linux-kernel - Re: [PATCH] drm/tinydrm: Advertise that we can do only DRM_FORMAT_MOD

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Date:   Sat, 27 Oct 2018 18:21:46 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Eric Anholt <eric@...olt.net>, dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/tinydrm: Advertise that we can do only
 DRM_FORMAT_MOD_LINEAR.


Den 25.10.2018 18.26, skrev Eric Anholt:
> Without this, the xserver relies on what the 3D driver exposes and
> assumes that the display can handle it, and then the DRM driver
> happily tries to scan out a tiled format.
>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>   drivers/gpu/drm/drm_simple_kms_helper.c     | 8 ++++++++
>   drivers/gpu/drm/tinydrm/core/tinydrm-core.c | 1 +
>   drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c | 6 +++++-
>   3 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_simple_kms_helper.c b/drivers/gpu/drm/drm_simple_kms_helper.c
> index 51fa978f0d23..917812448d1b 100644
> --- a/drivers/gpu/drm/drm_simple_kms_helper.c
> +++ b/drivers/gpu/drm/drm_simple_kms_helper.c
> @@ -190,6 +190,13 @@ static void drm_simple_kms_plane_cleanup_fb(struct drm_plane *plane,
>   	pipe->funcs->cleanup_fb(pipe, state);
>   }
>   
> +static bool drm_simple_kms_format_mod_supported(struct drm_plane *plane,
> +						uint32_t format,
> +						uint64_t modifier)
> +{
> +	return modifier == DRM_FORMAT_MOD_LINEAR;
> +}
> +

I assume this also works for the other drivers that use this helper.
A quick look at the code seems to support this assumption.
Format modifiers is something I've never looked at before.

Acked-by: Noralf Trønnes <noralf@...nnes.org>

>   static const struct drm_plane_helper_funcs drm_simple_kms_plane_helper_funcs = {
>   	.prepare_fb = drm_simple_kms_plane_prepare_fb,
>   	.cleanup_fb = drm_simple_kms_plane_cleanup_fb,
> @@ -204,6 +211,7 @@ static const struct drm_plane_funcs drm_simple_kms_plane_funcs = {
>   	.reset			= drm_atomic_helper_plane_reset,
>   	.atomic_duplicate_state	= drm_atomic_helper_plane_duplicate_state,
>   	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
> +	.format_mod_supported   = drm_simple_kms_format_mod_supported,
>   };
>   
>   /**
> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-core.c b/drivers/gpu/drm/tinydrm/core/tinydrm-core.c
> index 255341ee4eb9..9af51d982a33 100644
> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-core.c
> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-core.c
> @@ -146,6 +146,7 @@ static int tinydrm_init(struct device *parent, struct tinydrm_device *tdev,
>   	drm->dev_private = tdev;
>   	drm_mode_config_init(drm);
>   	drm->mode_config.funcs = &tinydrm_mode_config_funcs;
> +	drm->mode_config.allow_fb_modifiers = true;
>   
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c b/drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c
> index 7e8e24d0b7a7..eacfc0ec8ff1 100644
> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c
> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c
> @@ -184,6 +184,10 @@ tinydrm_display_pipe_init(struct tinydrm_device *tdev,
>   	struct drm_display_mode mode_copy;
>   	struct drm_connector *connector;
>   	int ret;
> +	static const uint64_t modifiers[] = {
> +		DRM_FORMAT_MOD_LINEAR,
> +		DRM_FORMAT_MOD_INVALID
> +	};
>   
>   	drm_mode_copy(&mode_copy, mode);
>   	ret = tinydrm_rotate_mode(&mode_copy, rotation);
> @@ -202,6 +206,6 @@ tinydrm_display_pipe_init(struct tinydrm_device *tdev,
>   		return PTR_ERR(connector);
>   
>   	return drm_simple_display_pipe_init(drm, &tdev->pipe, funcs, formats,
> -					    format_count, NULL, connector);
> +					    format_count, modifiers, connector);
>   }
>   EXPORT_SYMBOL(tinydrm_display_pipe_init);