Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[Alexandre Courbot]

On Tue, Jul 4, 2017 at 2:57 PM, Tomasz Figa  wrote:
> Hi Gustavo,
>
> On Tue, Jun 27, 2017 at 12:39 AM, Gustavo Padovan  wrote:
>> 2017-06-18 kbuild test robot :
>>
>>> Hi Gustavo,
>>>
>>> [auto build test ERROR on linuxtv-media/master]
>>> [also build test ERROR on v4.12-rc5 next-20170616]
>>> [if your patch is applied to the wrong git tree, please drop us a note to 
>>> help improve the system]
>>>
>>> url:
>>> https://github.com/0day-ci/linux/commits/Gustavo-Padovan/vb2-add-explicit-fence-user-API/20170618-210740
>>> base:   git://linuxtv.org/media_tree.git master
>>> config: x86_64-allmodconfig (attached as .config)
>>> compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
>>> reproduce:
>>> # save the attached .config to linux build tree
>>> make ARCH=x86_64
>>>
>>> All error/warnings (new ones prefixed by >>):
>>>
>>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
>>> 'atomisp_qbuf':
>>> >> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1297:10: 
>>> >> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you 
>>> >> mean 'reserved'?
>>>  (buf->reserved2 & ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
>>>  ^~
>>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1299:50: 
>>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>>> 'reserved'?
>>>   pipe->frame_request_config_id[buf->index] = buf->reserved2 &
>>>  ^~
>>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
>>> 'atomisp_dqbuf':
>>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1483:5: 
>>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>>> 'reserved'?
>>>  buf->reserved2 = pipe->frame_config_id[buf->index];
>>> ^~
>>>In file included from include/linux/printk.h:329:0,
>>> from include/linux/kernel.h:13,
>>> from include/linux/delay.h:21,
>>> from 
>>> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:24:
>>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1488:6: 
>>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>>> 'reserved'?
>>>   buf->reserved2);
>>>  ^
>>
>> Ouch! Seems the reserved2 was burned down by 2 drivers accessing it
>> without any care for the uAPI. I'll change my patches to use the
>> 'reserved' field instead.
>
> Given that a reserved field has a clear meaning of being reserved and
> the driver in question is in staging. I'd rather vote for fixing the
> driver.

Same here. It seems like this use of reserved2 should not have been
merged in the first place, thankfully it's only in staging.

Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[Tomasz Figa]

Hi Gustavo,

On Tue, Jun 27, 2017 at 12:39 AM, Gustavo Padovan  wrote:
> 2017-06-18 kbuild test robot :
>
>> Hi Gustavo,
>>
>> [auto build test ERROR on linuxtv-media/master]
>> [also build test ERROR on v4.12-rc5 next-20170616]
>> [if your patch is applied to the wrong git tree, please drop us a note to 
>> help improve the system]
>>
>> url:
>> https://github.com/0day-ci/linux/commits/Gustavo-Padovan/vb2-add-explicit-fence-user-API/20170618-210740
>> base:   git://linuxtv.org/media_tree.git master
>> config: x86_64-allmodconfig (attached as .config)
>> compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
>> reproduce:
>> # save the attached .config to linux build tree
>> make ARCH=x86_64
>>
>> All error/warnings (new ones prefixed by >>):
>>
>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
>> 'atomisp_qbuf':
>> >> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1297:10: 
>> >> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>> >> 'reserved'?
>>  (buf->reserved2 & ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
>>  ^~
>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1299:50: 
>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>> 'reserved'?
>>   pipe->frame_request_config_id[buf->index] = buf->reserved2 &
>>  ^~
>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
>> 'atomisp_dqbuf':
>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1483:5: 
>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>> 'reserved'?
>>  buf->reserved2 = pipe->frame_config_id[buf->index];
>> ^~
>>In file included from include/linux/printk.h:329:0,
>> from include/linux/kernel.h:13,
>> from include/linux/delay.h:21,
>> from 
>> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:24:
>>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1488:6: 
>> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>> 'reserved'?
>>   buf->reserved2);
>>  ^
>
> Ouch! Seems the reserved2 was burned down by 2 drivers accessing it
> without any care for the uAPI. I'll change my patches to use the
> 'reserved' field instead.

Given that a reserved field has a clear meaning of being reserved and
the driver in question is in staging. I'd rather vote for fixing the
driver.

