As we get ready for kzalloc checking for invalid sizes, let's add
documentation for the cases where the size is different but valid.

This patch fixes this cocci warning:
./platform/qcom/iris/iris_hfi_gen2_command.c:1215:9-25: WARNING: casting value returned by memory allocation function to (struct iris_inst *) is useless.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
index f9129553209922fda548ca320494ae6ae797854c..ab91afd0597045bd876d0411b08b5a3421b12c70 100644
--- a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
+++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
@@ -1212,5 +1212,13 @@ void iris_hfi_gen2_command_ops_init(struct iris_core *core)
 
 struct iris_inst *iris_hfi_gen2_get_instance(void)
 {
-	return (struct iris_inst *)kzalloc(sizeof(struct iris_inst_hfi_gen2), GFP_KERNEL);
+	struct iris_inst_hfi_gen2 *out;
+
+	/*
+	 * The allocation is intentionally larger. The first member of
+	 * struct iris_hfi_gen2 is struct iris_inst.
+	 */
+	out = kzalloc(sizeof(*out), GFP_KERNEL);
+
+	return (struct iris_inst *)out;
 }

-- 
2.52.0.158.g65b55ccf14-goog

On Wed, Dec 03, 2025 at 08:55:35AM +0000, Ricardo Ribalda wrote:
> As we get ready for kzalloc checking for invalid sizes, let's add
> documentation for the cases where the size is different but valid.
> 
> This patch fixes this cocci warning:
> ./platform/qcom/iris/iris_hfi_gen2_command.c:1215:9-25: WARNING: casting value returned by memory allocation function to (struct iris_inst *) is useless.
> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> index f9129553209922fda548ca320494ae6ae797854c..ab91afd0597045bd876d0411b08b5a3421b12c70 100644
> --- a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> +++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> @@ -1212,5 +1212,13 @@ void iris_hfi_gen2_command_ops_init(struct iris_core *core)
>  
>  struct iris_inst *iris_hfi_gen2_get_instance(void)
>  {
> -	return (struct iris_inst *)kzalloc(sizeof(struct iris_inst_hfi_gen2), GFP_KERNEL);
> +	struct iris_inst_hfi_gen2 *out;
> +
> +	/*
> +	 * The allocation is intentionally larger. The first member of
> +	 * struct iris_hfi_gen2 is struct iris_inst.
> +	 */
> +	out = kzalloc(sizeof(*out), GFP_KERNEL);
> +
> +	return (struct iris_inst *)out;

	return &out->inst;

would be more readable. You can then drop the comment.

>  }
> 

-- 
Regards,

Laurent Pinchart

Hi Laurent



On Wed, 3 Dec 2025 at 10:17, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Wed, Dec 03, 2025 at 08:55:35AM +0000, Ricardo Ribalda wrote:
> > As we get ready for kzalloc checking for invalid sizes, let's add
> > documentation for the cases where the size is different but valid.
> >
> > This patch fixes this cocci warning:
> > ./platform/qcom/iris/iris_hfi_gen2_command.c:1215:9-25: WARNING: casting value returned by memory allocation function to (struct iris_inst *) is useless.
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c | 10 +++++++++-
> >  1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> > index f9129553209922fda548ca320494ae6ae797854c..ab91afd0597045bd876d0411b08b5a3421b12c70 100644
> > --- a/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> > +++ b/drivers/media/platform/qcom/iris/iris_hfi_gen2_command.c
> > @@ -1212,5 +1212,13 @@ void iris_hfi_gen2_command_ops_init(struct iris_core *core)
> >
> >  struct iris_inst *iris_hfi_gen2_get_instance(void)
> >  {
> > -     return (struct iris_inst *)kzalloc(sizeof(struct iris_inst_hfi_gen2), GFP_KERNEL);
> > +     struct iris_inst_hfi_gen2 *out;
> > +
> > +     /*
> > +      * The allocation is intentionally larger. The first member of
> > +      * struct iris_hfi_gen2 is struct iris_inst.
> > +      */
> > +     out = kzalloc(sizeof(*out), GFP_KERNEL);
> > +
> > +     return (struct iris_inst *)out;
>
>         return &out->inst;
>
> would be more readable. You can then drop the comment.

It looks better, and it is more robust. Thanks

I prefer to leave a small comment though:

+       struct iris_inst_hfi_gen2 *out;
+
+       /* The allocation is intentionally larger than struct iris_inst. */
+       out = kzalloc(sizeof(*out), GFP_KERNEL);
+
+       return &out->inst;


Regards

>
> >  }
> >
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda