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Subject[PATCH v8 6/9] media: Add parsing for APP14 data segment in jpeg helpers
Date
From: Mirela Rabulea <mirela.rabulea@nxp.com>

According to Rec. ITU-T T.872 (06/2012) 6.5.3
APP14 segment is for color encoding, it contains a transform flag, which
may have values of 0, 1 and 2 and are interpreted as follows:
0 - CMYK for images that are encoded with four components
- RGB for images that are encoded with three components
1 - An image encoded with three components using YCbCr colour encoding.
2 - An image encoded with four components using YCCK colour encoding.

This is used in imx-jpeg decoder, to distinguish between
YUV444 and RGB24.

Signed-off-by: Mirela Rabulea <mirela.rabulea@nxp.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
---
Changes in v8:
Simplified end of jpeg_parse_app14_data, and added one more comment
Added Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/media/v4l2-core/v4l2-jpeg.c | 44 +++++++++++++++++++++++++++--
include/media/v4l2-jpeg.h | 20 +++++++++++++
2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-jpeg.c b/drivers/media/v4l2-core/v4l2-jpeg.c
index 8947fd95c6f1..ede40f2a5456 100644
--- a/drivers/media/v4l2-core/v4l2-jpeg.c
+++ b/drivers/media/v4l2-core/v4l2-jpeg.c
@@ -45,6 +45,7 @@ MODULE_LICENSE("GPL");
#define DHP 0xffde /* hierarchical progression */
#define EXP 0xffdf /* expand reference */
#define APP0 0xffe0 /* application data */
+#define APP14 0xffee /* application data for colour encoding */
#define APP15 0xffef
#define JPG0 0xfff0 /* extensions */
#define JPG13 0xfffd
@@ -444,8 +445,41 @@ static int jpeg_skip_segment(struct jpeg_stream *stream)
return jpeg_skip(stream, len - 2);
}

+/* Rec. ITU-T T.872 (06/2012) 6.5.3 */
+static int jpeg_parse_app14_data(struct jpeg_stream *stream,
+ enum v4l2_jpeg_app14_tf *tf)
+{
+ int ret;
+ int lp;
+ int skip;
+
+ lp = jpeg_get_word_be(stream);
+ if (lp < 0)
+ return lp;
+
+ /* Check for "Adobe\0" in Ap1..6 */
+ if (stream->curr + 6 > stream->end ||
+ strncmp(stream->curr, "Adobe\0", 6))
+ return -EINVAL;
+
+ /* get to Ap12 */
+ ret = jpeg_skip(stream, 11);
+ if (ret < 0)
+ return ret;
+
+ ret = jpeg_get_byte(stream);
+ if (ret < 0)
+ return ret;
+
+ *tf = ret;
+
+ /* skip the rest of the segment, this ensures at least it is complete */
+ skip = lp - 2 - 11;
+ return jpeg_skip(stream, skip);
+}
+
/**
- * jpeg_parse_header - locate marker segments and optionally parse headers
+ * v4l2_jpeg_parse_header - locate marker segments and optionally parse headers
* @buf: address of the JPEG buffer, should start with a SOI marker
* @len: length of the JPEG buffer
* @out: returns marker segment positions and optionally parsed headers
@@ -476,6 +510,9 @@ int v4l2_jpeg_parse_header(void *buf, size_t len, struct v4l2_jpeg_header *out)
if (marker != SOI)
return -EINVAL;

+ /* init value to signal if this marker is not present */
+ out->app14_tf = V4L2_JPEG_APP14_TF_UNKNOWN;
+
/* loop through marker segments */
while ((marker = jpeg_next_marker(&stream)) >= 0) {
switch (marker) {
@@ -519,7 +556,10 @@ int v4l2_jpeg_parse_header(void *buf, size_t len, struct v4l2_jpeg_header *out)
ret = jpeg_parse_restart_interval(&stream,
&out->restart_interval);
break;
-
+ case APP14:
+ ret = jpeg_parse_app14_data(&stream,
+ &out->app14_tf);
+ break;
case SOS:
ret = jpeg_reference_segment(&stream, &out->sos);
if (ret < 0)
diff --git a/include/media/v4l2-jpeg.h b/include/media/v4l2-jpeg.h
index ddba2a56c321..bae5a68bab6a 100644
--- a/include/media/v4l2-jpeg.h
+++ b/include/media/v4l2-jpeg.h
@@ -87,6 +87,24 @@ struct v4l2_jpeg_scan_header {
/* Ss, Se, Ah, and Al are not used by any driver */
};

+/**
+ * enum v4l2_jpeg_app14_tf - APP14 transform flag
+ * According to Rec. ITU-T T.872 (06/2012) 6.5.3
+ * APP14 segment is for color encoding, it contains a transform flag,
+ * which may have values of 0, 1 and 2 and are interpreted as follows:
+ * @V4L2_JPEG_APP14_TF_CMYK_RGB: CMYK for images encoded with four components
+ * RGB for images encoded with three components
+ * @V4L2_JPEG_APP14_TF_YCBCR: an image encoded with three components using YCbCr
+ * @V4L2_JPEG_APP14_TF_YCCK: an image encoded with four components using YCCK
+ * @V4L2_JPEG_APP14_TF_UNKNOWN: indicate app14 is not present
+ */
+enum v4l2_jpeg_app14_tf {
+ V4L2_JPEG_APP14_TF_CMYK_RGB = 0,
+ V4L2_JPEG_APP14_TF_YCBCR = 1,
+ V4L2_JPEG_APP14_TF_YCCK = 2,
+ V4L2_JPEG_APP14_TF_UNKNOWN = -1,
+};
+
/**
* struct v4l2_jpeg_header - parsed JPEG header
* @sof: pointer to frame header and size
@@ -100,6 +118,7 @@ struct v4l2_jpeg_scan_header {
* order, optional
* @restart_interval: number of MCU per restart interval, Ri
* @ecs_offset: buffer offset in bytes to the entropy coded segment
+ * @app14_tf: transform flag from app14 data
*
* When this structure is passed to v4l2_jpeg_parse_header, the optional scan,
* quantization_tables, and huffman_tables pointers must be initialized to NULL
@@ -119,6 +138,7 @@ struct v4l2_jpeg_header {
struct v4l2_jpeg_reference *huffman_tables;
u16 restart_interval;
size_t ecs_offset;
+ enum v4l2_jpeg_app14_tf app14_tf;
};

int v4l2_jpeg_parse_header(void *buf, size_t len, struct v4l2_jpeg_header *out);
--
2.25.1
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