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This read-only control allows applications to query the total amount of memory currently used by a device instance. The documentation explains: - The control reports memory usage in bytes for driver-managed allocations - It includes internal buffers, intermediate processing data, and other driver allocations associated with the instance - Applications can use it for debugging, resource monitoring, and making informed buffer allocation decisions - The value may change dynamically during device operation - It only reports driver-managed memory, not application-allocated buffers Update V4L2_CID_LASTP1 definition to reflect the new control as the last predefined control ID. Signed-off-by: Ming Qian --- .../userspace-api/media/v4l/control.rst | 22 ++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/Documentation/userspace-api/media/v4l/control.rst b/Documentation/userspace-api/media/v4l/control.rst index 19372bb32c4b..6904c5bdbf37 100644 --- a/Documentation/userspace-api/media/v4l/control.rst +++ b/Documentation/userspace-api/media/v4l/control.rst @@ -316,9 +316,29 @@ Control IDs set the alpha component value of all pixels for further processing in the device. +``V4L2_CID_MEMORY_USAGE`` ``(integer64)`` + This is an optional read-only control that reports the total amount of + memory, in bytes, currently allocated and used by this device instance. + This includes memory used for internal buffers, intermediate processing + data, and any other driver-managed allocations associated with the + instance. + + Applications can use this control to monitor memory consumption for + debugging purposes, resource management, or to make informed decisions + about buffer allocation strategies. The value may change dynamically + as the device operates, for example when buffers are allocated or + released during streaming. + + Note that this control only reports memory managed by the driver for + this specific instance; it does not include memory allocated by the + application itself (e.g., userspace buffers passed to the driver). + + Not all drivers support this control. Applications should query for + its availability before use. + ``V4L2_CID_LASTP1`` End of the predefined control IDs (currently - ``V4L2_CID_ALPHA_COMPONENT`` + 1). + ``V4L2_CID_MEMORY_USAGE`` + 1). ``V4L2_CID_PRIVATE_BASE`` ID of the first custom (driver specific) control. Applications -- 2.53.0