Re: [RFC v3 08/12] drm/framebuffer: Add drm_mode_can_dirtyfb()

From: Daniel Vetter <daniel@ffwll.ch>
To: "Noralf Trønnes" <noralf@tronnes.org>
Cc: daniel.vetter@ffwll.ch, intel-gfx@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org,
	laurent.pinchart@ideasonboard.com
Subject: Re: [RFC v3 08/12] drm/framebuffer: Add drm_mode_can_dirtyfb()
Date: Tue, 6 Mar 2018 09:45:20 +0100	[thread overview]
Message-ID: <20180306084520.GG22212@phenom.ffwll.local> (raw)
In-Reply-To: <20180222200653.19453-9-noralf@tronnes.org>

On Thu, Feb 22, 2018 at 09:06:49PM +0100, Noralf Trønnes wrote:
> Add a function so the generic fbdev client can check if the framebuffer
> does flushing. This is needed to set up deferred I/O.
> 
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

Again I guess not needed if we use drm_framebuffer * internally for
in-kernel clients.

For a high-level design I think the only place where we have to use the
abstract (drm_file, id) pair is for backing storage buffers, because not
every driver is using drm_gem_object for that. But otherwise I don't think
there's a need, and not using the abstract IDs makes for more cumbersome
code I think. Real userspace compositors also recreate their own mirroring
objects as the first thing, since the IDs are all a bit unwiedling to
manage.
-Daniel

> ---
>  drivers/gpu/drm/drm_framebuffer.c | 31 +++++++++++++++++++++++++++++++
>  include/drm/drm_framebuffer.h     |  2 ++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index ad8f7d308656..a659cff45844 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -600,6 +600,37 @@ int drm_mode_dirtyfb_ioctl(struct drm_device *dev,
>  	return drm_mode_dirtyfb(dev, data, file_priv, true);
>  }
>  
> +/**
> + * drm_mode_can_dirtyfb - check if the FB does flushing
> + * @dev: drm device
> + * @fb_id: Framebuffer id
> + * @file_priv: drm file
> + *
> + * Returns:
> + * True if the framebuffer does flushing, false otherwise.
> + */
> +bool drm_mode_can_dirtyfb(struct drm_device *dev, u32 fb_id,
> +			  struct drm_file *file_priv)
> +{
> +	struct drm_framebuffer *fb;
> +	bool ret = false;
> +
> +	if (!drm_core_check_feature(dev, DRIVER_MODESET))
> +		return false;
> +
> +	fb = drm_framebuffer_lookup(dev, file_priv, fb_id);
> +	if (!fb)
> +		return false;
> +
> +	if (fb->funcs->dirty)
> +		ret = true;
> +
> +	drm_framebuffer_put(fb);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_mode_can_dirtyfb);
> +
>  /**
>   * drm_fb_release - remove and free the FBs on this file
>   * @priv: drm file for the ioctl
> diff --git a/include/drm/drm_framebuffer.h b/include/drm/drm_framebuffer.h
> index c50502c656e5..05d170f4e215 100644
> --- a/include/drm/drm_framebuffer.h
> +++ b/include/drm/drm_framebuffer.h
> @@ -216,6 +216,8 @@ struct drm_framebuffer *drm_framebuffer_lookup(struct drm_device *dev,
>  void drm_framebuffer_remove(struct drm_framebuffer *fb);
>  void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
>  void drm_framebuffer_unregister_private(struct drm_framebuffer *fb);
> +bool drm_mode_can_dirtyfb(struct drm_device *dev, u32 fb_id,
> +			  struct drm_file *file_priv);
>  
>  /**
>   * drm_framebuffer_get - acquire a framebuffer reference
> -- 
> 2.15.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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