[RFC PATCH v1] libcamera: pipeline: uvcvideo: Fix `ExposureTimeMode` control
Jacopo Mondi
jacopo.mondi at ideasonboard.com
Wed Jan 29 09:09:43 CET 2025
Hi Barnabas
On Tue, Jan 28, 2025 at 07:09:26PM +0000, Barnabás Pőcze wrote:
> Hi
>
>
> 2025. január 28., kedd 19:17 keltezéssel, Jacopo Mondi <jacopo.mondi at ideasonboard.com> írta:
>
> > Hi Barnabás
> >
> > On Tue, Jan 28, 2025 at 12:14:01PM +0000, Barnabás Pőcze wrote:
> > > `ControlInfo(Span<const int32_t>{...})` calls the incorrect constructor
> > > of `ControlInfo`. The intended constructor to be called is
> > > `ControlInfo(Span<const ControlValue>, ...)` however that is not called
> > > because a span of `const int32_t` is passed. Instead, the constructor
> > > `ControlInfo(const ControlValue &min, const ControlValue &max, ...)`
> > > will be called.
> >
> > So the two constructors your point our are
> >
> > ControlInfo::ControlInfo(const ControlValue &min,
> > const ControlValue &max,
> > const ControlValue &def)
> > : min_(min), max_(max), def_(def)
> > {
> > }
> >
> > ControlInfo::ControlInfo(const ControlValue &min,
> > const ControlValue &max,
> > const ControlValue &def)
> > : min_(min), max_(max), def_(def)
> > {
> > }
>
> I think you meant the following instead?
>
> ControlInfo::ControlInfo(Span<const ControlValue> values,
> const ControlValue &def)
> { ... }
>
>
Indeed, bad copy and paste, sorry
> >
> > right ?
> >
> >
> > And we call them with
> >
> > info = ControlInfo{Span<int32_t>{values}, values[0]};
> >
> > which, if I got you right gets expanded to
> >
> > ControlInfo::ControlInfo(const ControlValue &min, const ControlValue &max,
> > const ControlValue &def)
> >
> >
> > as int32_t are implicitly converted to ControlValue instances.
> >
> > As 'values' is declared as
> >
> > std::array<int32_t, 2> values{};
> >
> > I presume the intermediate call would look like
> >
> > ControlInfo(int32_t, int32_t, int32_t)
>
> ControlInfo(Span<const int32_t>, int32_t, int32_t)
How do we get from 2 parameters
ControlInfo{Span<int32_t>{values}, values[0]};
to three parameters ?
ControlInfo(Span<const int32_t>, int32_t, int32_t)
>
>
> >
> > and because of implicit conversion we get to
> >
> > ControlInfo(const ControlValue &min, const ControlValue &max,
> > const ControlValue &def)
> >
> > How come that, if I do (before this patch)
> >
> > - info = ControlInfo{Span<int32_t>{values}, values[0]};
> > + info = ControlInfo{Span<int32_t>{values}, values[0], values[0]};
> >
> > the code still compiles even if values is of size 2 ?
>
> As far as I can tell:
>
> * the second and third arguments (`values[0]`) will be converted to `ControlValue`
> using the following constructor:
>
> template<typename T, std::enable_if_t<!details::is_span<T>::value &&
> details::control_type<T>::value &&
> !std::is_same<std::string, std::remove_cv_t<T>>::value,
> std::nullptr_t> = nullptr>
> ControlValue(const T &value)
> : type_(ControlTypeNone), numElements_(0)
> {
> set(details::control_type<std::remove_cv_t<T>>::value, false,
> &value, 1, sizeof(T));
> }
>
>
> * the first argument, the span of `const int32_t` will be converted to `ControlValue`
> using the following constructor:
>
> template<typename T, std::enable_if_t<details::is_span<T>::value ||
> std::is_same<std::string, std::remove_cv_t<T>>::value,
> std::nullptr_t> = nullptr>
> ControlValue(const T &value)
> : type_(ControlTypeNone), numElements_(0)
> {
> set(details::control_type<std::remove_cv_t<T>>::value, true,
> value.data(), value.size(), sizeof(typename T::value_type));
> }
>
> The resulting `ControlInfo` is nonetheless of questionable usefulness as the
> types of min/max/def will not be the same, but this is probably expected by
> users.
>
Agreed, just trying to get to the details and see how we can avoid
this from happening generically
>
> >
> > >
> > > To fix this, simply pass a span of `ControlValue` instead.
> > >
> > > Furthermore, the mapping in `UVCCameraData::processControl()` is also not
> > > entirely correct because the control value is retrieved as a `bool`
> > > instead of - the correct type - `int32_t`. Additionally, the available
> > > modes are not taken into account.
> >
> > Please split this to a different patch. And in any case, but I have to
> > re-check, I think the ControlValidator makes sure the control set by
> > the applications on a camera are supported.
>
> Sorry, what I meant is that it was not taken into account which of the
> `V4L2_EXPOSURE_*` modes are supported. The code unconditionally used
> `V4L2_EXPOSURE_{MANUAL,APERTURE_PRIORITY}`. Is there something I am missing?
