linux-kernel - Re: [PATCH 1/3] drm/panic: Add drm_panic_is

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Message-ID: <Zpo9Xv6wLevidsNa@ideak-desk.fi.intel.com>
Date: Fri, 19 Jul 2024 13:18:06 +0300
From: Imre Deak <imre.deak@...el.com>
To: Jocelyn Falempe <jfalempe@...hat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Helge Deller <deller@....de>,
	"Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Javier Martinez Canillas <javierm@...hat.com>,
	Samuel Thibault <samuel.thibault@...-lyon.org>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/panic: Add drm_panic_is_enabled()

Hi,

On Wed, Jul 17, 2024 at 10:48:39AM +0200, Jocelyn Falempe wrote:
> It allows to check if the drm device supports drm_panic.
> Prepare the work to have better integration with fbcon and vtconsole.
> 
> Signed-off-by: Jocelyn Falempe <jfalempe@...hat.com>
> ---
>  drivers/gpu/drm/drm_panic.c | 20 ++++++++++++++++++++
>  include/drm/drm_panic.h     |  2 ++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
> index 948aed00595e..d9a25c2d0a65 100644
> --- a/drivers/gpu/drm/drm_panic.c
> +++ b/drivers/gpu/drm/drm_panic.c
> @@ -703,6 +703,26 @@ static void debugfs_register_plane(struct drm_plane *plane, int index)
>  static void debugfs_register_plane(struct drm_plane *plane, int index) {}
>  #endif /* CONFIG_DRM_PANIC_DEBUG */
>  
> +/**
> + * drm_panic_is_enabled
> + * @dev: the drm device that may supports drm_panic
> + *
> + * returns true if the drm device supports drm_panic
> + */
> +bool drm_panic_is_enabled(struct drm_device *dev)
> +{
> +	struct drm_plane *plane;
> +
> +	if (!dev->mode_config.num_total_plane)
> +		return false;
> +
> +	drm_for_each_plane(plane, dev)
> +		if (plane->helper_private && plane->helper_private->get_scanout_buffer)
> +			return true;
> +	return false;
> +}
> +EXPORT_SYMBOL(drm_panic_is_enabled);
> +
>  /**
>   * drm_panic_register() - Initialize DRM panic for a device
>   * @dev: the drm device on which the panic screen will be displayed.
> diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
> index 73bb3f3d9ed9..c3a358dc3e27 100644
> --- a/include/drm/drm_panic.h
> +++ b/include/drm/drm_panic.h
> @@ -148,11 +148,13 @@ struct drm_scanout_buffer {
>  
>  #ifdef CONFIG_DRM_PANIC
>  
> +bool drm_panic_is_enabled(struct drm_device *dev);
>  void drm_panic_register(struct drm_device *dev);
>  void drm_panic_unregister(struct drm_device *dev);
>  
>  #else
>  
> +bool drm_panic_is_enabled(struct drm_device *dev) {return false; }

This was moved to drivers/gpu/drm/drm_crtc_internal.h in the applied
version and I can't find that version on the mailing list; imo this kind
of change requires a resend.

Also, the above breaks CONFIG_DRM_PANIC=n builds:

In file included from drivers/gpu/drm/drm_atomic_uapi.c:43:
drivers/gpu/drm/drm_crtc_internal.h:322:6: error: no previous prototype for ‘drm_panic_is_enabled’ [-Werror=missing-prototypes]
  322 | bool drm_panic_is_enabled(struct drm_device *dev) {return false; }

Stubs like the above must be an inline function.

>  static inline void drm_panic_register(struct drm_device *dev) {}
>  static inline void drm_panic_unregister(struct drm_device *dev) {}
>  
> -- 
> 2.45.2
>