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

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Message-ID: <Zp5o6fnBuTlxm-X_@phenom.ffwll.local>
Date: Mon, 22 Jul 2024 16:12:57 +0200
From: Daniel Vetter <daniel.vetter@...ll.ch>
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>, 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()

On Thu, Jul 18, 2024 at 11:30:05AM +0200, Jocelyn Falempe wrote:
> 
> 
> On 18/07/2024 09:04, Jocelyn Falempe wrote:
> > 
> > 
> > On 17/07/2024 17:08, Daniel Vetter wrote:
> > > 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);
> > > 
> > > This feels like overkill since you currently only have one user in the
> > > fbdev emulation code, but maybe useful in some other places ...
> > > 
> > > > +
> > > >   /**
> > > >    * 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);
> > > 
> > > Since it's internal only, this should be in
> > > drivers/gpu/drm/drm_crtc_internal.h and not int he include for drivers.
> > 
> > Yes, that makes sense, drivers won't need that API.
> > 
> > > With that:
> > > 
> > > Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> > > 
> > > >   void drm_panic_register(struct drm_device *dev);
> > > >   void drm_panic_unregister(struct drm_device *dev);
> > > 
> > > These two are only used in drm.ko. Can you please move them to
> > > drm_crtc_internal.h too and drop the EXPORT_SYMBOL in a follow-up patch?
> > > We're trying to limit the exported interface and official headers to
> > > really only the pieces drivers actually need.
> > 
> > Sure, I'll add this to my next drm_panic series.
> 
> I think this also applies to drm_panic_init() and drm_panic_exit(), that I
> introduce in my QR code series:
> https://patchwork.freedesktop.org/patch/604890/?series=135944&rev=2
> I will move them to drm_crtc_internal.h

Yup.
-Sima

> 
> > 
> > > 
> > > Thanks, Sima
> > > 
> > > >   #else
> > > > +bool drm_panic_is_enabled(struct drm_device *dev) {return false; }
> > > >   static inline void drm_panic_register(struct drm_device *dev) {}
> > > >   static inline void drm_panic_unregister(struct drm_device *dev) {}
> > > > -- 
> > > > 2.45.2
> > > > 
> > > 
> > 
> > Best regards,
> > 
> 

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