[libcamera-devel] [PATCH v2 3/4] libcamera: controls: Construct Span with size for array controls

[Umang Jain]

Hi Laurent,

On 10/7/22 4:37 AM, Laurent Pinchart via libcamera-devel wrote:
> The ControlList::set() function overload used for array controls
> constructs a Span from an initializer list. It doesn't specify the Span
> size explicitly, which results in a dynamic extent Span being
> constructed. That causes a compilation failure for fixed-size array
> controls, as they are defined as Control<T> with T being a fixed-extent
> Span, and conversion from a dynamic-extent to fixed-extent Span when
> calling ControlValue::set() can't be implicit.
>
> Fix this by constructing the Span using the size of the control, which
> resolves to a fixed-extent and dynamic-extent Span for fixed-size and
> dynamic-size array controls respectively. The ControlList::set()
> function that takes an initializer list can then be used for fixed-size
> array controls.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>

> ---
>   include/libcamera/controls.h | 6 +++---
>   src/libcamera/controls.cpp   | 2 +-
>   2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/libcamera/controls.h b/include/libcamera/controls.h
> index 38d0a3e8360a..cf94205577a5 100644
> --- a/include/libcamera/controls.h
> +++ b/include/libcamera/controls.h
> @@ -393,14 +393,14 @@ public:
>   		val->set<T>(value);
>   	}
>   
> -	template<typename T, typename V>
> -	void set(const Control<T> &ctrl, const std::initializer_list<V> &value)
> +	template<typename T, typename V, size_t Size>
> +	void set(const Control<Span<T, Size>> &ctrl, const std::initializer_list<V> &value)
>   	{
>   		ControlValue *val = find(ctrl.id());
>   		if (!val)
>   			return;
>   
> -		val->set<T>(Span<const typename std::remove_cv_t<V>>{ value.begin(), value.size() });
> +		val->set(Span<const typename std::remove_cv_t<V>, Size>{ value.begin(), value.size() });
>   	}
>   
>   	const ControlValue &get(unsigned int id) const;
> diff --git a/src/libcamera/controls.cpp b/src/libcamera/controls.cpp
> index bc3db4f69388..6dbf9b348709 100644
> --- a/src/libcamera/controls.cpp
> +++ b/src/libcamera/controls.cpp
> @@ -970,7 +970,7 @@ bool ControlList::contains(unsigned int id) const
>    */
>   
>   /**
> - * \fn ControlList::set(const Control<T> &ctrl, const std::initializer_list<V> &value)
> + * \fn ControlList::set(const Control<Span<T, Size>> &ctrl, const std::initializer_list<V> &value)
>    * \copydoc ControlList::set(const Control<T> &ctrl, const V &value)
>    */
>