Best regards,
Tomasz

Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[Mauro Carvalho Chehab]

Em Fri, 16 Jun 2017 16:39:04 +0900
Gustavo Padovan  escreveu:

> From: Gustavo Padovan 
> 
> Turn the reserved2 field into fence_fd that we will use to send
> an in-fence to the kernel and return an out-fence from the kernel to
> userspace.
> 
> Two new flags were added, V4L2_BUF_FLAG_IN_FENCE, that should be used
> when sending a fence to the kernel to be waited on, and
> V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence.
> 
> Signed-off-by: Gustavo Padovan 
> ---
>  drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 ++--
>  drivers/media/v4l2-core/videobuf2-v4l2.c  | 2 +-
>  include/uapi/linux/videodev2.h| 4 +++-
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c 
> b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> index 6f52970..8f6ab85 100644
> --- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> +++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
> @@ -367,7 +367,7 @@ struct v4l2_buffer32 {
>   __s32   fd;
>   } m;
>   __u32   length;
> - __u32   reserved2;
> + __s32   fence_fd;
>   __u32   reserved;
>  };
>  
> @@ -530,7 +530,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer *kp, 
> struct v4l2_buffer32 __user
>   put_user(kp->timestamp.tv_usec, >timestamp.tv_usec) ||
>   copy_to_user(>timecode, >timecode, sizeof(struct 
> v4l2_timecode)) ||
>   put_user(kp->sequence, >sequence) ||
> - put_user(kp->reserved2, >reserved2) ||
> + put_user(kp->fence_fd, >fence_fd) ||
>   put_user(kp->reserved, >reserved) ||
>   put_user(kp->length, >length))
>   return -EFAULT;
> diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c 
> b/drivers/media/v4l2-core/videobuf2-v4l2.c
> index 0c06699..110fb45 100644
> --- a/drivers/media/v4l2-core/videobuf2-v4l2.c
> +++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
> @@ -203,7 +203,7 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, 
> void *pb)
>   b->timestamp = ns_to_timeval(vb->timestamp);
>   b->timecode = vbuf->timecode;
>   b->sequence = vbuf->sequence;
> - b->reserved2 = 0;
> + b->fence_fd = -1;
>   b->reserved = 0;
>  
>   if (q->is_multiplanar) {
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 2b8feb8..750d511 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -916,7 +916,7 @@ struct v4l2_buffer {
>   __s32   fd;
>   } m;
>   __u32   length;
> - __u32   reserved2;
> + __s32   fence_fd;
>   __u32   reserved;
>  };
>  
> @@ -953,6 +953,8 @@ struct v4l2_buffer {
>  #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE 0x0001
>  /* mem2mem encoder/decoder */
>  #define V4L2_BUF_FLAG_LAST   0x0010

> +#define V4L2_BUF_FLAG_IN_FENCE   0x0020
> +#define V4L2_BUF_FLAG_OUT_FENCE  0x0040

Please document them at Documentation/media/uapi/v4l/buffer.rst.

We'll also need a new chapter at the documentation, describing the
explicit fences mechanism.

>  
>  /**
>   * struct v4l2_exportbuffer - export of video buffer as DMABUF file 
> descriptor


-- 
Thanks,
Mauro

Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[Gustavo Padovan]

2017-06-18 kbuild test robot :

> Hi Gustavo,
> 
> [auto build test ERROR on linuxtv-media/master]
> [also build test ERROR on v4.12-rc5 next-20170616]
> [if your patch is applied to the wrong git tree, please drop us a note to 
> help improve the system]
> 
> url:
> https://github.com/0day-ci/linux/commits/Gustavo-Padovan/vb2-add-explicit-fence-user-API/20170618-210740
> base:   git://linuxtv.org/media_tree.git master
> config: x86_64-allmodconfig (attached as .config)
> compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
> reproduce:
> # save the attached .config to linux build tree
> make ARCH=x86_64 
> 
> All error/warnings (new ones prefixed by >>):
> 
>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
> 'atomisp_qbuf':
> >> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1297:10: 
> >> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
> >> 'reserved'?
>  (buf->reserved2 & ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
>  ^~
>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1299:50: 
> error: 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
> 'reserved'?
>   pipe->frame_request_config_id[buf->index] = buf->reserved2 &
>  ^~
>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
> 'atomisp_dqbuf':
>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1483:5: error: 
> 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
>  buf->reserved2 = pipe->frame_config_id[buf->index];
> ^~
>In file included from include/linux/printk.h:329:0,
> from include/linux/kernel.h:13,
> from include/linux/delay.h:21,
> from 
> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:24:
>drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1488:6: error: 
> 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
>   buf->reserved2);
>  ^

Ouch! Seems the reserved2 was burned down by 2 drivers accessing it
without any care for the uAPI. I'll change my patches to use the
'reserved' field instead.

