This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:

    for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
        L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
        for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
    done

with de-mangling cleanups yet to come.

NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do.  But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.

The next patch from Al will sort out the final differences, and we
should be all done.
Scripted-by: NAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

There are multiple places where arrays or otherwise variable sized
buffer are allocated through V4L2 core code, including things like
controls, memory pages, staging buffers for ioctls and so on. Such
allocations can potentially require an order > 0 allocation from the
page allocator, which is not guaranteed to be fulfilled and is likely to
fail on a system with severe memory fragmentation (e.g. a system with
very long uptime).

Since the memory being allocated is intended to be used by the CPU
exclusively, we can consider using vmalloc() as a fallback and this is
exactly what the recently merged kvmalloc() helpers do. A kmalloc() call
is still attempted, even for order > 0 allocations, but it is done
with __GFP_NORETRY and __GFP_NOWARN, with expectation of failing if
requested memory is not available instantly. Only then the vmalloc()
fallback is used. This should give us fast and more reliable allocations
even on systems with higher memory pressure and/or more fragmentation,
while still retaining the same performance level on systems not
suffering from such conditions.

While at it, replace explicit array size calculations on changed
allocations with kvmalloc_array().

Purposedly not touching videobuf1, as it is deprecated, has only few
users remaining and would rather be seen removed instead.
Signed-off-by: NTomasz Figa <tfiga@chromium.org>
Acked-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Drop the FSF's postal address from the source code files that typically
contain mostly the license text. Of the 628 removed instances, 578 are
outdated.

The patch has been created with the following command without manual edits:

git grep -l "675 Mass Ave\|59 Temple Place\|51 Franklin St" -- \
	drivers/media/ include/media|while read i; do i=$i perl -e '
open(F,"< $ENV{i}");
$a=join("", <F>);
$a =~ s/[ \t]*\*\n.*You should.*\n.*along with.*\n.*(\n.*USA.*$)?\n//m
	&& $a =~ s/(^.*)Or, (point your browser to) /$1To obtain the license, $2\n$1/m;
close(F);
open(F, "> $ENV{i}");
print F $a;
close(F);'; done
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>

This header were poorly documented, and weren't using the
kernel-doc format. Document everything but the macros using
the right format.

While here, also fix the other comments to match the
Linux CodingStyle.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

According to the V4L2 API, the VIDIOC_STREAMON ioctl should return EPIPE
if there is a format mismatch in the pipeline configuration.

As the .vidioc_streamon in the v4l2_ioctl_ops usually forwards the error
caused by the v4l2_subdev_link_validate_default (if it is in use), it
should return -EPIPE when it detect the mismatch.

When an entity is connected to a non enabled link,
media_entity_pipeline_start should return -ENOLINK, as the link does not
exist.
Signed-off-by: NHelen Mae Koike Fornazier <helen.koike@collabora.co.uk>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Add a new subdev operation to initialize a subdev pad config array, and
a helper function to allocate and initialize the array. This can be used
by bridge drivers to implement try format based on subdev pad
operations.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@linaro.org>
Acked-by: NVaibhav Hiremath <vaibhav.hiremath@linaro.org>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Code that processes media entities can require knowledge of the
structure type that embeds a particular media entity instance in order
to cast the entity to the proper object type. This needs is shown by the
presence of the is_media_entity_v4l2_io and is_media_entity_v4l2_subdev
functions.

The implementation of those two functions relies on the entity function
field, which is both a wrong and an inefficient design, without even
mentioning the maintenance issue involved in updating the functions
every time a new entity function is added. Fix this by adding add an
obj_type field to the media entity structure to carry the information.
Signed-off-by: NLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Rename the userspace types from MEDIA_ENT_T_ to MEDIA_ENT_F_
and add the backward compatibility bits.

