[libcamera-devel,v2,2/3] libcamera: V4L2Device: Use std::vector for v4l2_ext_control in setControls()
diff mbox series

Message ID 20210415044854.3348529-2-hiroh@chromium.org
State Changes Requested
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Series
  • [libcamera-devel,v2,1/3] libcamera: V4L2Device: Use std::vector for v4l2_ext_control in getControls()
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Commit Message

Hirokazu Honda April 15, 2021, 4:48 a.m. UTC 
The original code uses Variable-Length-Array, which is not
officially supported in C++. This replaces the array with
std::vector.

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/libcamera/v4l2_device.cpp | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

Comments

Laurent Pinchart April 20, 2021, 1:15 a.m. UTC | #1 
Hi Hiro,

Thank you for the patch.

On Thu, Apr 15, 2021 at 01:48:53PM +0900, Hirokazu Honda wrote:
> The original code uses Variable-Length-Array, which is not
> officially supported in C++. This replaces the array with
> std::vector.
> 
> Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/libcamera/v4l2_device.cpp | 32 +++++++++++++++-----------------
>  1 file changed, 15 insertions(+), 17 deletions(-)
> 
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index ee8c3fed..5ec1b10e 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -279,12 +279,11 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
>   */
>  int V4L2Device::setControls(ControlList *ctrls)
>  {
> -	unsigned int count = ctrls->size();
> -	if (count == 0)
> +	if (ctrls->empty())
>  		return 0;
>  
> -	struct v4l2_ext_control v4l2Ctrls[count];
> -	memset(v4l2Ctrls, 0, sizeof(v4l2Ctrls));
> +	std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size());
> +	memset(v4l2Ctrls.data(), 0, v4l2Ctrls.size());

Is the memset() needed ? The std::vector constructor will default-insert
the elements, which value-initializes them. If my interpretation of
https://en.cppreference.com/w/cpp/language/value_initialization is
correct, the elements will be zero-initialized.

>  
>  	unsigned int i = 0;

Should we replace i with

	v4l2_ext_control *v4l2Ctrl = v4l2Ctrls.data();

and do a

	v4l2Ctrl++;

at the end of the loop ? That way we would ensure that i won't be used
incorrectly (after being incremented) inside the loop.

Apart from that,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  	for (auto &ctrl : *ctrls) {
> @@ -295,14 +294,14 @@ int V4L2Device::setControls(ControlList *ctrls)
>  				<< "Control " << utils::hex(id) << " not found";
>  			return -EINVAL;
>  		}
> -
> -		v4l2Ctrls[i].id = id;
> +		v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
> +		v4l2Ctrl.id = id;
>  
>  		/* Set the v4l2_ext_control value for the write operation. */
>  		ControlValue &value = ctrl.second;
>  		switch (iter->first->type()) {
>  		case ControlTypeInteger64:
> -			v4l2Ctrls[i].value64 = value.get<int64_t>();
> +			v4l2Ctrl.value64 = value.get<int64_t>();
>  			break;
>  
>  		case ControlTypeByte: {
> @@ -314,32 +313,30 @@ int V4L2Device::setControls(ControlList *ctrls)
>  			}
>  
>  			Span<uint8_t> data = value.data();
> -			v4l2Ctrls[i].p_u8 = data.data();
> -			v4l2Ctrls[i].size = data.size();
> +			v4l2Ctrl.p_u8 = data.data();
> +			v4l2Ctrl.size = data.size();
>  
>  			break;
>  		}
>  
>  		default:
>  			/* \todo To be changed to support strings. */
> -			v4l2Ctrls[i].value = value.get<int32_t>();
> +			v4l2Ctrl.value = value.get<int32_t>();
>  			break;
>  		}
> -
> -		i++;
>  	}
>  
>  	struct v4l2_ext_controls v4l2ExtCtrls = {};
>  	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
> -	v4l2ExtCtrls.controls = v4l2Ctrls;
> -	v4l2ExtCtrls.count = count;
> +	v4l2ExtCtrls.controls = v4l2Ctrls.data();
> +	v4l2ExtCtrls.count = v4l2Ctrls.size();
>  
>  	int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
>  	if (ret) {
>  		unsigned int errorIdx = v4l2ExtCtrls.error_idx;
>  
>  		/* Generic validation error. */
> -		if (errorIdx == 0 || errorIdx >= count) {
> +		if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
>  			LOG(V4L2, Error) << "Unable to set controls: "
>  					 << strerror(-ret);
>  			return -EINVAL;
> @@ -348,11 +345,12 @@ int V4L2Device::setControls(ControlList *ctrls)
>  		/* A specific control failed. */
>  		LOG(V4L2, Error) << "Unable to set control " << errorIdx
>  				 << ": " << strerror(-ret);
> -		count = errorIdx - 1;
> +
> +		v4l2Ctrls.resize(errorIdx);
>  		ret = errorIdx;
>  	}
>  
> -	updateControls(ctrls, v4l2Ctrls, count);
> +	updateControls(ctrls, v4l2Ctrls.data(), v4l2Ctrls.size());
>  
>  	return ret;
>  }
Hirokazu Honda April 21, 2021, 9:30 a.m. UTC | #2 
Hi Laurent, thanks for reviewing.