Gustavo

Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[kbuild test robot]

Hi Gustavo,

[auto build test ERROR on linuxtv-media/master]
[also build test ERROR on v4.12-rc5 next-20170616]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Gustavo-Padovan/vb2-add-explicit-fence-user-API/20170618-210740
base:   git://linuxtv.org/media_tree.git master
config: x86_64-allmodconfig (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64 

All error/warnings (new ones prefixed by >>):

   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
'atomisp_qbuf':
>> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1297:10: error: 
>> 'struct v4l2_buffer' has no member named 'reserved2'; did you mean 
>> 'reserved'?
 (buf->reserved2 & ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
 ^~
   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1299:50: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
  pipe->frame_request_config_id[buf->index] = buf->reserved2 &
 ^~
   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
'atomisp_dqbuf':
   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1483:5: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
 buf->reserved2 = pipe->frame_config_id[buf->index];
^~
   In file included from include/linux/printk.h:329:0,
from include/linux/kernel.h:13,
from include/linux/delay.h:21,
from 
drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:24:
   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1488:6: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
  buf->reserved2);
 ^
   include/linux/dynamic_debug.h:135:9: note: in definition of macro 
'dynamic_dev_dbg'
  ##__VA_ARGS__);  \
^~~
>> drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c:1486:2: note: in 
>> expansion of macro 'dev_dbg'
 dev_dbg(isp->dev, "dqbuf buffer %d (%s) for asd%d with exp_id %d, 
isp_config_id %d\n",
 ^~~
   drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c: At top level:
>> cc1: warning: unrecognized command line option '-Wno-implicit-fallthrough'
--
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
'atomisp_qbuf':
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:1297:10: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
 (buf->reserved2 & ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
 ^~
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:1299:50: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
  pipe->frame_request_config_id[buf->index] = buf->reserved2 &
 ^~
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c: In function 
'atomisp_dqbuf':
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:1483:5: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
 buf->reserved2 = pipe->frame_config_id[buf->index];
^~
   In file included from include/linux/printk.h:329:0,
from include/linux/kernel.h:13,
from include/linux/delay.h:21,
from 
drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:24:
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:1488:6: error: 
'struct v4l2_buffer' has no member named 'reserved2'; did you mean 'reserved'?
  buf->reserved2);
 ^
   include/linux/dynamic_debug.h:135:9: note: in definition of macro 
'dynamic_dev_dbg'
  ##__VA_ARGS__);  \
^~~
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c:1486:2: note: in 
expansion of macro 'dev_dbg'
 dev_dbg(isp->dev, "dqbuf buffer %d (%s) for asd%d with exp_id %d, 
isp_config_id %d\n",
 ^~~
   drivers/staging/media/atomisp/pci/atomisp2/atomisp_ioctl.c: At top level:
>> cc1: warning: unrecognized command line option '-Wno-implicit-fallthrough'

vim +1297 drivers/staging/media//atomisp/pci/atomisp2/atomisp_ioctl.c

a49d2536 Alan Cox 2017-02-17  1291  
a49d2536 Alan Cox 2017-02-17  1292  done:
a49d2536 Alan Cox 2017-02-17  1293  if (!((buf->flags & NOFLUSH_FLAGS) == 
NOFLUSH_FLAGS))
a49d2536 Alan Cox 2017-02-17  1294  wbinvd();
a49d2536 Alan Cox 2017-02-17  1295  
a49d2536 Alan Cox 2017-02-17  1296  if (!atomisp_is_vf_pipe(pipe) &&
a49d2536 Alan Cox 2017-02-17 @1297  (buf->reserved2 & 
ATOMISP_BUFFER_HAS_PER_FRAME_SETTING)) {
a49d2536 Alan Cox 2017-02-17  1298  /* this buffer will have a 

Re: [PATCH 01/12] [media] vb2: add explicit fence user API

[kbuild test robot]

Hi Gustavo,

[auto build test ERROR on linuxtv-media/master]
[also build test ERROR on v4.12-rc5 next-20170616]
[if your patch is applied to the wrong git tree, please drop us a note to help 
improve the system]

url:
https://github.com/0day-ci/linux/commits/Gustavo-Padovan/vb2-add-explicit-fence-user-API/20170618-210740
base:   git://linuxtv.org/media_tree.git master
config: sh-allmodconfig (attached as .config)
compiler: sh4-linux-gnu-gcc (Debian 6.3.0-18) 6.3.0 20170516
reproduce:
wget 
https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=sh 

