[PATCH 0/3] drm/draw: add check API to avoid spurious WARN

[PATCH 0/3] drm/draw: add check API to avoid spurious WARN

[Francesco Valla]

When using the DRM draw support, the only way to check if a color can be
converted from XRGB8888 to a target format is currently to attempt an
actual conversion using drm_draw_color_from_xrgb8888(). This function
however will print a WARN the first time a conversion cannot be
performed, leading to two potential issues:

 - a WARN is emitted without a real reason if the caller is only
   attempting a conversion to check if a format can be supported (which
   is the case for two of the current user of this API);
 - a failing call following the first one is not emitting a WARN, but a
   "valid" color value (0x00000000) is returned nevertheless.

The first issue was observed while using drm_log on a Beagleplay, which
lists AR12 as the first format for its HDMI modesets.

The target of this patch set is to improve this situation; the first
patch introduces a new API devoted only to check if a conversion from
XRGB8888 to the specified format can be performed, while the other two
substitute drm_draw_color_from_xrgb8888() with this new API in the
current users (drm_panic and drm_log) where relevant.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
Francesco Valla (3):
      drm/draw: add drm_draw_can_convert_from_xrgb8888
      drm/log: avoid WARN when searching for usable format
      drm/log: avoid WARN when checking format support

 drivers/gpu/drm/clients/drm_log.c   |  2 +-
 drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
 drivers/gpu/drm/drm_draw_internal.h |  2 +
 drivers/gpu/drm/drm_panic.c         |  2 +-
 4 files changed, 65 insertions(+), 25 deletions(-)
---
base-commit: 7a405dbb0f036f8d1713ab9e7df0cd3137987b07
change-id: 20251003-drm_draw_conv_check-9cc3050ebd57

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

[PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Francesco Valla]

Add drm_draw_can_convert_from_xrgb8888() function that can be used to
determine if a XRGB8888 color can be converted to the specified format.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
 drivers/gpu/drm/drm_draw_internal.h |  2 +
 2 files changed, 63 insertions(+), 23 deletions(-)

diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..2641026a103d3b28cab9f5d378604b0604520fe4 100644
--- a/drivers/gpu/drm/drm_draw.c
+++ b/drivers/gpu/drm/drm_draw.c
@@ -15,45 +15,83 @@
 #include "drm_draw_internal.h"
 #include "drm_format_internal.h"
 
