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Date:   Wed, 17 Apr 2019 13:01:19 +0200
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc:     Daniel Vetter <daniel.vetter@intel.com>,
        David Airlie <airlied@linux.ie>,
        Sean Paul <seanpaul@chromium.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org,
        Emil Velikov <emil.velikov@collabora.com>
Subject: Re: [PATCH 04/20] drm/fourcc: Pass the format_info pointer to
 drm_format_plane_width/height
Message-ID: <20190417110119.ygp6h7kpzzo5a27l@flea>
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On Wed, Apr 17, 2019 at 12:47:48PM +0200, Maarten Lankhorst wrote:
> > +/**
> > + * drm_format_info_plane_width - width of the plane given the first plane
> > + * @format: pixel format info
> > + * @width: width of the first plane
> > + * @plane: plane index
> > + *
> > + * Returns:
> > + * The width of @plane, given that the width of the first plane is @width.
> > + */
> > +static inline
> > +int drm_format_info_plane_width(const struct drm_format_info *info, int width,
> > +				int plane)
> > +{
> > +	if (!info || plane >= info->num_planes)
> > +		return 0;
> > +
> > +	if (plane == 0)
> > +		return width;
> > +
> > +	return width / info->hsub;
> > +}
> > +
> > +/**
> > + * drm_format_info_plane_height - height of the plane given the first plane
> > + * @format: pixel format info
> > + * @height: height of the first plane
> > + * @plane: plane index
> > + *
> > + * Returns:
> > + * The height of @plane, given that the height of the first plane is @height.
> > + */
> > +static inline
> > +int drm_format_info_plane_height(const struct drm_format_info *info, int height,
> > +				 int plane)
> > +{
> > +	if (!info || plane >= info->num_planes)
> > +		return 0;
> > +
> > +	if (plane == 0)
> > +		return height;
> > +
> > +	return height / info->vsub;
> > +}
>
> Why the null checks? None of the other inlines for drm_format_info
> perform them.

Unless I'm mistaken, the subsampling only applies to the planes with
the chrominance, which are always >= 1. Therefore the plane 0 is
always the luminance, to which the subsampling doesn't apply.

Or are you talking about something else?

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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