All errors (new ones prefixed by >>):

   drivers/media//usb/cpia2/cpia2_v4l.c: In function 'cpia2_dqbuf':
>> drivers/media//usb/cpia2/cpia2_v4l.c:951:5: error: 'struct v4l2_buffer' has 
>> no member named 'reserved2'; did you mean 'reserved'?
 buf->reserved2 = 0;
^~

vim +951 drivers/media//usb/cpia2/cpia2_v4l.c

1b18e7a0 drivers/media/usb/cpia2/cpia2_v4l.c   Sakari Ailus 2012-10-22  945 
| V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  946 
buf->field = V4L2_FIELD_NONE;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  947 
buf->timestamp = cam->buffers[buf->index].timestamp;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  948 
buf->sequence = cam->buffers[buf->index].seq;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  949 
buf->m.offset = cam->buffers[buf->index].data - cam->frame_buffer;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  950 
buf->length = cam->frame_size;
2b719d7b drivers/media/video/cpia2/cpia2_v4l.c Sakari Ailus 2012-05-02 @951 
buf->reserved2 = 0;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  952 
buf->reserved = 0;
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  953 
memset(>timecode, 0, sizeof(buf->timecode));
ab33d507 drivers/media/video/cpia2/cpia2_v4l.c Alan Cox 2006-02-27  954  

:: The code at line 951 was first introduced by commit
:: 2b719d7baf490e24ce7d817c6337b7c87fda84c1 [media] v4l: drop 
v4l2_buffer.input and V4L2_BUF_FLAG_INPUT

:: TO: Sakari Ailus 
:: CC: Mauro Carvalho Chehab 

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

[PATCH 01/12] [media] vb2: add explicit fence user API

[Gustavo Padovan]

From: Gustavo Padovan 

Turn the reserved2 field into fence_fd that we will use to send
an in-fence to the kernel and return an out-fence from the kernel to
userspace.

Two new flags were added, V4L2_BUF_FLAG_IN_FENCE, that should be used
when sending a fence to the kernel to be waited on, and
V4L2_BUF_FLAG_OUT_FENCE, to ask the kernel to give back an out-fence.

Signed-off-by: Gustavo Padovan 
---
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 4 ++--
 drivers/media/v4l2-core/videobuf2-v4l2.c  | 2 +-
 include/uapi/linux/videodev2.h| 4 +++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c 
b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index 6f52970..8f6ab85 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -367,7 +367,7 @@ struct v4l2_buffer32 {
__s32   fd;
} m;
__u32   length;
-   __u32   reserved2;
+   __s32   fence_fd;
__u32   reserved;
 };
 
@@ -530,7 +530,7 @@ static int put_v4l2_buffer32(struct v4l2_buffer *kp, struct 
v4l2_buffer32 __user
put_user(kp->timestamp.tv_usec, >timestamp.tv_usec) ||
copy_to_user(>timecode, >timecode, sizeof(struct 
v4l2_timecode)) ||
put_user(kp->sequence, >sequence) ||
-   put_user(kp->reserved2, >reserved2) ||
+   put_user(kp->fence_fd, >fence_fd) ||
put_user(kp->reserved, >reserved) ||
put_user(kp->length, >length))
return -EFAULT;
diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c 
b/drivers/media/v4l2-core/videobuf2-v4l2.c
index 0c06699..110fb45 100644
--- a/drivers/media/v4l2-core/videobuf2-v4l2.c
+++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
@@ -203,7 +203,7 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void 
*pb)
b->timestamp = ns_to_timeval(vb->timestamp);
b->timecode = vbuf->timecode;
b->sequence = vbuf->sequence;
-   b->reserved2 = 0;
+   b->fence_fd = -1;
b->reserved = 0;
 
if (q->is_multiplanar) {
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 2b8feb8..750d511 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -916,7 +916,7 @@ struct v4l2_buffer {
__s32   fd;
} m;
__u32   length;
-   __u32   reserved2;
+   __s32   fence_fd;
__u32   reserved;
 };
 
@@ -953,6 +953,8 @@ struct v4l2_buffer {
 #define V4L2_BUF_FLAG_TSTAMP_SRC_SOE   0x0001
 /* mem2mem encoder/decoder */
 #define V4L2_BUF_FLAG_LAST 0x0010
+#define V4L2_BUF_FLAG_IN_FENCE 0x0020
+#define V4L2_BUF_FLAG_OUT_FENCE0x0040
 
 /**
  * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor
-- 
2.9.4