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libcamera: v4l2_device: Workaround faulty control menus

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Some UVC cameras have been identified that can provide V4L2 menu
controls without any menu items.

This leads to a segfault where we try to construct a
ControlInfo(Span<>,default) with an empty span.

Convert the v4l2ControlInfo and v4l2MenuControlInfo helper functions to
return std::optional<ControlInfo> to be able to account in the caller if
the control is valid, and only add acceptable controls to the supported
control list.

Menu controls without a list of menu items are no longer added as a
valid control and a warning is logged.

This also fixes a potential crash that would have occured in the
unlikely event that a ctrl.minimum was set to less than 0.

Bug: https://bugs.libcamera.org/show_bug.cgi?id=167
Reported-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
This commit is contained in:
Kieran Bingham 2022-11-01 18:00:51 +00:00
parent 1cd7646f97
commit 96ed45b971
2 changed files with 25 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/libcamera/internal/v4l2_device.h
View file

@ -70,8 +70,8 @@ protected:
private:
static ControlType v4l2CtrlType(uint32_t ctrlType);
static std::unique_ptr<ControlId> v4l2ControlId(const v4l2_query_ext_ctrl &ctrl);
ControlInfo v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl);
ControlInfo v4l2MenuControlInfo(const v4l2_query_ext_ctrl &ctrl);
std::optional<ControlInfo> v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl);
std::optional<ControlInfo> v4l2MenuControlInfo(const v4l2_query_ext_ctrl &ctrl);
void listControls();
void updateControls(ControlList *ctrls,

28
src/libcamera/v4l2_device.cpp
View file

@ -529,7 +529,7 @@ std::unique_ptr<ControlId> V4L2Device::v4l2ControlId(const v4l2_query_ext_ctrl &
* \param[in] ctrl The v4l2_query_ext_ctrl that represents a V4L2 control
* \return A ControlInfo that represents \a ctrl
*/
ControlInfo V4L2Device::v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl)
std::optional<ControlInfo> V4L2Device::v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl)
{
switch (ctrl.type) {
case V4L2_CTRL_TYPE_U8:
@ -566,14 +566,14 @@ ControlInfo V4L2Device::v4l2ControlInfo(const v4l2_query_ext_ctrl &ctrl)
*
* \return A ControlInfo that represents \a ctrl
*/
ControlInfo V4L2Device::v4l2MenuControlInfo(const struct v4l2_query_ext_ctrl &ctrl)
std::optional<ControlInfo> V4L2Device::v4l2MenuControlInfo(const struct v4l2_query_ext_ctrl &ctrl)
{
std::vector<ControlValue> indices;
struct v4l2_querymenu menu = {};
menu.id = ctrl.id;
if (ctrl.minimum < 0)
return ControlInfo();
return std::nullopt;
for (int32_t index = ctrl.minimum; index <= ctrl.maximum; ++index) {
menu.index = index;
@ -583,6 +583,14 @@ ControlInfo V4L2Device::v4l2MenuControlInfo(const struct v4l2_query_ext_ctrl &ct
indices.push_back(index);
}
/*
* Some faulty UVC devices are known to return an empty menu control.
* Controls without a menu option can not be set, or read, so they are
* not exposed.
*/
if (indices.size() == 0)
return std::nullopt;
return ControlInfo(indices,
ControlValue(static_cast<int32_t>(ctrl.default_value)));
}
@ -631,7 +639,17 @@ void V4L2Device::listControls()
controlIdMap_[ctrl.id] = controlIds_.back().get();
controlInfo_.emplace(ctrl.id, ctrl);
ctrls.emplace(controlIds_.back().get(), v4l2ControlInfo(ctrl));
std::optional<ControlInfo> info = v4l2ControlInfo(ctrl);
if (!info) {
LOG(V4L2, Error)
<< "Control " << ctrl.name
<< " cannot be registered";
continue;
}
ctrls.emplace(controlIds_.back().get(), *info);
}
controls_ = ControlInfoMap(std::move(ctrls), controlIdMap_);
@ -670,7 +688,7 @@ void V4L2Device::updateControlInfo()
continue;
}
info = v4l2ControlInfo(ctrl);
info = *v4l2ControlInfo(ctrl);
}
}