On Tue, Apr 20, 2021 at 10:15 AM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Hiro,
>
> Thank you for the patch.
>
> On Thu, Apr 15, 2021 at 01:48:53PM +0900, Hirokazu Honda wrote:
> > The original code uses Variable-Length-Array, which is not
> > officially supported in C++. This replaces the array with
> > std::vector.
> >
> > Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
> > Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > ---
> >  src/libcamera/v4l2_device.cpp | 32 +++++++++++++++-----------------
> >  1 file changed, 15 insertions(+), 17 deletions(-)
> >
> > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > index ee8c3fed..5ec1b10e 100644
> > --- a/src/libcamera/v4l2_device.cpp
> > +++ b/src/libcamera/v4l2_device.cpp
> > @@ -279,12 +279,11 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
> >   */
> >  int V4L2Device::setControls(ControlList *ctrls)
> >  {
> > -     unsigned int count = ctrls->size();
> > -     if (count == 0)
> > +     if (ctrls->empty())
> >               return 0;
> >
> > -     struct v4l2_ext_control v4l2Ctrls[count];
> > -     memset(v4l2Ctrls, 0, sizeof(v4l2Ctrls));
> > +     std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size());
> > +     memset(v4l2Ctrls.data(), 0, v4l2Ctrls.size());
>
> Is the memset() needed ? The std::vector constructor will default-insert
> the elements, which value-initializes them. If my interpretation of
> https://en.cppreference.com/w/cpp/language/value_initialization is
> correct, the elements will be zero-initialized.
>

value initialization in c++ fills zero to the first value in union.
If the second or later values in the union is large than the first
value, they are not zero-filled.
So I would use memset for a structure with a union.

