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Subject: Re: [PATCH v2 08/14] drm: remove include of drmP.h from
 bridge/dw_hdmi.h
To:     Sam Ravnborg <sam@ravnborg.org>, Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
        Sean Paul <sean@poorly.run>,
        David Lechner <david@lechnology.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Cc:     Archit Taneja <architt@codeaurora.org>,
        Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>,
        Fabio Estevam <fabio.estevam@nxp.com>,
        Neil Armstrong <narmstrong@baylibre.com>
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <f478a3bc-2218-6561-e37e-ea654bc3e558@samsung.com>
Date:   Mon, 31 Dec 2018 11:53:40 +0100
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        <20181230174838.32330-9-sam@ravnborg.org>
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On 30.12.2018 18:48, Sam Ravnborg wrote:
> drmP.h is an relic from the days when there was a single header file.
> To enable the removal of drmP.h from all users drop include
> of drmP.h from bridge/dw_hdmi.h.
>
> A few files relied on the file included in drmP.h - add explicit
> include statements or forward declarations to these files.
> Build tested with arm and x86.
>
> v2:
> - prefer forward declarations when possible (Laurent Pinchart)
> - sort include files (Laurent Pinchart)
>
> Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: Andrzej Hajda <a.hajda@samsung.com>
> Cc: David Airlie <airlied@linux.ie>
> Cc: Daniel Vetter <daniel@ffwll.ch>
> Cc: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
> Cc: Fabio Estevam <fabio.estevam@nxp.com>
> Cc: Neil Armstrong <narmstrong@baylibre.com>
> Cc: Maxime Ripard <maxime.ripard@bootlin.com>


One general comment below.


> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c | 4 ++++
>  drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c              | 1 +
>  include/drm/bridge/dw_hdmi.h                        | 6 ++++--
>  3 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> index 2228689d9a5e..5cbb71a866d5 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -5,6 +5,10 @@
>   * Copyright (c) 2017 Renesas Solutions Corp.
>   * Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
>   */
> +
> +#include <linux/dma-mapping.h>
> +#include <linux/module.h>
> +
>  #include <drm/bridge/dw_hdmi.h>
>  
>  #include <sound/hdmi-codec.h>
> diff --git a/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c b/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> index 75490a3e0a2a..790d499daa10 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> @@ -7,6 +7,7 @@
>   * Contact: Laurent Pinchart (laurent.pinchart@ideasonboard.com)
>   */
>  
> +#include <linux/mod_devicetable.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
>  
> diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
> index 9c56412bb2cf..9f93895dde88 100644
> --- a/include/drm/bridge/dw_hdmi.h
> +++ b/include/drm/bridge/dw_hdmi.h
> @@ -10,9 +10,11 @@
>  #ifndef __DW_HDMI__
>  #define __DW_HDMI__
>  
> -#include <drm/drmP.h>
> -
> +struct drm_connector;
> +struct drm_display_mode;
> +struct drm_encoder;
>  struct dw_hdmi;
> +struct platform_device;
>  
>  /**
>   * DOC: Supported input formats and encodings


I wonder if it wouldn't be better to create common file for forward
declarations. For example: include/drm/drm_forward.h which will contain
only forward declarations, this way we could avoid adding these
declarations in every file again and again. Since I have not seen such
practice in kernel I wonder if such approach has no serious drawbacks,
but for now I do not see any, except it looks like another incarnation
of drmP.h :)

Quick grep shows potential candidates for forward declarations:

$ git grep -Ph '^struct drm_\S+;$' include/ drivers/gpu/ | sort | uniq
-c | sort -n | tail
      7 struct drm_encoder;
      7 struct drm_gem_object;
      8 struct drm_printer;
      9 struct drm_connector;
      9 struct drm_framebuffer;
     13 struct drm_plane;
     14 struct drm_crtc;
     22 struct drm_i915_private;
     23 struct drm_file;

     47 struct drm_device;


Anyway:

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

 --
Regards
Andrzej