-/**
- * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
- * @color: input color, in xrgb8888 format
- * @format: output format
- *
- * Returns:
- * Color in the format specified, casted to u32.
- * Or 0 if the format is not supported.
- */
-u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
+static int __drm_draw_color_from_xrgb8888(u32 color, u32 format, u32 *out_color)
 {
 	switch (format) {
 	case DRM_FORMAT_RGB565:
-		return drm_pixel_xrgb8888_to_rgb565(color);
+		*out_color = drm_pixel_xrgb8888_to_rgb565(color);
+		break;
 	case DRM_FORMAT_RGBA5551:
-		return drm_pixel_xrgb8888_to_rgba5551(color);
+		*out_color = drm_pixel_xrgb8888_to_rgba5551(color);
+		break;
 	case DRM_FORMAT_XRGB1555:
-		return drm_pixel_xrgb8888_to_xrgb1555(color);
+		*out_color = drm_pixel_xrgb8888_to_xrgb1555(color);
+		break;
 	case DRM_FORMAT_ARGB1555:
-		return drm_pixel_xrgb8888_to_argb1555(color);
+		*out_color = drm_pixel_xrgb8888_to_argb1555(color);
+		break;
 	case DRM_FORMAT_RGB888:
+		fallthrough;
 	case DRM_FORMAT_XRGB8888:
-		return color;
+		*out_color = color;
+		break;
 	case DRM_FORMAT_ARGB8888:
-		return drm_pixel_xrgb8888_to_argb8888(color);
+		*out_color = drm_pixel_xrgb8888_to_argb8888(color);
+		break;
 	case DRM_FORMAT_XBGR8888:
-		return drm_pixel_xrgb8888_to_xbgr8888(color);
+		*out_color = drm_pixel_xrgb8888_to_xbgr8888(color);
+		break;
 	case DRM_FORMAT_ABGR8888:
-		return drm_pixel_xrgb8888_to_abgr8888(color);
+		*out_color = drm_pixel_xrgb8888_to_abgr8888(color);
+		break;
 	case DRM_FORMAT_XRGB2101010:
-		return drm_pixel_xrgb8888_to_xrgb2101010(color);
+		*out_color = drm_pixel_xrgb8888_to_xrgb2101010(color);
+		break;
 	case DRM_FORMAT_ARGB2101010:
-		return drm_pixel_xrgb8888_to_argb2101010(color);
+		*out_color = drm_pixel_xrgb8888_to_argb2101010(color);
+		break;
 	case DRM_FORMAT_ABGR2101010:
-		return drm_pixel_xrgb8888_to_abgr2101010(color);
+		*out_color = drm_pixel_xrgb8888_to_abgr2101010(color);
+		break;
 	default:
-		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
-		return 0;
+		return -1;
 	}
+
+	return 0;
+}
+
+/**
+ * drm_draw_can_convert_from_xrgb8888 - check if xrgb8888 can be converted to the desired format
+ * @format: format
+ *
+ * Returns:
+ * True if XRGB8888 can be converted to the specified format, false otherwise.
+ */
+bool drm_draw_can_convert_from_xrgb8888(u32 format)
+{
+	u32 out_color;
+
+	return __drm_draw_color_from_xrgb8888(0, format, &out_color) == 0;
+}
+EXPORT_SYMBOL(drm_draw_can_convert_from_xrgb8888);
+
+/**
+ * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
+ * @color: input color, in xrgb8888 format
+ * @format: output format
+ *
+ * Returns:
+ * Color in the format specified, casted to u32.
+ * Or 0 if the format is not supported.
+ */
+u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
+{
+	u32 out_color = 0;
+
+	if (__drm_draw_color_from_xrgb8888(color, format, &out_color))
+		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
+
+	return out_color;
 }
 EXPORT_SYMBOL(drm_draw_color_from_xrgb8888);
 
diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
index f121ee7339dc11537f677c833f0ee94fe0e799cd..2ab4cb341df94fc4173dd6f5e7a512bdcfa5e55c 100644
--- a/drivers/gpu/drm/drm_draw_internal.h
+++ b/drivers/gpu/drm/drm_draw_internal.h
@@ -24,6 +24,8 @@ static inline const u8 *drm_draw_get_char_bitmap(const struct font_desc *font,
 	return font->data + (c * font->height) * font_pitch;
 }
 
+bool drm_draw_can_convert_from_xrgb8888(u32 format);
+
 u32 drm_draw_color_from_xrgb8888(u32 color, u32 format);
 
 void drm_draw_blit16(struct iosys_map *dmap, unsigned int dpitch,

-- 
2.51.0

Re: [PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Jani Nikula]

On Sun, 05 Oct 2025, Francesco Valla <francesco@valla.it> wrote:
> Add drm_draw_can_convert_from_xrgb8888() function that can be used to
> determine if a XRGB8888 color can be converted to the specified format.
>
> Signed-off-by: Francesco Valla <francesco@valla.it>
> ---
>  drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
>  drivers/gpu/drm/drm_draw_internal.h |  2 +
>  2 files changed, 63 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..2641026a103d3b28cab9f5d378604b0604520fe4 100644
> --- a/drivers/gpu/drm/drm_draw.c
> +++ b/drivers/gpu/drm/drm_draw.c
> @@ -15,45 +15,83 @@
>  #include "drm_draw_internal.h"
>  #include "drm_format_internal.h"
>  
> -/**
> - * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
> - * @color: input color, in xrgb8888 format
> - * @format: output format
> - *
> - * Returns:
> - * Color in the format specified, casted to u32.
> - * Or 0 if the format is not supported.
> - */
> -u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
> +static int __drm_draw_color_from_xrgb8888(u32 color, u32 format, u32 *out_color)

Is there any reason to change the return value of this function and
return the result via out_color? It already returns 0 if the format is
not supported. If there's a reason, it needs to be in the commit
message.

