linux-kernel - [PATCH RFT 5/7] media: hantro: jpeg: Add COM segment to JPEG header to align image scan

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Message-Id: <20211224084248.3070568-6-wenst@chromium.org>
Date:   Fri, 24 Dec 2021 16:42:46 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Chen-Yu Tsai <wenst@...omium.org>, linux-media@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: [PATCH RFT 5/7] media: hantro: jpeg: Add COM segment to JPEG header to align image scan

The JPEG header size is not 64-bit aligned. This makes the driver
require a bounce buffer for the encoded JPEG image scan output.

Add a COM (comment) segment to the JPEG header so that the header size
is a multiple of 64 bits. This will then allow dropping the use of the
bounce buffer, and instead have the hardware write out to the capture
buffer directly.

Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
---
 drivers/staging/media/hantro/hantro_jpeg.c | 3 +++
 drivers/staging/media/hantro/hantro_jpeg.h | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/media/hantro/hantro_jpeg.c b/drivers/staging/media/hantro/hantro_jpeg.c
index 7d4018bd6876..51e67e5cf86f 100644
--- a/drivers/staging/media/hantro/hantro_jpeg.c
+++ b/drivers/staging/media/hantro/hantro_jpeg.c
@@ -247,6 +247,9 @@ static const unsigned char hantro_jpeg_header[JPEG_HEADER_SIZE] = {
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
 
+	/* COM */
+	0xff, 0xfe, 0x00, 0x03, 0x00,
+
 	/* SOS */
 	0xff, 0xda, 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02,
 	0x11, 0x03, 0x11, 0x00, 0x3f, 0x00,
diff --git a/drivers/staging/media/hantro/hantro_jpeg.h b/drivers/staging/media/hantro/hantro_jpeg.h
index f33c492134e4..0b49d0b82caa 100644
--- a/drivers/staging/media/hantro/hantro_jpeg.h
+++ b/drivers/staging/media/hantro/hantro_jpeg.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0+ */
 
-#define JPEG_HEADER_SIZE	619
+#define JPEG_HEADER_SIZE	624
 #define JPEG_QUANT_SIZE		64
 
 struct hantro_jpeg_ctx {
-- 
2.34.1.448.ga2b2bfdf31-goog