linux-kernel - Re: [PATCH 3/5] fbdev: Introduce devm_register

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Message-ID: <7fec4df2e44ea2b11ac617d1a4ed5cbb49214f7b.camel@web.de>
Date: Fri, 30 Aug 2024 10:25:37 +0200
From: Bert Karwatzki <spasswolf@....de>
To: Thomas Weißschuh <linux@...ssschuh.net>, Helge Deller
	 <deller@....de>
Cc: linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>, Peter Jones
	 <pjones@...hat.com>, spasswolf@....de
Subject: Re: [PATCH 3/5] fbdev: Introduce devm_register_framebuffer()

Am Freitag, dem 30.08.2024 um 09:17 +0200 schrieb Thomas Weißschuh:
> Hi everybody,
>
> On 2024-08-27 17:25:14+0000, Thomas Weißschuh wrote:
> > Introduce a device-managed variant of register_framebuffer() which
> > automatically unregisters the framebuffer on device destruction.
> > This can simplify the error handling and resource management in drivers.
>
> Bert reported that this series broke his framebuffer ([0], [1]).
>
> [0] https://lore.kernel.org/lkml/20240829224124.2978-1-spasswolf@web.de/
> [1] https://lore.kernel.org/lkml/20240829230438.3226-1-spasswolf@web.de/
>
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > ---
> >  drivers/video/fbdev/core/fbmem.c | 24 ++++++++++++++++++++++++
> >  include/linux/fb.h               |  1 +
> >  2 files changed, 25 insertions(+)
> >
> > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> > index 4c4ad0a86a50..d17a2daa2483 100644
> > --- a/drivers/video/fbdev/core/fbmem.c
> > +++ b/drivers/video/fbdev/core/fbmem.c
> > @@ -544,6 +544,30 @@ unregister_framebuffer(struct fb_info *fb_info)
>
> [..]
>
> > +/**
> > + *	devm_register_framebuffer - resource-managed frame buffer device registration
> > + *	@dev: device the framebuffer belongs to
> > + *	@fb_info: frame buffer info structure
> > + *
> > + *	Registers a frame buffer device @fb_info to device @dev.
> > + *
> > + *	Returns negative errno on error, or zero for success.
> > + *
> > + */
> > +int
> > +devm_register_framebuffer(struct device *dev, struct fb_info *fb_info)
> > +{
> > +	return devm_add_action_or_reset(dev, devm_unregister_framebuffer, fb_info);
> > +}
> > +EXPORT_SYMBOL(devm_register_framebuffer);
>
> This implementation is wrong, it never actually registers the
> framebuffer. It should look like this:
>
> int
> devm_register_framebuffer(struct device *dev, struct fb_info *fb_info)
> {
> 	int ret;
>
> 	ret = register_framebuffer(fb_info);
> 	if (ret)
> 		return ret;
>
> 	return devm_add_action_or_reset(dev, devm_unregister_framebuffer, fb_info);
> }
> EXPORT_SYMBOL(devm_register_framebuffer);
>
> Bert, could you test this?
> Helge, do you want me to resend the series, minus the original patch 1?

Yes, this works for me. Thanks!

Bert Karwatzki