>  {
>  	switch (format) {
>  	case DRM_FORMAT_RGB565:
> -		return drm_pixel_xrgb8888_to_rgb565(color);
> +		*out_color = drm_pixel_xrgb8888_to_rgb565(color);
> +		break;
>  	case DRM_FORMAT_RGBA5551:
> -		return drm_pixel_xrgb8888_to_rgba5551(color);
> +		*out_color = drm_pixel_xrgb8888_to_rgba5551(color);
> +		break;
>  	case DRM_FORMAT_XRGB1555:
> -		return drm_pixel_xrgb8888_to_xrgb1555(color);
> +		*out_color = drm_pixel_xrgb8888_to_xrgb1555(color);
> +		break;
>  	case DRM_FORMAT_ARGB1555:
> -		return drm_pixel_xrgb8888_to_argb1555(color);
> +		*out_color = drm_pixel_xrgb8888_to_argb1555(color);
> +		break;
>  	case DRM_FORMAT_RGB888:
> +		fallthrough;

That's not necessary for back to back case labels. Please don't add it.

>  	case DRM_FORMAT_XRGB8888:
> -		return color;
> +		*out_color = color;
> +		break;
>  	case DRM_FORMAT_ARGB8888:
> -		return drm_pixel_xrgb8888_to_argb8888(color);
> +		*out_color = drm_pixel_xrgb8888_to_argb8888(color);
> +		break;
>  	case DRM_FORMAT_XBGR8888:
> -		return drm_pixel_xrgb8888_to_xbgr8888(color);
> +		*out_color = drm_pixel_xrgb8888_to_xbgr8888(color);
> +		break;
>  	case DRM_FORMAT_ABGR8888:
> -		return drm_pixel_xrgb8888_to_abgr8888(color);
> +		*out_color = drm_pixel_xrgb8888_to_abgr8888(color);
> +		break;
>  	case DRM_FORMAT_XRGB2101010:
> -		return drm_pixel_xrgb8888_to_xrgb2101010(color);
> +		*out_color = drm_pixel_xrgb8888_to_xrgb2101010(color);
> +		break;
>  	case DRM_FORMAT_ARGB2101010:
> -		return drm_pixel_xrgb8888_to_argb2101010(color);
> +		*out_color = drm_pixel_xrgb8888_to_argb2101010(color);
> +		break;
>  	case DRM_FORMAT_ABGR2101010:
> -		return drm_pixel_xrgb8888_to_abgr2101010(color);
> +		*out_color = drm_pixel_xrgb8888_to_abgr2101010(color);
> +		break;
>  	default:
> -		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
> -		return 0;
> +		return -1;

Please don't use -1 as a generic error code. -1 is -EPERM.