> >
> >       unsigned int i = 0;
>
> Should we replace i with
>
>         v4l2_ext_control *v4l2Ctrl = v4l2Ctrls.data();
>
> and do a
>
>         v4l2Ctrl++;
>
> at the end of the loop ? That way we would ensure that i won't be used
> incorrectly (after being incremented) inside the loop.
>
> Apart from that,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> >       for (auto &ctrl : *ctrls) {
> > @@ -295,14 +294,14 @@ int V4L2Device::setControls(ControlList *ctrls)
> >                               << "Control " << utils::hex(id) << " not found";
> >                       return -EINVAL;
> >               }
> > -
> > -             v4l2Ctrls[i].id = id;
> > +             v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
> > +             v4l2Ctrl.id = id;
> >
> >               /* Set the v4l2_ext_control value for the write operation. */
> >               ControlValue &value = ctrl.second;
> >               switch (iter->first->type()) {
> >               case ControlTypeInteger64:
> > -                     v4l2Ctrls[i].value64 = value.get<int64_t>();
> > +                     v4l2Ctrl.value64 = value.get<int64_t>();
> >                       break;
> >
> >               case ControlTypeByte: {
> > @@ -314,32 +313,30 @@ int V4L2Device::setControls(ControlList *ctrls)
> >                       }
> >
> >                       Span<uint8_t> data = value.data();
> > -                     v4l2Ctrls[i].p_u8 = data.data();
> > -                     v4l2Ctrls[i].size = data.size();
> > +                     v4l2Ctrl.p_u8 = data.data();
> > +                     v4l2Ctrl.size = data.size();
> >
> >                       break;
> >               }
> >
> >               default:
> >                       /* \todo To be changed to support strings. */
> > -                     v4l2Ctrls[i].value = value.get<int32_t>();
> > +                     v4l2Ctrl.value = value.get<int32_t>();
> >                       break;
> >               }
> > -
> > -             i++;
> >       }
> >
> >       struct v4l2_ext_controls v4l2ExtCtrls = {};
> >       v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
> > -     v4l2ExtCtrls.controls = v4l2Ctrls;
> > -     v4l2ExtCtrls.count = count;
> > +     v4l2ExtCtrls.controls = v4l2Ctrls.data();
> > +     v4l2ExtCtrls.count = v4l2Ctrls.size();
> >
> >       int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
> >       if (ret) {
> >               unsigned int errorIdx = v4l2ExtCtrls.error_idx;
> >
> >               /* Generic validation error. */
> > -             if (errorIdx == 0 || errorIdx >= count) {
> > +             if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
> >                       LOG(V4L2, Error) << "Unable to set controls: "
> >                                        << strerror(-ret);
> >                       return -EINVAL;
> > @@ -348,11 +345,12 @@ int V4L2Device::setControls(ControlList *ctrls)
> >               /* A specific control failed. */
> >               LOG(V4L2, Error) << "Unable to set control " << errorIdx
> >                                << ": " << strerror(-ret);
> > -             count = errorIdx - 1;
> > +
> > +             v4l2Ctrls.resize(errorIdx);
> >               ret = errorIdx;
> >       }
> >
> > -     updateControls(ctrls, v4l2Ctrls, count);
> > +     updateControls(ctrls, v4l2Ctrls.data(), v4l2Ctrls.size());
> >
> >       return ret;
> >  }
>
> --
> Regards,
>
> Laurent Pinchart
Laurent Pinchart April 21, 2021, 9:34 a.m. UTC | #3 
Hi Hiro,

On Wed, Apr 21, 2021 at 06:30:50PM +0900, Hirokazu Honda wrote:
> On Tue, Apr 20, 2021 at 10:15 AM Laurent Pinchart wrote:
> > On Thu, Apr 15, 2021 at 01:48:53PM +0900, Hirokazu Honda wrote:
> > > The original code uses Variable-Length-Array, which is not
> > > officially supported in C++. This replaces the array with
> > > std::vector.
> > >
> > > Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
> > > Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> > > ---
> > >  src/libcamera/v4l2_device.cpp | 32 +++++++++++++++-----------------
> > >  1 file changed, 15 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > > index ee8c3fed..5ec1b10e 100644
> > > --- a/src/libcamera/v4l2_device.cpp
> > > +++ b/src/libcamera/v4l2_device.cpp
> > > @@ -279,12 +279,11 @@ ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
> > >   */
> > >  int V4L2Device::setControls(ControlList *ctrls)
> > >  {
> > > -     unsigned int count = ctrls->size();
> > > -     if (count == 0)
> > > +     if (ctrls->empty())
> > >               return 0;
> > >
> > > -     struct v4l2_ext_control v4l2Ctrls[count];
> > > -     memset(v4l2Ctrls, 0, sizeof(v4l2Ctrls));
> > > +     std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size());
> > > +     memset(v4l2Ctrls.data(), 0, v4l2Ctrls.size());
> >
> > Is the memset() needed ? The std::vector constructor will default-insert
> > the elements, which value-initializes them. If my interpretation of
> > https://en.cppreference.com/w/cpp/language/value_initialization is
> > correct, the elements will be zero-initialized.
> 
> value initialization in c++ fills zero to the first value in union.
> If the second or later values in the union is large than the first
> value, they are not zero-filled.
> So I would use memset for a structure with a union.

