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From: Ricardo Ribalda <ribalda@chromium.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	 Mauro Carvalho Chehab <mchehab@kernel.org>,
	 Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>,
	 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	 Hans de Goede <hansg@kernel.org>,
	Hans de Goede <hansg@kernel.org>
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	 linux-usb@vger.kernel.org,
	Ricardo Ribalda <ribalda@chromium.org>
Subject: [PATCH v8 2/5] media: Documentation: Add note about UVCH length field
Date: Mon, 07 Jul 2025 18:34:02 +0000	[thread overview]
Message-ID: <20250707-uvc-meta-v8-2-ed17f8b1218b@chromium.org> (raw)
In-Reply-To: <20250707-uvc-meta-v8-0-ed17f8b1218b@chromium.org>

The documentation currently describes the UVC length field as the "length
of the rest of the block", which can be misleading. The driver limits the
data copied to a maximum of 12 bytes.

This change adds a clarifying sentence to the documentation to make this
restriction explicit.

Reviewed-by: Hans de Goede <hansg@kernel.org>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 Documentation/userspace-api/media/v4l/metafmt-uvc.rst | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/userspace-api/media/v4l/metafmt-uvc.rst b/Documentation/userspace-api/media/v4l/metafmt-uvc.rst
index 784346d14bbdbf28348262084d5b0646d30bd1da..4c05e9e54683a2bf844ddf26f99d0d9713ef05de 100644
--- a/Documentation/userspace-api/media/v4l/metafmt-uvc.rst
+++ b/Documentation/userspace-api/media/v4l/metafmt-uvc.rst
@@ -44,7 +44,9 @@ Each individual block contains the following fields:
         them
     * - :cspan:`1` *The rest is an exact copy of the UVC payload header:*
     * - __u8 length;
-      - length of the rest of the block, including this field
+      - length of the rest of the block, including this field. Please note that
+        regardless of this value, for V4L2_META_FMT_UVC the kernel will never
+        copy more than 2-12 bytes.
     * - __u8 flags;
       - Flags, indicating presence of other standard UVC fields
     * - __u8 buf[];

-- 
2.50.0.727.gbf7dc18ff4-goog


  parent reply	other threads:[~2025-07-07 18:34 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-07-07 18:34 [PATCH v8 0/5] media: uvcvideo: Introduce V4L2_META_FMT_UVC_MSXU_1_5 + other meta fixes Ricardo Ribalda
2025-07-07 18:34 ` [PATCH v8 1/5] media: uvcvideo: Do not mark valid metadata as invalid Ricardo Ribalda
2025-07-07 18:34 ` Ricardo Ribalda [this message]
2025-07-07 18:34 ` [PATCH v8 3/5] media: uvcvideo: Introduce dev->meta_formats Ricardo Ribalda
2025-07-07 20:55   ` Hans de Goede
2025-07-07 18:34 ` [PATCH v8 4/5] media: uvcvideo: Introduce V4L2_META_FMT_UVC_MSXU_1_5 Ricardo Ribalda
2025-07-11 20:13   ` Laurent Pinchart
2025-07-14  7:44     ` Ricardo Ribalda
2025-07-14 14:59   ` Laurent Pinchart
2025-07-14 16:21     ` Ricardo Ribalda
2025-07-14 16:27       ` Laurent Pinchart
2025-07-14 16:42         ` Ricardo Ribalda
2025-07-14 17:07           ` Laurent Pinchart
2025-07-14 17:32             ` Ricardo Ribalda
2025-07-07 18:34 ` [PATCH v8 5/5] media: uvcvideo: Auto-set UVC_QUIRK_MSXU_META Ricardo Ribalda
2025-07-11 19:58   ` Laurent Pinchart
2025-07-14  7:46     ` Ricardo Ribalda
2025-07-14  8:06       ` Laurent Pinchart
2025-07-14  8:21         ` Ricardo Ribalda
2025-07-14  8:34           ` Laurent Pinchart
2025-07-07 21:00 ` [PATCH v8 0/5] media: uvcvideo: Introduce V4L2_META_FMT_UVC_MSXU_1_5 + other meta fixes Hans de Goede

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