No, I thought CameraControlValidator::validate() was making sure the
ControlValue provided along with the ControlId to ControlList::set()
was valid against the ControlInfo values, but it only makes sure the
id is valid
bool CameraControlValidator::validate(unsigned int id) const
{
const ControlInfoMap &controls = camera_->controls();
return controls.find(id) != controls.end();
}
Maybe this is the right level at which this kind of check should be
performed instead of doing so in each single pipeline handler ?
Have you considered that ?
>
>
> >
> > >
> > > To fix this, stores the available modes for `V4L2_CID_EXPOSURE_AUTO`
> > > and select the appropriate mode based on the mapping established
> > > in the comment.
> > >
> > > Fixes: bad8d591f8acfa ("libcamera: uvcvideo: Register ExposureTimeMode control")
> > > Signed-off-by: Barnabás Pőcze <pobrn at protonmail.com>
> > > ---
> > > src/libcamera/pipeline/uvcvideo/uvcvideo.cpp | 81 +++++++++++++-------
> > > 1 file changed, 53 insertions(+), 28 deletions(-)
> > >
> > > diff --git a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > index dedcac89b..7821cceb0 100644
> > > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > > @@ -6,6 +6,7 @@
> > > */
> > >
> > > #include <algorithm>
> > > +#include <bitset>
> > > #include <cmath>
> > > #include <fstream>
> > > #include <map>
> > > @@ -58,6 +59,13 @@ public:
> > > Stream stream_;
> > > std::map<PixelFormat, std::vector<SizeRange>> formats_;
> > >
> > > + std::bitset<std::max({
> > > + V4L2_EXPOSURE_AUTO,
> > > + V4L2_EXPOSURE_MANUAL,
> > > + V4L2_EXPOSURE_APERTURE_PRIORITY,
> > > + V4L2_EXPOSURE_SHUTTER_PRIORITY,
> > > + }) + 1> availableExposureModes_;
> > > +
> > > private:
> > > bool generateId();
> > >
> > > @@ -95,8 +103,8 @@ public:
> > > bool match(DeviceEnumerator *enumerator) override;
> > >
> > > private:
> > > - int processControl(ControlList *controls, unsigned int id,
> > > - const ControlValue &value);
> > > + int processControl(UVCCameraData *data, ControlList *controls,
> > > + unsigned int id, const ControlValue &value);
> > > int processControls(UVCCameraData *data, Request *request);
> > >
> > > bool acquireDevice(Camera *camera) override;
> > > @@ -289,8 +297,8 @@ void PipelineHandlerUVC::stopDevice(Camera *camera)
> > > data->video_->releaseBuffers();
> > > }
> > >
> > > -int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
> > > - const ControlValue &value)
> > > +int PipelineHandlerUVC::processControl(UVCCameraData *data, ControlList *controls,
> > > + unsigned int id, const ControlValue &value)
> > > {
> > > uint32_t cid;
> > >
> > > @@ -334,10 +342,27 @@ int PipelineHandlerUVC::processControl(ControlList *controls, unsigned int id,
> > > }
> > >
> > > case V4L2_CID_EXPOSURE_AUTO: {
> > > - int32_t ivalue = value.get<bool>()
> > > - ? V4L2_EXPOSURE_APERTURE_PRIORITY
> > > - : V4L2_EXPOSURE_MANUAL;
> > > - controls->set(V4L2_CID_EXPOSURE_AUTO, ivalue);
> > > + switch (value.get<int32_t>()) {
> > > + case controls::ExposureTimeModeAuto:
> > > + if (data->availableExposureModes_[V4L2_EXPOSURE_AUTO])
> > > + controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_AUTO);
> > > + else if (data->availableExposureModes_[V4L2_EXPOSURE_APERTURE_PRIORITY])
> > > + controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_APERTURE_PRIORITY);
> > > + else
> > > + ASSERT(false);
> > > + break;
> > > + case controls::ExposureTimeModeManual:
> > > + if (data->availableExposureModes_[V4L2_EXPOSURE_MANUAL])
> > > + controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_MANUAL);
> > > + else if (data->availableExposureModes_[V4L2_EXPOSURE_SHUTTER_PRIORITY])
> > > + controls->set(V4L2_CID_EXPOSURE_AUTO, V4L2_EXPOSURE_SHUTTER_PRIORITY);
> > > + else
> > > + ASSERT(false);
> > > + break;
> > > + default:
> > > + ASSERT(false);
> > > + break;
> > > + }
> > > break;
> > > }
> > >
> > > @@ -375,7 +400,7 @@ int PipelineHandlerUVC::processControls(UVCCameraData *data, Request *request)
> > > ControlList controls(data->video_->controls());
> > >
> > > for (const auto &[id, value] : request->controls())
> > > - processControl(&controls, id, value);
> > > + processControl(data, &controls, id, value);
> > >
> > > for (const auto &ctrl : controls)
> > > LOG(UVC, Debug)
> > > @@ -725,25 +750,25 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
> > > * ExposureTimeModeManual = { V4L2_EXPOSURE_MANUAL,
