[libcamera-devel,2/3] libcamera: V4L2Device: Use std::vector for v4l2_ext_control in setControls()
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Message ID 20210413061925.3054927-2-hiroh@chromium.org
State Superseded
Headers show
Series
  • [libcamera-devel,1/3] libcamera: V4L2Device: Use std::vector for v4l2_ext_control in getControls()
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Commit Message

Hirokazu Honda April 13, 2021, 6:19 a.m. UTC 
The original code uses Variable-Length-Array, which is not
officially supported in C++. This replaces the array with
std::vector.
---
 src/libcamera/v4l2_device.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

Comments

Kieran Bingham April 13, 2021, 10:14 p.m. UTC | #1 
Hi Hiro,

On 13/04/2021 07:19, Hirokazu Honda wrote:
> The original code uses Variable-Length-Array, which is not
> officially supported in C++. This replaces the array with
> std::vector.
> ---
>  src/libcamera/v4l2_device.cpp | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> index 78c289c2..8625dde8 100644
> --- a/src/libcamera/v4l2_device.cpp
> +++ b/src/libcamera/v4l2_device.cpp
> @@ -280,12 +280,11 @@ 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());

Does the vector not initialise in anyway ?

Looking at https://www.cplusplus.com/reference/vector/vector/vector/
this must be using the fill(2) constructor.

I suspect if nothing is provided, it won't fill, so perhaps it's not
initialised, but if that's the case, I wonder if the right way to
construct this is more like:

	std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size(), {});

But I'm not particular certain.

Otherwise, this looks Ok to me...

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

>  
>  	unsigned int i = 0;
>  	for (auto &ctrl : *ctrls) {
> @@ -332,15 +331,15 @@ int V4L2Device::setControls(ControlList *ctrls)
>  
>  	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;
> @@ -349,11 +348,12 @@ 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 15, 2021, 3:58 a.m. UTC | #2 
On Wed, Apr 14, 2021 at 7:14 AM Kieran Bingham
<kieran.bingham@ideasonboard.com> wrote:
>
> Hi Hiro,
>
> On 13/04/2021 07:19, Hirokazu Honda wrote:
> > The original code uses Variable-Length-Array, which is not
> > officially supported in C++. This replaces the array with
> > std::vector.
> > ---
> >  src/libcamera/v4l2_device.cpp | 18 +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
> > index 78c289c2..8625dde8 100644
> > --- a/src/libcamera/v4l2_device.cpp
> > +++ b/src/libcamera/v4l2_device.cpp
> > @@ -280,12 +280,11 @@ 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());
>
> Does the vector not initialise in anyway ?
>
> Looking at https://www.cplusplus.com/reference/vector/vector/vector/
> this must be using the fill(2) constructor.
>
> I suspect if nothing is provided, it won't fill, so perhaps it's not
> initialised, but if that's the case, I wonder if the right way to
> construct this is more like:
>
>         std::vector<v4l2_ext_control> v4l2Ctrls(ctrls->size(), {});

As replied to 1/3, I don't trust the zero initialization by {}.
So I would rather use std::memset.

Best Regards,
-Hiro
>
> But I'm not particular certain.
>
> Otherwise, this looks Ok to me...
>
> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
>
> >
> >       unsigned int i = 0;
> >       for (auto &ctrl : *ctrls) {
> > @@ -332,15 +331,15 @@ int V4L2Device::setControls(ControlList *ctrls)
> >
> >       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;
> > @@ -349,11 +348,12 @@ 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
> --
> Kieran

Patch
diff mbox series 

diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 78c289c2..8625dde8 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -280,12 +280,11 @@  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) {
@@ -332,15 +331,15 @@  int V4L2Device::setControls(ControlList *ctrls)
 
 	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;
@@ -349,11 +348,12 @@  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;
 }