>  	}
> +
> +	return 0;
> +}
> +
> +/**
> + * drm_draw_can_convert_from_xrgb8888 - check if xrgb8888 can be converted to the desired format
> + * @format: format
> + *
> + * Returns:
> + * True if XRGB8888 can be converted to the specified format, false otherwise.
> + */
> +bool drm_draw_can_convert_from_xrgb8888(u32 format)
> +{
> +	u32 out_color;
> +
> +	return __drm_draw_color_from_xrgb8888(0, format, &out_color) == 0;
> +}
> +EXPORT_SYMBOL(drm_draw_can_convert_from_xrgb8888);
> +
> +/**
> + * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
> + * @color: input color, in xrgb8888 format
> + * @format: output format
> + *
> + * Returns:
> + * Color in the format specified, casted to u32.
> + * Or 0 if the format is not supported.
> + */
> +u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
> +{
> +	u32 out_color = 0;
> +
> +	if (__drm_draw_color_from_xrgb8888(color, format, &out_color))
> +		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
> +
> +	return out_color;
>  }
>  EXPORT_SYMBOL(drm_draw_color_from_xrgb8888);
>  
> diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
> index f121ee7339dc11537f677c833f0ee94fe0e799cd..2ab4cb341df94fc4173dd6f5e7a512bdcfa5e55c 100644
> --- a/drivers/gpu/drm/drm_draw_internal.h
> +++ b/drivers/gpu/drm/drm_draw_internal.h
> @@ -24,6 +24,8 @@ static inline const u8 *drm_draw_get_char_bitmap(const struct font_desc *font,
>  	return font->data + (c * font->height) * font_pitch;
>  }
>  
> +bool drm_draw_can_convert_from_xrgb8888(u32 format);
> +
>  u32 drm_draw_color_from_xrgb8888(u32 color, u32 format);
>  
>  void drm_draw_blit16(struct iosys_map *dmap, unsigned int dpitch,

-- 
Jani Nikula, Intel

Re: [PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Jocelyn Falempe]

On 10/6/25 08:48, Jani Nikula wrote:
> On Sun, 05 Oct 2025, Francesco Valla <francesco@valla.it> wrote:
>> Add drm_draw_can_convert_from_xrgb8888() function that can be used to
>> determine if a XRGB8888 color can be converted to the specified format.
>>
>> Signed-off-by: Francesco Valla <francesco@valla.it>
>> ---
>>   drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
>>   drivers/gpu/drm/drm_draw_internal.h |  2 +
>>   2 files changed, 63 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
>> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..2641026a103d3b28cab9f5d378604b0604520fe4 100644
>> --- a/drivers/gpu/drm/drm_draw.c
>> +++ b/drivers/gpu/drm/drm_draw.c
>> @@ -15,45 +15,83 @@
>>   #include "drm_draw_internal.h"
>>   #include "drm_format_internal.h"
>>   
>> -/**
>> - * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
>> - * @color: input color, in xrgb8888 format
>> - * @format: output format
>> - *
>> - * Returns:
>> - * Color in the format specified, casted to u32.
>> - * Or 0 if the format is not supported.
>> - */
>> -u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
>> +static int __drm_draw_color_from_xrgb8888(u32 color, u32 format, u32 *out_color)
> 
> Is there any reason to change the return value of this function and
> return the result via out_color? It already returns 0 if the format is
> not supported. If there's a reason, it needs to be in the commit
> message.

I think the problem is that 0, is also a valid color.

Maybe it would be better to split it into 2 functions, and duplicate the 
switch case.

ie:

u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
{
	switch(format) {
	case DRM_FORMAT_RGB565:
		return drm_pixel_xrgb8888_to_rgb565(color);

....


bool drm_draw_can_convert_from_xrgb8888(u32 format)
{

	switch(format) {
	case DRM_FORMAT_RGB565:
		return true;

....
	default:
		return false;


I didn't do it this way, because there is a risk to add a format to only 
one of the switch. But after more thinking, that would be simpler overall.

