The V4L2_BUF_FLAG_NO_CACHE_INVALIDATE and V4L2_BUF_FLAG_NO_CACHE_CLEAN
buffer flags are currently not used by the kernel. Replace the definitions
by a single V4L2_BUF_FLAG_NO_CACHE_SYNC flag to be used by further
patches.
Different cache architectures should not be visible to the user space
which can make no meaningful use of the differences anyway. In case a
device can make use of non-coherent memory accesses, the necessary cache
operations depend on the CPU architecture and the buffer type, not the
requests of the user. The cache operation itself may be skipped on the
user's request which was the purpose of the two flags.
On ARM the invalidate and clean are separate operations whereas on
x86(-64) the two are a single operation (flush). Whether the hardware uses
the buffer for reading (V4L2_BUF_TYPE_*_OUTPUT*) or writing
(V4L2_BUF_TYPE_*CAPTURE*) already defines the required cache operation
(clean and invalidate, respectively). No user input is required.
Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
---
Documentation/DocBook/media/v4l/io.xml | 25 +++++++++++--------------
include/trace/events/v4l2.h | 3 +--
include/uapi/linux/videodev2.h | 7 +++++--
3 files changed, 17 insertions(+), 18 deletions(-)
diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
index 7bbc2a4..4facd63 100644
--- a/Documentation/DocBook/media/v4l/io.xml
+++ b/Documentation/DocBook/media/v4l/io.xml
@@ -1112,21 +1112,18 @@ application. Drivers set or clear this flag when the
linkend="vidioc-qbuf">VIDIOC_DQBUF</link> ioctl is called.</entry>
</row>
<row>
- <entry><constant>V4L2_BUF_FLAG_NO_CACHE_INVALIDATE</constant></entry>
+ <entry><constant>V4L2_BUF_FLAG_NO_CACHE_SYNC</constant></entry>
<entry>0x00000800</entry>
- <entry>Caches do not have to be invalidated for this buffer.
-Typically applications shall use this flag if the data captured in the buffer
-is not going to be touched by the CPU, instead the buffer will, probably, be
-passed on to a DMA-capable hardware unit for further processing or output.
-</entry>
- </row>
- <row>
- <entry><constant>V4L2_BUF_FLAG_NO_CACHE_CLEAN</constant></entry>
- <entry>0x00001000</entry>
- <entry>Caches do not have to be cleaned for this buffer.
-Typically applications shall use this flag for output buffers if the data
-in this buffer has not been created by the CPU but by some DMA-capable unit,
-in which case caches have not been used.</entry>
+ <entry>Do not perform CPU cache synchronisation operations
+ when the buffer is queued or dequeued. The user is
+ responsible for the correct use of this flag. It should be
+ only used when the buffer is not accessed using the CPU,
+ e.g. the buffer is written to by a hardware block and then
+ read by another one, in which case the flag should be set
+ in both <link linkend="vidioc-qbuf">VIDIOC_DQBUF</link>
+ and <link linkend="vidioc-qbuf">VIDIOC_QBUF</link> IOCTLs.
+ The flag has no effect on some devices / architectures.
+ </entry>
</row>
<row>
<entry><constant>V4L2_BUF_FLAG_LAST</constant></entry>
diff --git a/include/trace/events/v4l2.h b/include/trace/events/v4l2.h
index dbf017b..4cee91d 100644
--- a/include/trace/events/v4l2.h
+++ b/include/trace/events/v4l2.h
@@ -78,8 +78,7 @@ SHOW_FIELD
{ V4L2_BUF_FLAG_ERROR, "ERROR" }, \
{ V4L2_BUF_FLAG_TIMECODE, "TIMECODE" }, \
{ V4L2_BUF_FLAG_PREPARED, "PREPARED" }, \
- { V4L2_BUF_FLAG_NO_CACHE_INVALIDATE, "NO_CACHE_INVALIDATE" }, \
- { V4L2_BUF_FLAG_NO_CACHE_CLEAN, "NO_CACHE_CLEAN" }, \
+ { V4L2_BUF_FLAG_NO_CACHE_SYNC, "NO_CACHE_SYNC" }, \
{ V4L2_BUF_FLAG_TIMESTAMP_MASK, "TIMESTAMP_MASK" }, \
{ V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN, "TIMESTAMP_UNKNOWN" }, \
{ V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC, "TIMESTAMP_MONOTONIC" }, \
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 3228fbe..8d85aac 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -875,8 +875,11 @@ struct v4l2_buffer {
#define V4L2_BUF_FLAG_TIMECODE 0x00000100
/* Buffer is prepared for queuing */
#define V4L2_BUF_FLAG_PREPARED 0x00000400
-/* Cache handling flags */
-#define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE 0x00000800
+/* Cache sync hint */
+#define V4L2_BUF_FLAG_NO_CACHE_SYNC 0x00000800
+/* DEPRECATED. THIS WILL BE REMOVED IN THE FUTURE! */
+#define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE V4L2_BUF_FLAG_NO_CACHE_SYNC
+/* DEPRECATED. THIS WILL BE REMOVED IN THE FUTURE! */
#define V4L2_BUF_FLAG_NO_CACHE_CLEAN 0x00001000
/* Timestamp type */
#define V4L2_BUF_FLAG_TIMESTAMP_MASK 0x0000e000
--
2.1.0.231.g7484e3b
--
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