media: xilinx: Avoid -Wflex-array-member-not-at-end warning

[PATCH][next] media: xilinx: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 1 month, 2 weeks ago

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the TRAILING_OVERLAP() helper to fix the following warning:

drivers/media/platform/xilinx/xilinx-dma.h:99:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM)
and a set of members that would otherwise follow it. This overlays
the trailing members onto the FAM while preserving the original
memory layout.

Lastly, the static_assert() ensures the alignment between the FAM
and struct data_chunk sgl; is not inadvertently changed, and it's
intentionally placed inmediately after the related structure (that
is, no blank line in between).

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/media/platform/xilinx/xilinx-dma.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/xilinx/xilinx-dma.h b/drivers/media/platform/xilinx/xilinx-dma.h
index 18f77e1a7b39..65f6147ff6c6 100644
--- a/drivers/media/platform/xilinx/xilinx-dma.h
+++ b/drivers/media/platform/xilinx/xilinx-dma.h
@@ -96,9 +96,14 @@ struct xvip_dma {
 
 	struct dma_chan *dma;
 	unsigned int align;
-	struct dma_interleaved_template xt;
-	struct data_chunk sgl;
+
+	/* Must be last as it ends in a flexible-array member. */
+	TRAILING_OVERLAP(struct dma_interleaved_template, xt, sgl,
+		struct data_chunk sgl;
+	);
 };
+static_assert(offsetof(struct xvip_dma, xt.sgl) ==
+	      offsetof(struct xvip_dma, sgl));
 
 #define to_xvip_dma(vdev)	container_of(vdev, struct xvip_dma, video)
 
-- 
2.51.0

Re: [PATCH][next] media: xilinx: Avoid -Wflex-array-member-not-at-end warning

Posted by Laurent Pinchart 1 month, 2 weeks ago

CC'ing Tomi Valkeinen.

On a side note, Tomi, can I send a patch to add you to the "XILINX VIDEO
IP CORES" section of MAINTAINERS ?

On Wed, Apr 29, 2026 at 01:55:27PM -0600, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the TRAILING_OVERLAP() helper to fix the following warning:
> 
> drivers/media/platform/xilinx/xilinx-dma.h:99:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM)
> and a set of members that would otherwise follow it. This overlays
> the trailing members onto the FAM while preserving the original
> memory layout.
> 
> Lastly, the static_assert() ensures the alignment between the FAM
> and struct data_chunk sgl; is not inadvertently changed, and it's
> intentionally placed inmediately after the related structure (that
> is, no blank line in between).
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

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

> ---
>  drivers/media/platform/xilinx/xilinx-dma.h | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/xilinx/xilinx-dma.h b/drivers/media/platform/xilinx/xilinx-dma.h
> index 18f77e1a7b39..65f6147ff6c6 100644
> --- a/drivers/media/platform/xilinx/xilinx-dma.h
> +++ b/drivers/media/platform/xilinx/xilinx-dma.h
> @@ -96,9 +96,14 @@ struct xvip_dma {
>  
>  	struct dma_chan *dma;
>  	unsigned int align;
> -	struct dma_interleaved_template xt;
> -	struct data_chunk sgl;
> +
> +	/* Must be last as it ends in a flexible-array member. */
> +	TRAILING_OVERLAP(struct dma_interleaved_template, xt, sgl,
> +		struct data_chunk sgl;
> +	);
>  };
> +static_assert(offsetof(struct xvip_dma, xt.sgl) ==
> +	      offsetof(struct xvip_dma, sgl));
>  
>  #define to_xvip_dma(vdev)	container_of(vdev, struct xvip_dma, video)
>  

-- 
Regards,

Laurent Pinchart

Re: [PATCH][next] media: xilinx: Avoid -Wflex-array-member-not-at-end warning

Posted by Laurent Pinchart 1 month, 2 weeks ago

I forgot to ask, how do you want to get this merged? Will you collect
all similar patches and send a tree-wide pull request, or should they be
merged by individual subsystems ? In the latter case, Tomi, could you
please handle this with other Xilinx patches ?