Best regards,

-- 

Jocelyn


> 
>>   {
>>   	switch (format) {
>>   	case DRM_FORMAT_RGB565:
>> -		return drm_pixel_xrgb8888_to_rgb565(color);
>> +		*out_color = drm_pixel_xrgb8888_to_rgb565(color);
>> +		break;
>>   	case DRM_FORMAT_RGBA5551:
>> -		return drm_pixel_xrgb8888_to_rgba5551(color);
>> +		*out_color = drm_pixel_xrgb8888_to_rgba5551(color);
>> +		break;
>>   	case DRM_FORMAT_XRGB1555:
>> -		return drm_pixel_xrgb8888_to_xrgb1555(color);
>> +		*out_color = drm_pixel_xrgb8888_to_xrgb1555(color);
>> +		break;
>>   	case DRM_FORMAT_ARGB1555:
>> -		return drm_pixel_xrgb8888_to_argb1555(color);
>> +		*out_color = drm_pixel_xrgb8888_to_argb1555(color);
>> +		break;
>>   	case DRM_FORMAT_RGB888:
>> +		fallthrough;
> 
> That's not necessary for back to back case labels. Please don't add it.
> 
>>   	case DRM_FORMAT_XRGB8888:
>> -		return color;
>> +		*out_color = color;
>> +		break;
>>   	case DRM_FORMAT_ARGB8888:
>> -		return drm_pixel_xrgb8888_to_argb8888(color);
>> +		*out_color = drm_pixel_xrgb8888_to_argb8888(color);
>> +		break;
>>   	case DRM_FORMAT_XBGR8888:
>> -		return drm_pixel_xrgb8888_to_xbgr8888(color);
>> +		*out_color = drm_pixel_xrgb8888_to_xbgr8888(color);
>> +		break;
>>   	case DRM_FORMAT_ABGR8888:
>> -		return drm_pixel_xrgb8888_to_abgr8888(color);
>> +		*out_color = drm_pixel_xrgb8888_to_abgr8888(color);
>> +		break;
>>   	case DRM_FORMAT_XRGB2101010:
>> -		return drm_pixel_xrgb8888_to_xrgb2101010(color);
>> +		*out_color = drm_pixel_xrgb8888_to_xrgb2101010(color);
>> +		break;
>>   	case DRM_FORMAT_ARGB2101010:
>> -		return drm_pixel_xrgb8888_to_argb2101010(color);
>> +		*out_color = drm_pixel_xrgb8888_to_argb2101010(color);
>> +		break;
>>   	case DRM_FORMAT_ABGR2101010:
>> -		return drm_pixel_xrgb8888_to_abgr2101010(color);
>> +		*out_color = drm_pixel_xrgb8888_to_abgr2101010(color);
>> +		break;
>>   	default:
>> -		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
>> -		return 0;
>> +		return -1;
> 
> Please don't use -1 as a generic error code. -1 is -EPERM.
> 
>>   	}
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * drm_draw_can_convert_from_xrgb8888 - check if xrgb8888 can be converted to the desired format
>> + * @format: format
>> + *
>> + * Returns:
>> + * True if XRGB8888 can be converted to the specified format, false otherwise.
>> + */
>> +bool drm_draw_can_convert_from_xrgb8888(u32 format)
>> +{
>> +	u32 out_color;
>> +
>> +	return __drm_draw_color_from_xrgb8888(0, format, &out_color) == 0;
>> +}
>> +EXPORT_SYMBOL(drm_draw_can_convert_from_xrgb8888);
>> +
>> +/**
>> + * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
>> + * @color: input color, in xrgb8888 format
>> + * @format: output format
>> + *
>> + * Returns:
>> + * Color in the format specified, casted to u32.
>> + * Or 0 if the format is not supported.
>> + */
>> +u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
>> +{
>> +	u32 out_color = 0;
>> +
>> +	if (__drm_draw_color_from_xrgb8888(color, format, &out_color))
>> +		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
>> +
>> +	return out_color;
>>   }
>>   EXPORT_SYMBOL(drm_draw_color_from_xrgb8888);
>>   
>> diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
>> index f121ee7339dc11537f677c833f0ee94fe0e799cd..2ab4cb341df94fc4173dd6f5e7a512bdcfa5e55c 100644
>> --- a/drivers/gpu/drm/drm_draw_internal.h
>> +++ b/drivers/gpu/drm/drm_draw_internal.h
>> @@ -24,6 +24,8 @@ static inline const u8 *drm_draw_get_char_bitmap(const struct font_desc *font,
>>   	return font->data + (c * font->height) * font_pitch;
>>   }
>>   
>> +bool drm_draw_can_convert_from_xrgb8888(u32 format);
>> +
>>   u32 drm_draw_color_from_xrgb8888(u32 color, u32 format);
>>   
>>   void drm_draw_blit16(struct iosys_map *dmap, unsigned int dpitch,
> 

