[PATCH] drm/draw: fix color truncation in drm_draw_fill24

[PATCH] drm/draw: fix color truncation in drm_draw_fill24

[Francesco Valla]

The color parameter passed to drm_draw_fill24() was truncated to 16
bits, leading to an incorrect color drawn to the target iosys_map.
Fix this behavior, widening the parameter to 32 bits.

Fixes: 31fa2c1ca0b2 ("drm/panic: Move drawing functions to drm_draw")

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/gpu/drm/drm_draw.c          | 2 +-
 drivers/gpu/drm/drm_draw_internal.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..5b956229c82fb6e232e3342705a226c8e14c8568 100644
--- a/drivers/gpu/drm/drm_draw.c
+++ b/drivers/gpu/drm/drm_draw.c
@@ -127,7 +127,7 @@ EXPORT_SYMBOL(drm_draw_fill16);
 
 void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
 		     unsigned int height, unsigned int width,
-		     u16 color)
+		     u32 color)
 {
 	unsigned int y, x;
 
diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
index f121ee7339dc11537f677c833f0ee94fe0e799cd..20cb404e23ea6263b535ea2b81b25f84c37be8a2 100644
--- a/drivers/gpu/drm/drm_draw_internal.h
+++ b/drivers/gpu/drm/drm_draw_internal.h
@@ -47,7 +47,7 @@ void drm_draw_fill16(struct iosys_map *dmap, unsigned int dpitch,
 
 void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
 		     unsigned int height, unsigned int width,
-		     u16 color);
+		     u32 color);
 
 void drm_draw_fill32(struct iosys_map *dmap, unsigned int dpitch,
 		     unsigned int height, unsigned int width,

---
base-commit: e406d57be7bd2a4e73ea512c1ae36a40a44e499e
change-id: 20251003-drm_draw_fill24_fix-ea52d32a933d

Best regards,
-- 
Francesco Valla <francesco@valla.it>

Re: [PATCH] drm/draw: fix color truncation in drm_draw_fill24

[Jocelyn Falempe]

On 10/3/25 12:33, Francesco Valla wrote:
> The color parameter passed to drm_draw_fill24() was truncated to 16
> bits, leading to an incorrect color drawn to the target iosys_map.
> Fix this behavior, widening the parameter to 32 bits.
> 
Oh, you're right, my mistake.
Did you find this by using a 24bit hardware, or by looking at the code?

Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>

Best regards,

-- 

Jocelyn

> Fixes: 31fa2c1ca0b2 ("drm/panic: Move drawing functions to drm_draw")
> 
> Signed-off-by: Francesco Valla <francesco@valla.it>
> ---
>   drivers/gpu/drm/drm_draw.c          | 2 +-
>   drivers/gpu/drm/drm_draw_internal.h | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..5b956229c82fb6e232e3342705a226c8e14c8568 100644
> --- a/drivers/gpu/drm/drm_draw.c
> +++ b/drivers/gpu/drm/drm_draw.c
> @@ -127,7 +127,7 @@ EXPORT_SYMBOL(drm_draw_fill16);
>   
>   void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> -		     u16 color)
> +		     u32 color)
>   {
>   	unsigned int y, x;
>   
> diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
> index f121ee7339dc11537f677c833f0ee94fe0e799cd..20cb404e23ea6263b535ea2b81b25f84c37be8a2 100644
> --- a/drivers/gpu/drm/drm_draw_internal.h
> +++ b/drivers/gpu/drm/drm_draw_internal.h
> @@ -47,7 +47,7 @@ void drm_draw_fill16(struct iosys_map *dmap, unsigned int dpitch,
>   
>   void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> -		     u16 color);
> +		     u32 color);
>   
>   void drm_draw_fill32(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> 
> ---
> base-commit: e406d57be7bd2a4e73ea512c1ae36a40a44e499e
> change-id: 20251003-drm_draw_fill24_fix-ea52d32a933d
> 
> Best regards,

Re: [PATCH] drm/draw: fix color truncation in drm_draw_fill24

[Francesco Valla]

