linux-kernel - Re: [PATCH] drm: Fix comment doc for format

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Message-ID: <20191002183011.GA29177@ravnborg.org>
Date:   Wed, 2 Oct 2019 20:30:11 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        linux-kernel@...r.kernel.org, Maxime Ripard <mripard@...nel.org>,
        kernel@...labora.com, Sean Paul <sean@...rly.run>
Subject: Re: [PATCH] drm: Fix comment doc for format_modifiers

Hi Andrzej

Always good to have clear documentation.

On Wed, Oct 02, 2019 at 05:43:49PM +0200, Andrzej Pietrasiewicz wrote:
> To human readers
> 
> "array of struct drm_format modifiers" is almost indistinguishable from
> "array of struct drm_format_modifiers", especially given that
> struct drm_format_modifier does exist.
> 
> And indeed the parameter passes an array of uint64_t rather than an array
> of structs, but the first words of the comment suggest that it passes
> an array of structs.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> ---
>  drivers/gpu/drm/drm_plane.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index d6ad60ab0d38..df05d8a0dd63 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -160,7 +160,7 @@ static int create_in_format_blob(struct drm_device *dev, struct drm_plane *plane
>   * @funcs: callbacks for the new plane
>   * @formats: array of supported formats (DRM_FORMAT\_\*)
>   * @format_count: number of elements in @formats
> - * @format_modifiers: array of struct drm_format modifiers terminated by
> + * @format_modifiers: array of modifiers of struct drm_format terminated by
>   *                    DRM_FORMAT_MOD_INVALID
@format_modifiers is an array of DRM_FORMAT_* which are defined as:

#define fourcc_code(a, b, c, d) ((__u32)(a) | ((__u32)(b) << 8) | \
                                 ((__u32)(c) << 16) | ((__u32)(d) << 24))


But the array is a u64[] like this:
static const u64 tegra20_modifiers[] = {
        DRM_FORMAT_MOD_LINEAR,
        DRM_FORMAT_MOD_NVIDIA_TEGRA_TILED,
        DRM_FORMAT_MOD_INVALID
};

So this is not struct drm_format.

Can you try to give it a shot more?

	Sam