Re: [PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Jani Nikula]

On Mon, 06 Oct 2025, Jocelyn Falempe <jfalempe@redhat.com> wrote:
> On 10/6/25 08:48, Jani Nikula wrote:
>> On Sun, 05 Oct 2025, Francesco Valla <francesco@valla.it> wrote:
>>> Add drm_draw_can_convert_from_xrgb8888() function that can be used to
>>> determine if a XRGB8888 color can be converted to the specified format.
>>>
>>> Signed-off-by: Francesco Valla <francesco@valla.it>
>>> ---
>>>   drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
>>>   drivers/gpu/drm/drm_draw_internal.h |  2 +
>>>   2 files changed, 63 insertions(+), 23 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
>>> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..2641026a103d3b28cab9f5d378604b0604520fe4 100644
>>> --- a/drivers/gpu/drm/drm_draw.c
>>> +++ b/drivers/gpu/drm/drm_draw.c
>>> @@ -15,45 +15,83 @@
>>>   #include "drm_draw_internal.h"
>>>   #include "drm_format_internal.h"
>>>   
>>> -/**
>>> - * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
>>> - * @color: input color, in xrgb8888 format
>>> - * @format: output format
>>> - *
>>> - * Returns:
>>> - * Color in the format specified, casted to u32.
>>> - * Or 0 if the format is not supported.
>>> - */
>>> -u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
>>> +static int __drm_draw_color_from_xrgb8888(u32 color, u32 format, u32 *out_color)
>> 
>> Is there any reason to change the return value of this function and
>> return the result via out_color? It already returns 0 if the format is
>> not supported. If there's a reason, it needs to be in the commit
>> message.
>
> I think the problem is that 0, is also a valid color.

Right, of course.

> Maybe it would be better to split it into 2 functions, and duplicate the 
> switch case.
>
> ie:
>
> u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
> {
> 	switch(format) {
> 	case DRM_FORMAT_RGB565:
> 		return drm_pixel_xrgb8888_to_rgb565(color);
>
> ....
>
>
> bool drm_draw_can_convert_from_xrgb8888(u32 format)
> {
>
> 	switch(format) {
> 	case DRM_FORMAT_RGB565:
> 		return true;
>
> ....
> 	default:
> 		return false;
>
>
> I didn't do it this way, because there is a risk to add a format to only 
> one of the switch. But after more thinking, that would be simpler overall.

The duplication is a bit annoying, but it might be simpler. Dunno.

BR,
Jani.




>
> Best regards,

-- 
Jani Nikula, Intel

Re: [PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Francesco Valla]

On Monday, 6 October 2025 at 08:48:51 Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Sun, 05 Oct 2025, Francesco Valla <francesco@valla.it> wrote:
> > Add drm_draw_can_convert_from_xrgb8888() function that can be used to
> > determine if a XRGB8888 color can be converted to the specified format.
> >
> > Signed-off-by: Francesco Valla <francesco@valla.it>
> > ---
> >  drivers/gpu/drm/drm_draw.c          | 84 +++++++++++++++++++++++++++----------
> >  drivers/gpu/drm/drm_draw_internal.h |  2 +
> >  2 files changed, 63 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
> > index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..2641026a103d3b28cab9f5d378604b0604520fe4 100644
> > --- a/drivers/gpu/drm/drm_draw.c
> > +++ b/drivers/gpu/drm/drm_draw.c
> > @@ -15,45 +15,83 @@
> >  #include "drm_draw_internal.h"
> >  #include "drm_format_internal.h"
> >  
> > -/**
> > - * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
> > - * @color: input color, in xrgb8888 format
> > - * @format: output format
> > - *
> > - * Returns:
> > - * Color in the format specified, casted to u32.
> > - * Or 0 if the format is not supported.
> > - */
> > -u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
> > +static int __drm_draw_color_from_xrgb8888(u32 color, u32 format, u32 *out_color)
> 
> Is there any reason to change the return value of this function and
> return the result via out_color? It already returns 0 if the format is
> not supported. If there's a reason, it needs to be in the commit
> message.
> 

Is because 0 might be a valid color (e.g black for RGB888), as Jocelyn
correctly pointed out in another thread. I'll add this detail to the
commit message for the V2.

