drm/nouveau: Avoid -Wflex-array-member-not-at-end warning

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

Posted by Gustavo A. R. Silva 1 year, 5 months ago

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 this, 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>
---
 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 eed579a6c858..ddddc69640be 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
 	struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
 	union hdmi_infoframe infoframe = { 0 };
 	const u8 rekey = 56; /* binary driver, and tegra, constant */
+	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
+	const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
 	u32 max_ac_packet;
-	struct {
-		struct nvif_outp_infoframe_v0 infoframe;
-		u8 data[17];
-	} args = { 0 };
 	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;
 }
-- 
2.34.1

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

Posted by Gustavo A. R. Silva 1 year, 4 months ago

Hi all,

Friendly ping: who can take this, please? 🙂

Thanks
-Gustavo

On 21/08/24 22:16, Gustavo A. R. Silva wrote:
> 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 this, 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>
> ---
>   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 eed579a6c858..ddddc69640be 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
>   	struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>   	union hdmi_infoframe infoframe = { 0 };
>   	const u8 rekey = 56; /* binary driver, and tegra, constant */
> +	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
> +	const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
>   	u32 max_ac_packet;
> -	struct {
> -		struct nvif_outp_infoframe_v0 infoframe;
> -		u8 data[17];
> -	} args = { 0 };
>   	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;
>   }

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

Posted by Danilo Krummrich 1 year, 4 months ago

Hi,

On 9/13/24 10:09 AM, Gustavo A. R. Silva wrote:
> Hi all,
> 
> Friendly ping: who can take this, please? 🙂

Usually, that's me. But I thought you might want to send a v2 based on Kees'
comments?

- Danilo

> 
> Thanks
> -Gustavo
> 
> On 21/08/24 22:16, Gustavo A. R. Silva wrote:
>> 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 this, 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>
>> ---
>>   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 eed579a6c858..ddddc69640be 100644
>> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct 
>> nouveau_crtc *nv_crtc,
>>       struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>>       union hdmi_infoframe infoframe = { 0 };
>>       const u8 rekey = 56; /* binary driver, and tegra, constant */
>> +    DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
>> +    const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
>>       u32 max_ac_packet;
>> -    struct {
>> -        struct nvif_outp_infoframe_v0 infoframe;
>> -        u8 data[17];
>> -    } args = { 0 };
>>       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;
>>   }
>

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

Posted by Danilo Krummrich 1 year, 4 months ago

On 9/13/24 12:23 PM, Danilo Krummrich wrote:
> Hi,
> 
> On 9/13/24 10:09 AM, Gustavo A. R. Silva wrote:
>> Hi all,
>>
>> Friendly ping: who can take this, please? 🙂
> 
> Usually, that's me. But I thought you might want to send a v2 based on Kees'
> comments?

Do you plan to follow up on this? I'd prefer if we could get rid of the open-
coded "17". So, maybe just go with the define until we have something like
STACK_FLEX_COUNT()?

> 
> - Danilo
> 
>>
>> Thanks
>> -Gustavo
>>
>> On 21/08/24 22:16, Gustavo A. R. Silva wrote:
>>> 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 this, 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>
>>> ---
>>>   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 eed579a6c858..ddddc69640be 100644
>>> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
>>> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
>>> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct 
>>> nouveau_crtc *nv_crtc,
>>>       struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>>>       union hdmi_infoframe infoframe = { 0 };
>>>       const u8 rekey = 56; /* binary driver, and tegra, constant */
>>> +    DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
>>> +    const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
>>>       u32 max_ac_packet;
>>> -    struct {
>>> -        struct nvif_outp_infoframe_v0 infoframe;
>>> -        u8 data[17];
>>> -    } args = { 0 };
>>>       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;
>>>   }
>>

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

Posted by Gustavo A. R. Silva 1 year, 4 months ago


On 03/10/24 12:36, Danilo Krummrich wrote:
> On 9/13/24 12:23 PM, Danilo Krummrich wrote:
>> Hi,
>>
>> On 9/13/24 10:09 AM, Gustavo A. R. Silva wrote:
>>> Hi all,
>>>
>>> Friendly ping: who can take this, please? 🙂
>>
>> Usually, that's me. But I thought you might want to send a v2 based on Kees'
>> comments?
> 
> Do you plan to follow up on this? I'd prefer if we could get rid of the open-
> coded "17". So, maybe just go with the define until we have something like
> STACK_FLEX_COUNT()?

Do you mean the following define...?

nv50_hdmi_enable(...)
{
...
#define data_len    17
     DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, data_len);
...rest of function...
#undef data_len
}

Thanks
--
Gustavo

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

Posted by Kees Cook 1 year, 4 months ago

>On 03/10/24 12:36, Danilo Krummrich wrote:
>> On 9/13/24 12:23 PM, Danilo Krummrich wrote:

I am reminded that I should check all my MUAs to render the date as YYYY-MM-DD so my brain doesn't explode when I see people "time traveling". ;)

(BTW, what MUAs do you both use? I use Mutt and K-9 Mail, and I need to check the quote prefix settings in both...)

