[PATCH v2][next] drm/nouveau: disp: Avoid -Wflex-array-member-not-at-end warning

[PATCH v2][next] drm/nouveau: disp: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

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

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:

drivers/gpu/drm/nouveau/dispnv50/disp.c:779:47: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v2:
 - Calculate the size of `data[]` using ` __struct_size(args) - sizeof(*args)`.

v1:
 - Link: https://lore.kernel.org/linux-hardening/ZsZLFS1CsHkKjw+C@elsanto/

 drivers/gpu/drm/nouveau/dispnv50/disp.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 504cb3f2054b..725331638a15 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -775,10 +775,8 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
 	union hdmi_infoframe infoframe = { 0 };
 	const u8 rekey = 56; /* binary driver, and tegra, constant */
 	u32 max_ac_packet;
-	struct {
-		struct nvif_outp_infoframe_v0 infoframe;
-		u8 data[17];
-	} args = { 0 };
+	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
+	const u8 data_len = __struct_size(args) - sizeof(*args);
 	int ret, size;
 
 	max_ac_packet  = mode->htotal - mode->hdisplay;
@@ -815,29 +813,29 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
 		return;
 
 	/* AVI InfoFrame. */
-	args.infoframe.version = 0;
-	args.infoframe.head = nv_crtc->index;
+	args->version = 0;
+	args->head = nv_crtc->index;
 
 	if (!drm_hdmi_avi_infoframe_from_display_mode(&infoframe.avi, &nv_connector->base, mode)) {
 		drm_hdmi_avi_infoframe_quant_range(&infoframe.avi, &nv_connector->base, mode,
 						   HDMI_QUANTIZATION_RANGE_FULL);
 
-		size = hdmi_infoframe_pack(&infoframe, args.data, ARRAY_SIZE(args.data));
+		size = hdmi_infoframe_pack(&infoframe, args->data, data_len);
 	} else {
 		size = 0;
 	}
 
-	nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_AVI, &args.infoframe, size);
+	nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_AVI, args, size);
 
 	/* Vendor InfoFrame. */
-	memset(&args.data, 0, sizeof(args.data));
+	memset(args->data, 0, data_len);
 	if (!drm_hdmi_vendor_infoframe_from_display_mode(&infoframe.vendor.hdmi,
 							 &nv_connector->base, mode))
-		size = hdmi_infoframe_pack(&infoframe, args.data, ARRAY_SIZE(args.data));
+		size = hdmi_infoframe_pack(&infoframe, args->data, data_len);
 	else
 		size = 0;
 
-	nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_VSI, &args.infoframe, size);
+	nvif_outp_infoframe(&nv_encoder->outp, NVIF_OUTP_INFOFRAME_V0_VSI, args, size);
 
 	nv_encoder->hdmi.enabled = true;
 }
-- 
2.43.0

Re: [PATCH v2][next] drm/nouveau: disp: Avoid -Wflex-array-member-not-at-end warning

[Danilo Krummrich]

On Wed, Apr 02, 2025 at 03:58:59PM -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 `DEFINE_RAW_FLEX()` helper for an on-stack definition of
> a flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> 
> drivers/gpu/drm/nouveau/dispnv50/disp.c:779:47: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Applied this one (as well as the svm and fence one) to drm-misc-next, thanks!

Re: [PATCH v2][next] drm/nouveau: disp: Avoid -Wflex-array-member-not-at-end warning

[Gustavo A. R. Silva]

> Applied this one (as well as the svm and fence one) to drm-misc-next, thanks!

Awesome. :)

Thanks!
--
Gustavo