> >  {
> >  	switch (format) {
> >  	case DRM_FORMAT_RGB565:
> > -		return drm_pixel_xrgb8888_to_rgb565(color);
> > +		*out_color = drm_pixel_xrgb8888_to_rgb565(color);
> > +		break;
> >  	case DRM_FORMAT_RGBA5551:
> > -		return drm_pixel_xrgb8888_to_rgba5551(color);
> > +		*out_color = drm_pixel_xrgb8888_to_rgba5551(color);
> > +		break;
> >  	case DRM_FORMAT_XRGB1555:
> > -		return drm_pixel_xrgb8888_to_xrgb1555(color);
> > +		*out_color = drm_pixel_xrgb8888_to_xrgb1555(color);
> > +		break;
> >  	case DRM_FORMAT_ARGB1555:
> > -		return drm_pixel_xrgb8888_to_argb1555(color);
> > +		*out_color = drm_pixel_xrgb8888_to_argb1555(color);
> > +		break;
> >  	case DRM_FORMAT_RGB888:
> > +		fallthrough;
> 
> That's not necessary for back to back case labels. Please don't add it.
>

Noted.

> >  	case DRM_FORMAT_XRGB8888:
> > -		return color;
> > +		*out_color = color;
> > +		break;
> >  	case DRM_FORMAT_ARGB8888:
> > -		return drm_pixel_xrgb8888_to_argb8888(color);
> > +		*out_color = drm_pixel_xrgb8888_to_argb8888(color);
> > +		break;
> >  	case DRM_FORMAT_XBGR8888:
> > -		return drm_pixel_xrgb8888_to_xbgr8888(color);
> > +		*out_color = drm_pixel_xrgb8888_to_xbgr8888(color);
> > +		break;
> >  	case DRM_FORMAT_ABGR8888:
> > -		return drm_pixel_xrgb8888_to_abgr8888(color);
> > +		*out_color = drm_pixel_xrgb8888_to_abgr8888(color);
> > +		break;
> >  	case DRM_FORMAT_XRGB2101010:
> > -		return drm_pixel_xrgb8888_to_xrgb2101010(color);
> > +		*out_color = drm_pixel_xrgb8888_to_xrgb2101010(color);
> > +		break;
> >  	case DRM_FORMAT_ARGB2101010:
> > -		return drm_pixel_xrgb8888_to_argb2101010(color);
> > +		*out_color = drm_pixel_xrgb8888_to_argb2101010(color);
> > +		break;
> >  	case DRM_FORMAT_ABGR2101010:
> > -		return drm_pixel_xrgb8888_to_abgr2101010(color);
> > +		*out_color = drm_pixel_xrgb8888_to_abgr2101010(color);
> > +		break;
> >  	default:
> > -		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
> > -		return 0;
> > +		return -1;
> 
> Please don't use -1 as a generic error code. -1 is -EPERM.
> 

Whops, you're right. I'll return -ENOTSUPP.

