On Mon, 2021-01-11 at 21:28 +0200, Mirela Rabulea wrote:
> 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>
> ---
> Changes in v7:
> Check there are 6 bytes available in the stream before checking for "Adobe\0"
> Change jpeg_parse_app14_data function to differentiate between the 3 scenarios: app14 missing, or app14 present but with/without parsing errors:
> App14 missing => Added V4L2_JPEG_APP14_TF_UNKNOWN to the enum v4l2_jpeg_app14_tf, use it to indicate app14 & TF is missing
> App14 present without parsing errors => Return the transform flag value as enum v4l2_jpeg_app14_tf (new paramater of jpeg_parse_app14_data function)
> App14 present with parsing errors => Return -EINVAL from jpeg_parse_app14_data, also return from calling function (v4l2_jpeg_parse_header) when this error is met.
>
> drivers/media/v4l2-core/v4l2-jpeg.c | 47 +++++++++++++++++++++++++++--
> include/media/v4l2-jpeg.h | 20 ++++++++++++
> 2 files changed, 65 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-jpeg.c b/drivers/media/v4l2-core/v4l2-jpeg.c
> index 8947fd95c6f1..8d5fedb136dd 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 +445,44 @@ 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 = lp - 2 - 11;
> + ret = jpeg_skip(stream, skip);
> + if (ret < 0)
> + return ret;
> +
> + return 0;
This could be simplified to
return jpeg_skip(stream, skip);
although it would be better style to move the *tf = ... assignment down
past the last error return instead. Either way,
Reviewed-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
regards
Philipp
