[PATCH v2 0/3] drm/draw: add check API to avoid spurious WARN

[PATCH v2 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>
---
Changes in v2:
- Moved to dedicated switch cases in separate functions instead of
  single one inside common function.
- Fix copy-paste error in commit message.

Link to v1: https://lore.kernel.org/r/20251005-drm_draw_conv_check-v1-0-9c814d9362f6@valla.it

---
Francesco Valla (3):
      drm/draw: add drm_draw_can_convert_from_xrgb8888
      drm/log: avoid WARN when searching for usable format
      drm/panic: avoid WARN when checking format support

 drivers/gpu/drm/clients/drm_log.c   |  2 +-
 drivers/gpu/drm/drm_draw.c          | 29 +++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_draw_internal.h |  2 ++
 drivers/gpu/drm/drm_panic.c         |  2 +-
 4 files changed, 33 insertions(+), 2 deletions(-)
---
base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
change-id: 20251003-drm_draw_conv_check-9cc3050ebd57

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

[PATCH v2 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          | 29 +++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_draw_internal.h |  2 ++
 2 files changed, 31 insertions(+)

diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..ccdd6b16e73fc01d58f45759cf3824be7aac155b 100644
--- a/drivers/gpu/drm/drm_draw.c
+++ b/drivers/gpu/drm/drm_draw.c
@@ -15,6 +15,35 @@
 #include "drm_draw_internal.h"
 #include "drm_format_internal.h"
 
+/**
+ * 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)
+{
+	switch (format) {
+	case DRM_FORMAT_RGB565:
+	case DRM_FORMAT_RGBA5551:
+	case DRM_FORMAT_XRGB1555:
+	case DRM_FORMAT_ARGB1555:
+	case DRM_FORMAT_RGB888:
+	case DRM_FORMAT_XRGB8888:
+	case DRM_FORMAT_ARGB8888:
+	case DRM_FORMAT_XBGR8888:
+	case DRM_FORMAT_ABGR8888:
+	case DRM_FORMAT_XRGB2101010:
+	case DRM_FORMAT_ARGB2101010:
+	case DRM_FORMAT_ABGR2101010:
+		return true;
+	default:
+		return false;
+	}
+}
+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
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

[PATCH v2 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 v2 3/3] drm/panic: 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

Re: [PATCH v2 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888

[Jocelyn Falempe]

On 14/10/2025 22:08, Francesco Valla 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.

Thanks for the v2, it looks good to me.

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

> 
> Signed-off-by: Francesco Valla <francesco@valla.it>
> ---
>   drivers/gpu/drm/drm_draw.c          | 29 +++++++++++++++++++++++++++++
>   drivers/gpu/drm/drm_draw_internal.h |  2 ++
>   2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_draw.c b/drivers/gpu/drm/drm_draw.c
> index 9dc0408fbbeadbe8282a2d6b210e0bfb0672967f..ccdd6b16e73fc01d58f45759cf3824be7aac155b 100644
> --- a/drivers/gpu/drm/drm_draw.c
> +++ b/drivers/gpu/drm/drm_draw.c
> @@ -15,6 +15,35 @@
>   #include "drm_draw_internal.h"
>   #include "drm_format_internal.h"
>   
> +/**
> + * 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)
> +{
> +	switch (format) {
> +	case DRM_FORMAT_RGB565:
> +	case DRM_FORMAT_RGBA5551:
> +	case DRM_FORMAT_XRGB1555:
> +	case DRM_FORMAT_ARGB1555:
> +	case DRM_FORMAT_RGB888:
> +	case DRM_FORMAT_XRGB8888:
> +	case DRM_FORMAT_ARGB8888:
> +	case DRM_FORMAT_XBGR8888:
> +	case DRM_FORMAT_ABGR8888:
> +	case DRM_FORMAT_XRGB2101010:
> +	case DRM_FORMAT_ARGB2101010:
> +	case DRM_FORMAT_ABGR2101010:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +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
> 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 v2 2/3] drm/log: avoid WARN when searching for usable format

[Jocelyn Falempe]

On 14/10/2025 22:08, Francesco Valla wrote:
> 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.

Thanks, it looks good to me.

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

> 
> 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;
>   }
> 

Re: [PATCH v2 3/3] drm/panic: avoid WARN when checking format support

[Jocelyn Falempe]

On 14/10/2025 22:08, Francesco Valla wrote:
> 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.
> 

Thanks, it looks good to me.

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

> 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)
>