Good point, let's keep the memset() then.

> > >
> > >       unsigned int i = 0;
> >
> > Should we replace i with
> >
> >         v4l2_ext_control *v4l2Ctrl = v4l2Ctrls.data();
> >
> > and do a
> >
> >         v4l2Ctrl++;
> >
> > at the end of the loop ? That way we would ensure that i won't be used
> > incorrectly (after being incremented) inside the loop.
> >
> > Apart from that,
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > >       for (auto &ctrl : *ctrls) {
> > > @@ -295,14 +294,14 @@ int V4L2Device::setControls(ControlList *ctrls)
> > >                               << "Control " << utils::hex(id) << " not found";
> > >                       return -EINVAL;
> > >               }
> > > -
> > > -             v4l2Ctrls[i].id = id;
> > > +             v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
> > > +             v4l2Ctrl.id = id;
> > >
> > >               /* Set the v4l2_ext_control value for the write operation. */
> > >               ControlValue &value = ctrl.second;
> > >               switch (iter->first->type()) {
> > >               case ControlTypeInteger64:
> > > -                     v4l2Ctrls[i].value64 = value.get<int64_t>();
> > > +                     v4l2Ctrl.value64 = value.get<int64_t>();
> > >                       break;
> > >
> > >               case ControlTypeByte: {
> > > @@ -314,32 +313,30 @@ int V4L2Device::setControls(ControlList *ctrls)
> > >                       }
> > >
> > >                       Span<uint8_t> data = value.data();
> > > -                     v4l2Ctrls[i].p_u8 = data.data();
> > > -                     v4l2Ctrls[i].size = data.size();
> > > +                     v4l2Ctrl.p_u8 = data.data();
> > > +                     v4l2Ctrl.size = data.size();
> > >
> > >                       break;
> > >               }
> > >
> > >               default:
> > >                       /* \todo To be changed to support strings. */
> > > -                     v4l2Ctrls[i].value = value.get<int32_t>();
> > > +                     v4l2Ctrl.value = value.get<int32_t>();
> > >                       break;
> > >               }
> > > -
> > > -             i++;
> > >       }
> > >
> > >       struct v4l2_ext_controls v4l2ExtCtrls = {};
> > >       v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
> > > -     v4l2ExtCtrls.controls = v4l2Ctrls;
> > > -     v4l2ExtCtrls.count = count;
> > > +     v4l2ExtCtrls.controls = v4l2Ctrls.data();
> > > +     v4l2ExtCtrls.count = v4l2Ctrls.size();
> > >
> > >       int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
> > >       if (ret) {
> > >               unsigned int errorIdx = v4l2ExtCtrls.error_idx;
> > >
> > >               /* Generic validation error. */
> > > -             if (errorIdx == 0 || errorIdx >= count) {
> > > +             if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
> > >                       LOG(V4L2, Error) << "Unable to set controls: "
> > >                                        << strerror(-ret);
> > >                       return -EINVAL;
> > > @@ -348,11 +345,12 @@ int V4L2Device::setControls(ControlList *ctrls)
> > >               /* A specific control failed. */
> > >               LOG(V4L2, Error) << "Unable to set control " << errorIdx
> > >                                << ": " << strerror(-ret);
> > > -             count = errorIdx - 1;
> > > +
> > > +             v4l2Ctrls.resize(errorIdx);
> > >               ret = errorIdx;
> > >       }
> > >
> > > -     updateControls(ctrls, v4l2Ctrls, count);
> > > +     updateControls(ctrls, v4l2Ctrls.data(), v4l2Ctrls.size());
> > >
> > >       return ret;
> > >  }

