the memory mode is USERPTR (see __buf_prepare for the details), which
would allow a race with a REQBUFS which can free the buffers. Removing the
buffers from underneath __buf_prepare is obviously a bad idea, so we
check if any of the buffers is in the state PREPARING, and if so we
just return -EAGAIN.

If this happens, then the application does something really strange. The
REQBUFS call can be retried safely, since this situation is transient.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The callback used to merge the common code of the qbuf/prepare_buf
code can be removed now that the mmap_sem handling is pushed down to
__buf_prepare(). This makes the code more readable.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Changeset b18a8ff2 added a comment violating the 80cols max size,
with no good reason.

Fix it.

Cc: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Rather than taking the mmap semaphore at a relatively high-level function,
push it down to the place where it is really needed.

It was placed in vb2_queue_or_prepare_buf() to prevent racing with other
vb2 calls. The only way I can see that a race can happen is when two
threads queue the same buffer. The solution for that it to introduce
a PREPARING state.

Moving it down offers opportunities to simplify the code.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>