libcamera: matrix: Add read-only accessor to internal data

Add a data() function to the Matrix class to access the internal data.
This is useful for code that needs to use the matrix contents as a
linear array, as shown by the RkISP1::Ccm::process() function that needs
to copy the matrix data to a local variable. Simplify that function by
using the new accessor.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>

include/libcamera/internal/matrix.h

@@ -66,6 +66,8 @@ public:
 		return out.str();
 	}
 
+	Span<const T, Rows * Cols> data() const { return data_; }
+
 	Span<const T, Cols> operator[](size_t i) const
 	{
 		return Span<const T, Cols>{ &data_.data()[i * Cols], Cols };