[PATCH v8 6/9] media: Add parsing for APP14 data segment in jpeg helpers

[Mirela Rabulea]

From: Mirela Rabulea <mirela.rabulea@xxxxxxx>

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@xxxxxxx>
Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
Changes in v8:
  Simplified end of jpeg_parse_app14_data, and added one more comment
  Added Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>

 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