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Message-ID: <b026d815-dd6e-48a6-8efa-4631ed7cca9c@redhat.com>
Date: Mon, 6 Oct 2025 10:06:51 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Jani Nikula <jani.nikula@...ux.intel.com>,
Francesco Valla <francesco@...la.it>,
Javier Martinez Canillas <javierm@...hat.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/draw: add drm_draw_can_convert_from_xrgb8888
On 10/6/25 08:48, Jani Nikula wrote:
> On Sun, 05 Oct 2025, Francesco Valla <francesco@...la.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@...la.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,
>
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