> >  	}
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * drm_draw_can_convert_from_xrgb8888 - check if xrgb8888 can be converted to the desired format
> > + * @format: format
> > + *
> > + * Returns:
> > + * True if XRGB8888 can be converted to the specified format, false otherwise.
> > + */
> > +bool drm_draw_can_convert_from_xrgb8888(u32 format)
> > +{
> > +	u32 out_color;
> > +
> > +	return __drm_draw_color_from_xrgb8888(0, format, &out_color) == 0;
> > +}
> > +EXPORT_SYMBOL(drm_draw_can_convert_from_xrgb8888);
> > +
> > +/**
> > + * drm_draw_color_from_xrgb8888 - convert one pixel from xrgb8888 to the desired format
> > + * @color: input color, in xrgb8888 format
> > + * @format: output format
> > + *
> > + * Returns:
> > + * Color in the format specified, casted to u32.
> > + * Or 0 if the format is not supported.
> > + */
> > +u32 drm_draw_color_from_xrgb8888(u32 color, u32 format)
> > +{
> > +	u32 out_color = 0;
> > +
> > +	if (__drm_draw_color_from_xrgb8888(color, format, &out_color))
> > +		WARN_ONCE(1, "Can't convert to %p4cc\n", &format);
> > +
> > +	return out_color;
> >  }
> >  EXPORT_SYMBOL(drm_draw_color_from_xrgb8888);
> >  
> > diff --git a/drivers/gpu/drm/drm_draw_internal.h b/drivers/gpu/drm/drm_draw_internal.h
> > index f121ee7339dc11537f677c833f0ee94fe0e799cd..2ab4cb341df94fc4173dd6f5e7a512bdcfa5e55c 100644
> > --- a/drivers/gpu/drm/drm_draw_internal.h
> > +++ b/drivers/gpu/drm/drm_draw_internal.h
> > @@ -24,6 +24,8 @@ static inline const u8 *drm_draw_get_char_bitmap(const struct font_desc *font,
> >  	return font->data + (c * font->height) * font_pitch;
> >  }
> >  
> > +bool drm_draw_can_convert_from_xrgb8888(u32 format);
> > +
> >  u32 drm_draw_color_from_xrgb8888(u32 color, u32 format);
> >  
> >  void drm_draw_blit16(struct iosys_map *dmap, unsigned int dpitch,
> 
> 

Thank you.

Best regards,

--

Francesco

[PATCH 2/3] drm/log: avoid WARN when searching for usable format

[Francesco Valla]

Use drm_draw_can_convert_from_xrgb8888() instead of
drm_draw_color_from_xrgb8888() while searching for a usable color
format. This avoids a WARN in case the first format is not usable.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/gpu/drm/clients/drm_log.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c
index d239f1e3c456397ad64007b20dde716f5d3d0881..c0150f0c3b4b395e6e2126cf0d9660c967c182ec 100644
--- a/drivers/gpu/drm/clients/drm_log.c
+++ b/drivers/gpu/drm/clients/drm_log.c
@@ -182,7 +182,7 @@ static u32 drm_log_find_usable_format(struct drm_plane *plane)
 	int i;
 
 	for (i = 0; i < plane->format_count; i++)
-		if (drm_draw_color_from_xrgb8888(0xffffff, plane->format_types[i]) != 0)
+		if (drm_draw_can_convert_from_xrgb8888(plane->format_types[i]))
 			return plane->format_types[i];
 	return DRM_FORMAT_INVALID;
 }

-- 
2.51.0

[PATCH 3/3] drm/log: avoid WARN when checking format support

[Francesco Valla]

Use drm_draw_can_convert_from_xrgb8888() instead of
drm_draw_color_from_xrgb8888() while checking if a color format is
usable. This avoids a WARN in case the first format is not usable.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/gpu/drm/drm_panic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 1d6312fa142935fcf763381920ad889ca4cf4b27..4ba961e445e576d03cfb58953eead90d32b40151 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -785,7 +785,7 @@ static bool drm_panic_is_format_supported(const struct drm_format_info *format)
 {
 	if (format->num_planes != 1)
 		return false;
-	return drm_draw_color_from_xrgb8888(0xffffff, format->format) != 0;
+	return drm_draw_can_convert_from_xrgb8888(format->format);
 }
 
 static void draw_panic_dispatch(struct drm_scanout_buffer *sb)

-- 
2.51.0