On Wed, Apr 29, 2026 at 11:24:50PM +0300, Laurent Pinchart wrote:
> CC'ing Tomi Valkeinen.
> 
> On a side note, Tomi, can I send a patch to add you to the "XILINX VIDEO
> IP CORES" section of MAINTAINERS ?
> 
> On Wed, Apr 29, 2026 at 01:55:27PM -0600, Gustavo A. R. Silva wrote:
> > -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> > getting ready to enable it, globally.
> > 
> > Use the TRAILING_OVERLAP() helper to fix the following warning:
> > 
> > drivers/media/platform/xilinx/xilinx-dma.h:99:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> > 
> > This helper creates a union between a flexible-array member (FAM)
> > and a set of members that would otherwise follow it. This overlays
> > the trailing members onto the FAM while preserving the original
> > memory layout.
> > 
> > Lastly, the static_assert() ensures the alignment between the FAM
> > and struct data_chunk sgl; is not inadvertently changed, and it's
> > intentionally placed inmediately after the related structure (that
> > is, no blank line in between).
> > 
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> > ---
> >  drivers/media/platform/xilinx/xilinx-dma.h | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/media/platform/xilinx/xilinx-dma.h b/drivers/media/platform/xilinx/xilinx-dma.h
> > index 18f77e1a7b39..65f6147ff6c6 100644
> > --- a/drivers/media/platform/xilinx/xilinx-dma.h
> > +++ b/drivers/media/platform/xilinx/xilinx-dma.h
> > @@ -96,9 +96,14 @@ struct xvip_dma {
> >  
> >  	struct dma_chan *dma;
> >  	unsigned int align;
> > -	struct dma_interleaved_template xt;
> > -	struct data_chunk sgl;
> > +
> > +	/* Must be last as it ends in a flexible-array member. */
> > +	TRAILING_OVERLAP(struct dma_interleaved_template, xt, sgl,
> > +		struct data_chunk sgl;
> > +	);
> >  };
> > +static_assert(offsetof(struct xvip_dma, xt.sgl) ==
> > +	      offsetof(struct xvip_dma, sgl));
> >  
> >  #define to_xvip_dma(vdev)	container_of(vdev, struct xvip_dma, video)
> >  

-- 
Regards,

Laurent Pinchart

Re: [PATCH][next] media: xilinx: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 1 month, 2 weeks ago


On 4/29/26 14:28, Laurent Pinchart wrote:
> I forgot to ask, how do you want to get this merged? Will you collect
> all similar patches and send a tree-wide pull request, or should they be
> merged by individual subsystems ? In the latter case, Tomi, could you
> please handle this with other Xilinx patches ?

You folks can take this in your tree. :)

Thanks!
-Gustavo

> 
> On Wed, Apr 29, 2026 at 11:24:50PM +0300, Laurent Pinchart wrote:
>> CC'ing Tomi Valkeinen.
>>
>> On a side note, Tomi, can I send a patch to add you to the "XILINX VIDEO
>> IP CORES" section of MAINTAINERS ?
>>
>> On Wed, Apr 29, 2026 at 01:55:27PM -0600, Gustavo A. R. Silva wrote:
>>> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
>>> getting ready to enable it, globally.
>>>
>>> Use the TRAILING_OVERLAP() helper to fix the following warning:
>>>
>>> drivers/media/platform/xilinx/xilinx-dma.h:99:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>>>
>>> This helper creates a union between a flexible-array member (FAM)
>>> and a set of members that would otherwise follow it. This overlays
>>> the trailing members onto the FAM while preserving the original
>>> memory layout.
>>>
>>> Lastly, the static_assert() ensures the alignment between the FAM
>>> and struct data_chunk sgl; is not inadvertently changed, and it's
>>> intentionally placed inmediately after the related structure (that
>>> is, no blank line in between).
>>>
>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>>
>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>>
>>> ---
>>>   drivers/media/platform/xilinx/xilinx-dma.h | 9 +++++++--
>>>   1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/xilinx/xilinx-dma.h b/drivers/media/platform/xilinx/xilinx-dma.h
>>> index 18f77e1a7b39..65f6147ff6c6 100644
>>> --- a/drivers/media/platform/xilinx/xilinx-dma.h
>>> +++ b/drivers/media/platform/xilinx/xilinx-dma.h
>>> @@ -96,9 +96,14 @@ struct xvip_dma {
>>>   
>>>   	struct dma_chan *dma;
>>>   	unsigned int align;
>>> -	struct dma_interleaved_template xt;
>>> -	struct data_chunk sgl;
>>> +
>>> +	/* Must be last as it ends in a flexible-array member. */
>>> +	TRAILING_OVERLAP(struct dma_interleaved_template, xt, sgl,
>>> +		struct data_chunk sgl;
>>> +	);
>>>   };
>>> +static_assert(offsetof(struct xvip_dma, xt.sgl) ==
>>> +	      offsetof(struct xvip_dma, sgl));
>>>   
>>>   #define to_xvip_dma(vdev)	container_of(vdev, struct xvip_dma, video)
>>>   
>