> > > * V4L2_EXPOSURE_SHUTTER_PRIORITY }
> > > */
> > > - std::array<int32_t, 2> values{};
> > > -
> > > - auto it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> > > - [&](const ControlValue &val) {
> > > - return (val.get<int32_t>() == V4L2_EXPOSURE_APERTURE_PRIORITY ||
> > > - val.get<int32_t>() == V4L2_EXPOSURE_AUTO) ? true : false;
> > > - });
> > > - if (it != v4l2Values.end())
> > > - values.back() = static_cast<int32_t>(controls::ExposureTimeModeAuto);
> > > -
> > > - it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> > > - [&](const ControlValue &val) {
> > > - return (val.get<int32_t>() == V4L2_EXPOSURE_SHUTTER_PRIORITY ||
> > > - val.get<int32_t>() == V4L2_EXPOSURE_MANUAL) ? true : false;
> > > - });
> > > - if (it != v4l2Values.end())
> > > - values.back() = static_cast<int32_t>(controls::ExposureTimeModeManual);
> > > -
> > > - info = ControlInfo{Span<int32_t>{values}, values[0]};
> > > + for (const ControlValue &value : v4l2Values) {
> > > + auto x = value.get<int32_t>();
> > > + if (0 <= x && size_t(x) < availableExposureModes_.size())
> > > + availableExposureModes_[x] = true;
> > > + }
> > > +
> > > + std::array<ControlValue, 2> values;
> > > + std::size_t count = 0;
> > > +
> > > + if (availableExposureModes_[V4L2_EXPOSURE_AUTO] || availableExposureModes_[V4L2_EXPOSURE_APERTURE_PRIORITY])
> > > + values[count++] = controls::ExposureTimeModeAuto;
> > > +
> > > + if (availableExposureModes_[V4L2_EXPOSURE_MANUAL] || availableExposureModes_[V4L2_EXPOSURE_SHUTTER_PRIORITY])
> > > + values[count++] = controls::ExposureTimeModeManual;
> > > +
> > > + if (count == 0)
> > > + return;
> > > +
> > > + info = ControlInfo{Span<const ControlValue>{ values.data(), count }, values[0]};
> >
> > isn't this simpler ?
> >
> > --- a/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > +++ b/src/libcamera/pipeline/uvcvideo/uvcvideo.cpp
> > @@ -723,7 +723,7 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
> > * ExposureTimeModeManual = { V4L2_EXPOSURE_MANUAL,
> > * V4L2_EXPOSURE_SHUTTER_PRIORITY }
> > */
> > - std::array<int32_t, 2> values{};
> > + std::array<ControlValue, 2> values{};
> >
> > auto it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> > [&](const ControlValue &val) {
> > @@ -731,7 +731,7 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
> > val.get<int32_t>() == V4L2_EXPOSURE_AUTO) ? true : false;
> > });
> > if (it != v4l2Values.end())
> > - values.back() = static_cast<int32_t>(controls::ExposureTimeModeAuto);
> > + values.back() = controls::ExposureTimeModeAuto;
> >
> > it = std::find_if(v4l2Values.begin(), v4l2Values.end(),
> > [&](const ControlValue &val) {
> > @@ -739,9 +739,9 @@ void UVCCameraData::addControl(uint32_t cid, const ControlInfo &v4l2Info,
> > val.get<int32_t>() == V4L2_EXPOSURE_MANUAL) ? true : false;
> > });
> > if (it != v4l2Values.end())
> > - values.back() = static_cast<int32_t>(controls::ExposureTimeModeManual);
> > + values.back() = controls::ExposureTimeModeManual;
> >
> > - info = ControlInfo{Span<int32_t>{values}, values[0]};
> > + info = ControlInfo{Span<const ControlValue>{values}, values[0]};
> > break;
> > }
> > case V4L2_CID_EXPOSURE_ABSOLUTE:
> >
>
> See my comment above, the `availableExposureModes_` is needed later in `processControl()`
Yes, later :) I'm still leaning towards "two issues, two patches" even
if the second one builds on the former.
> to determine which of the `V4L2_EXPOSURE_*` value to use. So this approach
> seemed simplest since the `availableExposureModes_` bitset has to be calculated
> either way. Also, the above change always sets `values[1]`.
Right, that's another issue, even more so if the camera does not
report any exposure related controls, in this case even values[0]
won't be valid.
How is
Span<const ControlValue>{values}
constructed ?
If I read
template<std::size_t N>
constexpr Span(const std::array<value_type, N> &arr,
std::enable_if_t<std::is_convertible<std::remove_pointer_t<decltype(utils::data(arr))> (*)[],
element_type (*)[]>::value &&
N == Extent,
std::nullptr_t> = nullptr) noexcept
: data_(arr.data())
{
}
right the span<> will have the same size as the array fixed size (2 in
this case) regardless of how many elements have actually been
populated.
>
>
> > > break;
> > > }
> > > case V4L2_CID_EXPOSURE_ABSOLUTE:
> > > --
> > > 2.48.1
> > >
> > >
> >
>
>
> Regards,
> Barnabás Pőcze
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