-Kees

-- 
Kees Cook

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

Posted by Danilo Krummrich 1 year, 3 months ago

On Sat, Oct 05, 2024 at 09:04:11AM -0700, Kees Cook wrote:
> 
> 
> 
> >On 03/10/24 12:36, Danilo Krummrich wrote:
> >> On 9/13/24 12:23 PM, Danilo Krummrich wrote:
> 
> I am reminded that I should check all my MUAs to render the date as YYYY-MM-DD so my brain doesn't explode when I see people "time traveling". ;)
> 
> (BTW, what MUAs do you both use? I use Mutt and K-9 Mail, and I need to check the quote prefix settings in both...)

Mutt, and (unfortunately) Thunderbird for HTML stuff and a few other rare cases.

> 
> -Kees
> 
> -- 
> Kees Cook
>

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

Posted by Danilo Krummrich 1 year, 4 months ago

On 10/3/24 8:44 PM, Gustavo A. R. Silva wrote:
> 
> 
> On 03/10/24 12:36, Danilo Krummrich wrote:
>> On 9/13/24 12:23 PM, Danilo Krummrich wrote:
>>> Hi,
>>>
>>> On 9/13/24 10:09 AM, Gustavo A. R. Silva wrote:
>>>> Hi all,
>>>>
>>>> Friendly ping: who can take this, please? 🙂
>>>
>>> Usually, that's me. But I thought you might want to send a v2 based on Kees'
>>> comments?
>>
>> Do you plan to follow up on this? I'd prefer if we could get rid of the open-
>> coded "17". So, maybe just go with the define until we have something like
>> STACK_FLEX_COUNT()?
> 
> Do you mean the following define...?>
> nv50_hdmi_enable(...)
> {
> ...
> #define data_len    17
>      DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, data_len);
> ...rest of function...
> #undef data_len
> }

Yes, it's not great, but I think it's better than having the length in two
places.

> 
> Thanks
> -- 
> Gustavo
>

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

Posted by Gustavo A. R. Silva 1 year, 4 months ago

> 
> Yes, it's not great, but I think it's better than having the length in two
> places.

Agreed. I'll respin. :)

Thanks
--
Gustavo

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

Posted by Kees Cook 1 year, 5 months ago

On Wed, Aug 21, 2024 at 02:16:21PM -0600, Gustavo A. R. Silva wrote:
> 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 this, 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>
> ---
>  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 eed579a6c858..ddddc69640be 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
>  	struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>  	union hdmi_infoframe infoframe = { 0 };
>  	const u8 rekey = 56; /* binary driver, and tegra, constant */
> +	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
> +	const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */

To avoid repeating the open-coded "17", this could either be a define:

nv50_hdmi_enable(...)
{
...
#define data_len	17
	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, data_len);
...rest of function...
#undef data_len
}

or an ungainly but compile-time calculated value that exposes some
DEFINE_FLEX internals:

	const u8 data_len = (sizeof(args_u) - sizeof(*args)) / sizeof(*args->data);

(Maybe a helper is needed for that?)

#define STACK_FLEX_COUNT(name, member)	\
	((sizeof(name##_u) = sizeof(*(name))) / sizeof(*(name)->member))

> @@ -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;

The stack variable (was before and is again) already zero-initialized,
so the "= 0" line shouldn't be needed.

But neither of these comments are show-stoppers, IMO.

Reviewed-by: Kees Cook <kees@kernel.org>

-- 
Kees Cook

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

Posted by Gustavo A. R. Silva 1 year, 5 months ago


On 22/08/24 11:27, Kees Cook wrote:
> On Wed, Aug 21, 2024 at 02:16:21PM -0600, Gustavo A. R. Silva wrote:
>> 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 this, 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>
>> ---
>>   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 eed579a6c858..ddddc69640be 100644
>> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
>> @@ -774,11 +774,9 @@ nv50_hdmi_enable(struct drm_encoder *encoder, struct nouveau_crtc *nv_crtc,
>>   	struct drm_hdmi_info *hdmi = &nv_connector->base.display_info.hdmi;
>>   	union hdmi_infoframe infoframe = { 0 };
>>   	const u8 rekey = 56; /* binary driver, and tegra, constant */
>> +	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, 17);
>> +	const u8 data_len = 17; /* same length as in DEFINE_RAW_FLEX above. */
> 
> To avoid repeating the open-coded "17", this could either be a define:
> 
> nv50_hdmi_enable(...)
> {
> ...
> #define data_len	17
> 	DEFINE_RAW_FLEX(struct nvif_outp_infoframe_v0, args, data, data_len);
> ...rest of function...
> #undef data_len
> }
> 
> or an ungainly but compile-time calculated value that exposes some
> DEFINE_FLEX internals:
> 
> 	const u8 data_len = (sizeof(args_u) - sizeof(*args)) / sizeof(*args->data);

Yeah, I actually thought of something more like just __struct_size(args) - sizeof(*args),
as the flex array member is `__u8 data[]`.

> 
> (Maybe a helper is needed for that?)
> 
> #define STACK_FLEX_COUNT(name, member)	\
> 	((sizeof(name##_u) = sizeof(*(name))) / sizeof(*(name)->member))

I don't like this `sizeof(name##_u)` part as it is detached from the DEFINE_RAW_FLEX()
internals. Probably use `__struct_size(args)` instead, as in the example above.

> 
>> @@ -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;
> 
> The stack variable (was before and is again) already zero-initialized,
> so the "= 0" line shouldn't be needed.
> 
> But neither of these comments are show-stoppers, IMO.
> 
> Reviewed-by: Kees Cook <kees@kernel.org>
> 

Thanks!

--
Gustavo