The changes at the .c files was generated by the following
coccinelle script:

@@
@@
-MEDIA_ENT_T_UNKNOWN
+MEDIA_ENT_F_UNKNOWN
@@
@@
-MEDIA_ENT_T_DVB_BASE
+MEDIA_ENT_F_DVB_BASE
@@
@@
-MEDIA_ENT_T_V4L2_BASE
+MEDIA_ENT_F_V4L2_BASE
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_BASE
+MEDIA_ENT_F_V4L2_SUBDEV_BASE
@@
@@
-MEDIA_ENT_T_CONNECTOR_BASE
+MEDIA_ENT_F_CONNECTOR_BASE
@@
@@
-MEDIA_ENT_T_V4L2_VIDEO
+MEDIA_ENT_F_IO_V4L
@@
@@
-MEDIA_ENT_T_V4L2_VBI
+MEDIA_ENT_F_IO_VBI
@@
@@
-MEDIA_ENT_T_V4L2_SWRADIO
+MEDIA_ENT_F_IO_SWRADIO
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_UNKNOWN
+MEDIA_ENT_F_V4L2_SUBDEV_UNKNOWN
@@
@@
-MEDIA_ENT_T_CONN_RF
+MEDIA_ENT_F_CONN_RF
@@
@@
-MEDIA_ENT_T_CONN_SVIDEO
+MEDIA_ENT_F_CONN_SVIDEO
@@
@@
-MEDIA_ENT_T_CONN_COMPOSITE
+MEDIA_ENT_F_CONN_COMPOSITE
@@
@@
-MEDIA_ENT_T_CONN_TEST
+MEDIA_ENT_F_CONN_TEST
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_SENSOR
+MEDIA_ENT_F_CAM_SENSOR
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_FLASH
+MEDIA_ENT_F_FLASH
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_LENS
+MEDIA_ENT_F_LENS
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_DECODER
+MEDIA_ENT_F_ATV_DECODER
@@
@@
-MEDIA_ENT_T_V4L2_SUBDEV_TUNER
+MEDIA_ENT_F_TUNER
@@
@@
-MEDIA_ENT_T_DVB_DEMOD
+MEDIA_ENT_F_DTV_DEMOD
@@
@@
-MEDIA_ENT_T_DVB_DEMUX
+MEDIA_ENT_F_TS_DEMUX
@@
@@
-MEDIA_ENT_T_DVB_TSOUT
+MEDIA_ENT_F_IO_DTV
@@
@@
-MEDIA_ENT_T_DVB_CA
+MEDIA_ENT_F_DTV_CA
@@
@@
-MEDIA_ENT_T_DVB_NET_DECAP
+MEDIA_ENT_F_DTV_NET_DECAP
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Entities should have one or more functions. Calling it as a
type proofed to not be correct, as an entity could eventually
have more than one type.

So, rename the field as function.

Please notice that this patch doesn't extend support for
multiple function entities. Such change will happen when
we have real case drivers using it.

No functional changes.
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Instead of abusing MEDIA_ENT_T_V4L2_SUBDEV, initialize
new subdev entities as MEDIA_ENT_T_UNKNOWN.
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Instead of relying on media subtype, use the new macros to detect
if an entity is a subdev or an A/V DMA entity.

Please note that most drivers assume that there's just AV_DMA or
V4L2 subdevs. This is not true anymore, as we've added MC support
for DVB, and there are plans to add support for ALSA and FB/DRM
too.

Ok, on the current pipelines supported by those drivers, just V4L
stuff are there, but, assuming that some day a pipeline that also
works with other subsystems will ever added, it is better to add
explicit checks for the AV_DMA stuff.
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Now that interfaces and entities are distinct, it makes no sense
of keeping something named as MEDIA_ENT_T_DEVNODE.

This change was done with this script:

	for i in $(git grep -l MEDIA_ENT_T|grep -v uapi/linux/media.h); do sed s,MEDIA_ENT_T_DEVNODE_V4L,MEDIA_ENT_T_V4L2_VIDEO, <$i >a && mv a $i; done
Acked-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Add a new helper function called v4l2_subdev_notify_event() which will
deliver the specified event to both the v4l2 subdev event queue as well as
to the notify callback. The former is typically used by userspace
applications to listen to notification events while the later is used by
bridge drivers. Combining both into the same function avoids boilerplate
code in subdev drivers.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

The media_entity_put() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Return an error if an invalid 'which' valid is passed in.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Tested-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

If a subdevice pad op is called from a bridge driver, then there is
no v4l2_subdev_fh struct that can be passed to the subdevice. This
made it hard to use such subdevs from a bridge driver.

