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libcamera: Add support for V4L2 requests

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The V4L2 requests API provides support to atomically tie controls to a
set of buffers. This is especially common for m2m devices. Such a
request is represented by an fd that is allocated via
MEDIA_IOC_REQUEST_ALLOC and then passed to the various V4L2 functions.

Implement a V4L2Request class to wrap such an fd and add the
corresponding utility functions.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Stefan Klug
2025-11-25 17:28:15 +01:00
parent 39c052c1e9
commit cdc2620549
10 changed files with 269 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/libcamera/v4l2_device.cpp
+26 -5
View File
@@ -162,6 +162,7 @@ void V4L2Device::close()
/**
* \brief Read controls from the device
* \param[in] ids The list of controls to read, specified by their ID
* \param[in] request An optional request
*
* This function reads the value of all controls contained in \a ids, and
* returns their values as a ControlList.
@@ -171,10 +172,12 @@ void V4L2Device::close()
* during validation of the requested controls, no control is read and this
* function returns an empty control list.
*
* If \a request is specified the controls tied to that request are read.
*
* \return The control values in a ControlList on success, or an empty list on
* error
*/
ControlList V4L2Device::getControls(Span<const uint32_t> ids)
ControlList V4L2Device::getControls(Span<const uint32_t> ids, const V4L2Request *request)
{
if (ids.empty())
return {};
@@ -242,10 +245,16 @@ ControlList V4L2Device::getControls(Span<const uint32_t> ids)
}
struct v4l2_ext_controls v4l2ExtCtrls = {};
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
v4l2ExtCtrls.controls = v4l2Ctrls.data();
v4l2ExtCtrls.count = v4l2Ctrls.size();
if (request) {
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
v4l2ExtCtrls.request_fd = request->fd();
} else {
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
}
int ret = ioctl(VIDIOC_G_EXT_CTRLS, &v4l2ExtCtrls);
if (ret) {
unsigned int errorIdx = v4l2ExtCtrls.error_idx;
@@ -273,6 +282,7 @@ ControlList V4L2Device::getControls(Span<const uint32_t> ids)
/**
* \brief Write controls to the device
* \param[in] ctrls The list of controls to write
* \param[in] request An optional request
*
* This function writes the value of all controls contained in \a ctrls, and
* stores the values actually applied to the device in the corresponding
@@ -288,11 +298,16 @@ ControlList V4L2Device::getControls(Span<const uint32_t> ids)
* are written and their values are updated in \a ctrls, while all other
* controls are not written and their values are not changed.
*
* If \a request is set, the controls will be applied to that request. If the
* device doesn't support requests, -EACCESS will be returned. If \a request is
* invalid, -EINVAL will be returned.
*
* \return 0 on success or an error code otherwise
* \retval -EINVAL One of the control is not supported or not accessible
* \retval -EINVAL One of the controls is not supported or not accessible
* \retval -EACCESS The device does not support requests
* \retval i The index of the control that failed
*/
int V4L2Device::setControls(ControlList *ctrls)
int V4L2Device::setControls(ControlList *ctrls, const V4L2Request *request)
{
if (ctrls->empty())
return 0;
@@ -377,10 +392,16 @@ int V4L2Device::setControls(ControlList *ctrls)
}
struct v4l2_ext_controls v4l2ExtCtrls = {};
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
v4l2ExtCtrls.controls = v4l2Ctrls.data();
v4l2ExtCtrls.count = v4l2Ctrls.size();
if (request) {
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
v4l2ExtCtrls.request_fd = request->fd();
} else {
v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
}
int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
if (ret) {
unsigned int errorIdx = v4l2ExtCtrls.error_idx;