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[34.88.141.166]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-556383d31a6sm1417630e87.61.2025.07.07.11.34.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Jul 2025 11:34:03 -0700 (PDT) From: Ricardo Ribalda Date: Mon, 07 Jul 2025 18:34:02 +0000 Subject: [PATCH v8 2/5] media: Documentation: Add note about UVCH length field Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250707-uvc-meta-v8-2-ed17f8b1218b@chromium.org> References: <20250707-uvc-meta-v8-0-ed17f8b1218b@chromium.org> In-Reply-To: <20250707-uvc-meta-v8-0-ed17f8b1218b@chromium.org> To: Laurent Pinchart , Mauro Carvalho Chehab , Guennadi Liakhovetski , Greg Kroah-Hartman , Hans de Goede , Hans de Goede Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, Ricardo Ribalda X-Mailer: b4 0.14.2 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 Signed-off-by: Ricardo Ribalda --- 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