This patch replaces the v4l2_subdev_fh pointer by a v4l2_subdev_pad_config
pointer in the pad ops. This allows bridge drivers to use the various
try_ pad ops by creating a v4l2_subdev_pad_config struct and passing it
along to the pad op.

The v4l2_subdev_get_try_* macros had to be changed because of this, so
I also took the opportunity to use the full name of the v4l2_subdev_get_try_*
functions in the __V4L2_SUBDEV_MK_GET_TRY macro arguments: if you now do
'git grep v4l2_subdev_get_try_format' you will actually find the header
where it is defined.

One remark regarding the drivers/staging/media/davinci_vpfe patches: the
*_init_formats() functions assumed that fh could be NULL. However, that's
not true for this driver, it's always set. This is almost certainly a copy
and paste from the omap3isp driver. I've updated the code to reflect the
fact that fh is never NULL.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Tested-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

Drop the duplicate get/set_crop pad ops and only use get/set_selection.
It makes no sense to have two duplicate ops in the internal subdev API.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

The field order must match between the source and sink pads, or the sink
pad field order must be NONE. This allows connecting an interlaced
source to a bridge that has no hardware support for interlaced formats.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: NEnrico Butera <ebutera@users.sourceforge.net>
Acked-by: NSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

As reported by Kbuildtest:

   drivers/media/v4l2-core/v4l2-subdev.c: In function 'check_format':
   drivers/media/v4l2-core/v4l2-subdev.c:136:23: error: 'struct v4l2_subdev' has no member named 'entity'
     if (format->pad >= sd->entity.num_pads)
                          ^
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'check_crop':
   drivers/media/v4l2-core/v4l2-subdev.c:148:21: error: 'struct v4l2_subdev' has no member named 'entity'
     if (crop->pad >= sd->entity.num_pads)
                        ^
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'check_selection':
   drivers/media/v4l2-core/v4l2-subdev.c:161:20: error: 'struct v4l2_subdev' has no member named 'entity'
     if (sel->pad >= sd->entity.num_pads)
                       ^
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'check_edid':
   drivers/media/v4l2-core/v4l2-subdev.c:169:21: error: 'struct v4l2_subdev' has no member named 'entity'
     if (edid->pad >= sd->entity.num_pads)
                        ^
   drivers/media/v4l2-core/v4l2-subdev.c: In function 'subdev_do_ioctl':
>> drivers/media/v4l2-core/v4l2-subdev.c:186:6: warning: unused variable 'rval' [-Wunused-variable]
     int rval;
         ^
   drivers/media/v4l2-core/v4l2-subdev.c: At top level:
   drivers/media/v4l2-core/v4l2-subdev.c:129:12: warning: 'check_format' defined but not used [-Wunused-function]
    static int check_format(struct v4l2_subdev *sd,
               ^
   drivers/media/v4l2-core/v4l2-subdev.c:142:12: warning: 'check_crop' defined but not used [-Wunused-function]
    static int check_crop(struct v4l2_subdev *sd, struct v4l2_subdev_crop *crop)
               ^
   drivers/media/v4l2-core/v4l2-subdev.c:154:12: warning: 'check_selection' defined but not used [-Wunused-function]
    static int check_selection(struct v4l2_subdev *sd,
               ^
   drivers/media/v4l2-core/v4l2-subdev.c:167:12: warning: 'check_edid' defined but not used [-Wunused-function]
    static int check_edid(struct v4l2_subdev *sd, struct v4l2_subdev_edid *edid)

The above warnins happen because those functions are used only
when the V4L2 subdev API is enabled.
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Separate validation of different argument types. There's no reason to do
this separately for every IOCTL.
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Add the v4l2 core plumbing for the new VIDIOC_QUERY_EXT_CTRL ioctl.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

