linux-kernel - [PATCH v6 8/9] media: Avoid parsing quantization and huffman tables

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Date:   Tue, 15 Dec 2020 13:18:42 +0200
From:   "Mirela Rabulea (OSS)" <mirela.rabulea@....nxp.com>
To:     mchehab@...nel.org, hverkuil-cisco@...all.nl, shawnguo@...nel.org,
        robh+dt@...nel.org, p.zabel@...gutronix.de
Cc:     paul.kocialkowski@...tlin.com, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-imx@....com,
        s.hauer@...gutronix.de, aisheng.dong@....com,
        daniel.baluta@....com, robert.chiras@....com,
        laurentiu.palcu@....com, mark.rutland@....com,
        devicetree@...r.kernel.org, ezequiel@...labora.com,
        laurent.pinchart+renesas@...asonboard.com,
        niklas.soderlund+renesas@...natech.se,
        dafna.hirschfeld@...labora.com,
        Mirela Rabulea <mirela.rabulea@....com>
Subject: [PATCH v6 8/9] media: Avoid parsing quantization and huffman tables

From: Mirela Rabulea <mirela.rabulea@....com>

These are optional in struct v4l2_jpeg_header, so skip DHT/DQT segment
parsing if huffman_tables/quantization_tables were not requested by user,
to save time.
However, do count them (num_dht/num_dqt).

Signed-off-by: Mirela Rabulea <mirela.rabulea@....com>
---
Changes in v6:
  Call jpeg_skip_segment() instead of jpeg_parse_quantization_table()/jpeg_parse_huffman_tables(),
  when quantization/huffman tables are not requested by user.
  Remove the NULL pointer check in the lower-level function.
  Thanks Philipp & Hans for feedback

 drivers/media/v4l2-core/v4l2-jpeg.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-jpeg.c b/drivers/media/v4l2-core/v4l2-jpeg.c
index dc9def4c2648..f3d03d39defb 100644
--- a/drivers/media/v4l2-core/v4l2-jpeg.c
+++ b/drivers/media/v4l2-core/v4l2-jpeg.c
@@ -537,6 +537,10 @@ int v4l2_jpeg_parse_header(void *buf, size_t len, struct v4l2_jpeg_header *out)
 					&out->dht[out->num_dht++ % 4]);
 			if (ret < 0)
 				return ret;
+			if (!out->huffman_tables) {
+				ret = jpeg_skip_segment(&stream);
+				break;
+			}
 			ret = jpeg_parse_huffman_tables(&stream,
 							out->huffman_tables);
 			break;
@@ -545,6 +549,10 @@ int v4l2_jpeg_parse_header(void *buf, size_t len, struct v4l2_jpeg_header *out)
 					&out->dqt[out->num_dqt++ % 4]);
 			if (ret < 0)
 				return ret;
+			if (!out->quantization_tables) {
+				ret = jpeg_skip_segment(&stream);
+				break;
+			}
 			ret = jpeg_parse_quantization_tables(&stream,
 					out->frame.precision,
 					out->quantization_tables);
-- 
2.17.1