Hi Jocelyn,

On Friday, 3 October 2025 at 14:48:03 Jocelyn Falempe <jfalempe@redhat.com> wrote:
> On 10/3/25 12:33, Francesco Valla wrote:
> > The color parameter passed to drm_draw_fill24() was truncated to 16
> > bits, leading to an incorrect color drawn to the target iosys_map.
> > Fix this behavior, widening the parameter to 32 bits.
> > 
> Oh, you're right, my mistake.
> Did you find this by using a 24bit hardware, or by looking at the code?
> 
> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
> 
> Best regards,
> 

I am working on a graphical splash DRM client (which I hope I'll be
able to post soon) and testing it on a Beagleplay - which is
RG24-capable - I started to see a strange behavior with non-black
colors. After some investigation I found the cuplrit, and strangely
enough it wasn't me this time.

Best regards,

Francesco

Re: [PATCH] drm/draw: fix color truncation in drm_draw_fill24

[Jocelyn Falempe]

On 10/3/25 16:41, Francesco Valla wrote:
> Hi Jocelyn,
> 
> On Friday, 3 October 2025 at 14:48:03 Jocelyn Falempe <jfalempe@redhat.com> wrote:
>> On 10/3/25 12:33, Francesco Valla wrote:
>>> The color parameter passed to drm_draw_fill24() was truncated to 16
>>> bits, leading to an incorrect color drawn to the target iosys_map.
>>> Fix this behavior, widening the parameter to 32 bits.
>>>
>> Oh, you're right, my mistake.
>> Did you find this by using a 24bit hardware, or by looking at the code?
>>
>> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
>>
>> Best regards,
>>
> 
> I am working on a graphical splash DRM client (which I hope I'll be
> able to post soon) and testing it on a Beagleplay - which is
> RG24-capable - I started to see a strange behavior with non-black
> colors. After some investigation I found the cuplrit, and strangely
> enough it wasn't me this time.

Thanks, I was wondering if this 24bit code would see a real usage, so it 
looks like this is still a thing in 2025.

Best regards,

-- 

Jocelyn

> 
> Best regards,
> 
> Francesco
> 
> 
> 
> 
> 
> 

Re: [PATCH] drm/draw: fix color truncation in drm_draw_fill24

[Jocelyn Falempe]

On 03/10/2025 12:33, Francesco Valla wrote:
> The color parameter passed to drm_draw_fill24() was truncated to 16
> bits, leading to an incorrect color drawn to the target iosys_map.
> Fix this behavior, widening the parameter to 32 bits.

Merged to drm-misc-fixes.

Thanks for your contribution.

-- 

Jocelyn

> 
> Fixes: 31fa2c1ca0b2 ("drm/panic: Move drawing functions to drm_draw")
> 
> Signed-off-by: Francesco Valla <francesco@valla.it>
> ---
>   drivers/gpu/drm/drm_draw.c          | 2 +-
>   drivers/gpu/drm/drm_draw_internal.h | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..5b956229c82fb6e232e3342705a226c8e14c8568 100644
> --- a/drivers/gpu/drm/drm_draw.c
> +++ b/drivers/gpu/drm/drm_draw.c
> @@ -127,7 +127,7 @@ EXPORT_SYMBOL(drm_draw_fill16);
>   
>   void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> -		     u16 color)
> +		     u32 color)
>   {
>   	unsigned int y, x;
>   
> diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
> index f121ee7339dc11537f677c833f0ee94fe0e799cd..20cb404e23ea6263b535ea2b81b25f84c37be8a2 100644
> --- a/drivers/gpu/drm/drm_draw_internal.h
> +++ b/drivers/gpu/drm/drm_draw_internal.h
> @@ -47,7 +47,7 @@ void drm_draw_fill16(struct iosys_map *dmap, unsigned int dpitch,
>   
>   void drm_draw_fill24(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> -		     u16 color);
> +		     u32 color);
>   
>   void drm_draw_fill32(struct iosys_map *dmap, unsigned int dpitch,
>   		     unsigned int height, unsigned int width,
> 
> ---
> base-commit: e406d57be7bd2a4e73ea512c1ae36a40a44e499e
> change-id: 20251003-drm_draw_fill24_fix-ea52d32a933d
> 
> Best regards,