Patch
diff mbox series 

diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index ee8c3fed..5ec1b10e 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -279,12 +279,11 @@  ControlList V4L2Device::getControls(const std::vector<uint32_t> &ids)
  */
 int V4L2Device::setControls(ControlList *ctrls)
 {
-	unsigned int count = ctrls->size();
-	if (count == 0)
+	if (ctrls->empty())
 		return 0;
 
-	struct v4l2_ext_control v4l2Ctrls[count];
-	memset(v4l2Ctrls, 0, sizeof(v4l2Ctrls));
+	std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size());
+	memset(v4l2Ctrls.data(), 0, v4l2Ctrls.size());
 
 	unsigned int i = 0;
 	for (auto &ctrl : *ctrls) {
@@ -295,14 +294,14 @@  int V4L2Device::setControls(ControlList *ctrls)
 				<< "Control " << utils::hex(id) << " not found";
 			return -EINVAL;
 		}
-
-		v4l2Ctrls[i].id = id;
+		v4l2_ext_control &v4l2Ctrl = v4l2Ctrls[i++];
+		v4l2Ctrl.id = id;
 
 		/* Set the v4l2_ext_control value for the write operation. */
 		ControlValue &value = ctrl.second;
 		switch (iter->first->type()) {
 		case ControlTypeInteger64:
-			v4l2Ctrls[i].value64 = value.get<int64_t>();
+			v4l2Ctrl.value64 = value.get<int64_t>();
 			break;
 
 		case ControlTypeByte: {
@@ -314,32 +313,30 @@  int V4L2Device::setControls(ControlList *ctrls)
 			}
 
 			Span<uint8_t> data = value.data();
-			v4l2Ctrls[i].p_u8 = data.data();
-			v4l2Ctrls[i].size = data.size();
+			v4l2Ctrl.p_u8 = data.data();
+			v4l2Ctrl.size = data.size();
 
 			break;
 		}
 
 		default:
 			/* \todo To be changed to support strings. */
-			v4l2Ctrls[i].value = value.get<int32_t>();
+			v4l2Ctrl.value = value.get<int32_t>();
 			break;
 		}
-
-		i++;
 	}
 
 	struct v4l2_ext_controls v4l2ExtCtrls = {};
 	v4l2ExtCtrls.which = V4L2_CTRL_WHICH_CUR_VAL;
-	v4l2ExtCtrls.controls = v4l2Ctrls;
-	v4l2ExtCtrls.count = count;
+	v4l2ExtCtrls.controls = v4l2Ctrls.data();
+	v4l2ExtCtrls.count = v4l2Ctrls.size();
 
 	int ret = ioctl(VIDIOC_S_EXT_CTRLS, &v4l2ExtCtrls);
 	if (ret) {
 		unsigned int errorIdx = v4l2ExtCtrls.error_idx;
 
 		/* Generic validation error. */
-		if (errorIdx == 0 || errorIdx >= count) {
+		if (errorIdx == 0 || errorIdx >= v4l2Ctrls.size()) {
 			LOG(V4L2, Error) << "Unable to set controls: "
 					 << strerror(-ret);
 			return -EINVAL;
@@ -348,11 +345,12 @@  int V4L2Device::setControls(ControlList *ctrls)
 		/* A specific control failed. */
 		LOG(V4L2, Error) << "Unable to set control " << errorIdx
 				 << ": " << strerror(-ret);
-		count = errorIdx - 1;
+
+		v4l2Ctrls.resize(errorIdx);
 		ret = errorIdx;
 	}
 
-	updateControls(ctrls, v4l2Ctrls, count);
+	updateControls(ctrls, v4l2Ctrls.data(), v4l2Ctrls.size());
 
 	return ret;
 }