The subdev EDID ioctls receive a pad field that must reference an
existing pad and an EDID field that must point to a buffer. Validate
both fields in the core code instead of duplicating validation in all
drivers.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Validate the pad field in the core code whenever specified.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

VIDIOC_SUBDEV_[GS]_FRAME_INTERVAL IOCTLs argument structs contain the pad
field but the validity check was missing. There should be no implications
security-wise from this since no driver currently uses the pad field in the
struct.
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

Support this ioctl as part of the v4l2 core. Use the new ioctl
name and struct v4l2_edid type in the existing core 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>

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>

v4l2_subdev_link_validate_get_format() retrieves the remote pad format
depending on the entity type and prints a warning if the entity type is
not supported. The type check doesn't take the subtype into account, and
thus always prints a warning for device node types, even when supported.
Fix it.
Signed-off-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Currently, the v4l2 core is mixed together with other non-core drivers.
Move them into a separate directory.
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Change the users of V4L2_SUBDEV_SEL_TGT_* targets to use V4L2_SEL_TGT_*
instead. The common definitions are moved to a new header file,
include/linux/v4l2-common.h.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Acked-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

The string "_ACTUAL" does not say anything more about the target names. Drop
it. V4L2 selection API was changed by "V4L: Remove "_ACTIVE" from the
selection target name definitions" by Sylwester Nawrocki. This patch does
the same for the V4L2 subdev API.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

v4l2_subdev_link_validate() is the default op for validating a link. In V4L2
subdev context, it is used to call a pad op which performs the proper link
check without much extra work.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Fall back to s_selection if s_crop isn't implemented by a driver. Same for
g_selection / g_crop.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Add support for VIDIOC_SUBDEV_S_SELECTION and VIDIOC_SUBDEV_G_SELECTION
IOCTLs. They replace functionality provided by VIDIOC_SUBDEV_S_CROP and
VIDIOC_SUBDEV_G_CROP IOCTLs and also add new functionality (composing).

VIDIOC_SUBDEV_G_CROP and VIDIOC_SUBDEV_S_CROP continue to be supported.
Signed-off-by: NSakari Ailus <sakari.ailus@iki.fi>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

Add the start and end messages for log_status when called from a
subdev device node.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

The VIDIOC_LOG_STATUS ioctl allows to dump the current status of a driver
to the kernel log. Currently this ioctl is only available at video device
nodes and the subdevs rely on the host driver to expose their core.log_status
operation to user space.

This patch adds VIDIOC_LOG_STATUS support at the sub-device nodes,
for standalone subdevs that expose their own /dev entry.
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: NKyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

These two macros were in module.h but now module.h is no longer
sprayed across every source file imaginable, so the users need
to expicitly call out their use of them.
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

Ioctls on the subdevs node currently don't dispatch the register access debug
driver callbacks. Add the dispatching with the same security checks are for
non subdev video nodes (i.e. only capable(CAP_SYS_ADMIN may call the register
access ioctls).
Signed-off-by: NMartin Hostettler <martin@neutronstar.dyndns.org>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

The driver had to decide how many events to allocate when the v4l2_fh struct
was created. It was possible to add more events afterwards, but there was no
way to ensure that you wouldn't miss important events if the event queue
would fill up for that filehandle.

In addition, once there were no more free events, any new events were simply
dropped on the floor.

For the control event in particular this made life very difficult since
control status/value changes could just be missed if the number of allocated
events and the speed at which the application read events was too low to keep
up with the number of generated events. The application would have no idea
what the latest state was for a control since it could have missed the latest
control change.

So this patch makes some major changes in how events are allocated. Instead
of allocating events per-filehandle they are now allocated when subscribing an
event. So for that particular event type N events (determined by the driver)
are allocated. Those events are reserved for that particular event type.
This ensures that you will not miss events for a particular type altogether.

In addition, if there are N events in use and a new event is raised, then
the oldest event is dropped and the new one is added. So the latest event
is always available.

This can be further improved by adding the ability to merge the state of
two events together, ensuring that no data is lost at all. This will be
added in the next patch.

This also makes it possible to allow the user to determine the number of
events that will be allocated. This is not implemented at the moment, but
would be trivial.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>