From: Thomas Zimmermann <tzimmermann@suse•de>
To: Daniel Vetter <daniel@ffwll•ch>,
Javier Martinez Canillas <javierm@redhat•com>
Cc: devicetree@vger•kernel.org, linux-fbdev@vger•kernel.org,
sam@ravnborg•org, frowand.list@gmail•com, deller@gmx•de,
dri-devel@lists•freedesktop.org, robh+dt@kernel•org,
paulus@samba•org, linuxppc-dev@lists•ozlabs.org,
linux@roeck-us•net
Subject: Re: [PATCH 2/2] fbdev: Remove hot-unplug workaround for framebuffers without device
Date: Wed, 13 Apr 2022 20:09:00 +0200 [thread overview]
Message-ID: <9d4599d9-e094-e7dd-5b91-282c2679aae4@suse.de> (raw)
In-Reply-To: <Ylb0316ABOhOe1Rb@phenom.ffwll.local>
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Hi
Am 13.04.22 um 18:05 schrieb Daniel Vetter:
> On Wed, Apr 13, 2022 at 12:50:50PM +0200, Javier Martinez Canillas wrote:
>> On 4/13/22 11:24, Thomas Zimmermann wrote:
>>> A workaround makes fbdev hot-unplugging work for framebuffers without
>>> device. The only user for this feature was offb. As each OF framebuffer
>>> now has an associated platform device, the workaround is no longer
>>> needed. Remove it. Effectively reverts commit 0f525289ff0d ("fbdev: Fix
>>> unregistering of framebuffers without device").
>>>
>>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse•de>
>>> ---
>>> drivers/video/fbdev/core/fbmem.c | 9 +--------
>>> 1 file changed, 1 insertion(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
>>> index bc6ed750e915..bdd00d381bbc 100644
>>> --- a/drivers/video/fbdev/core/fbmem.c
>>> +++ b/drivers/video/fbdev/core/fbmem.c
>>> @@ -1579,14 +1579,7 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
>>> * If it's not a platform device, at least print a warning. A
>>> * fix would add code to remove the device from the system.
>>> */
>>> - if (!device) {
>>> - /* TODO: Represent each OF framebuffer as its own
>>> - * device in the device hierarchy. For now, offb
>>> - * doesn't have such a device, so unregister the
>>> - * framebuffer as before without warning.
>>> - */
>>> - do_unregister_framebuffer(registered_fb[i]);
>>
>> Maybe we could still keep this for a couple of releases but with a big
>> warning that's not supported in case there are out-of-tree drivers out
>> there that still do this ?
>>
>> Or at least a warning if the do_unregister_framebuffer() call is removed.
>
> Yeah dying while holding console_lock isn't fun, and not having a WARN_ON
> + bail-out code pretty much forces bug reporters to do a bisect here to
> give us something more than "machine dies at boot with no messages".
>
> I'd just outright keep the WARN_ON here for 1-2 years even to really make
> sure we got all the bug reports, since often these older machines only
> update onto LTS releases.
If that's what the consent is, I'll go with it.
I'm just not sure if we talk about the same problem. offb didn't have a
platform device, so we recently added this workaround with 'if
(!device)'. All the other fbdev drivers have a platform device; and
anything else that could fail is out-of-tree. We don't really care about
those AFAIK.
With offb converted, we could practically remove all of the checks here
and call platform_device_unregister() unconditionally.
Best regards
Thomas
>
> And it needs to be a WARN_ON + bail out since BUG_ON is as bad as just
> oopsing.
> -Daniel
>
>>
>> Regardless of what you chose to do, the patch looks good to me.
>>
>> Reviewed-by: Javier Martinez Canillas <javierm@redhat•com>
>>
>> --
>> Best regards,
>>
>> Javier Martinez Canillas
>> Linux Engineering
>> Red Hat
>>
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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next prev parent reply other threads:[~2022-04-13 18:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-13 9:24 [PATCH 0/2] of: Register platform device for each framebuffer Thomas Zimmermann
2022-04-13 9:24 ` [PATCH 1/2] of: Create platform devices for OF framebuffers Thomas Zimmermann
2022-04-13 10:45 ` Javier Martinez Canillas
2022-04-13 10:49 ` Thomas Zimmermann
2022-04-13 12:51 ` Rob Herring
2022-04-13 17:58 ` Thomas Zimmermann
2022-04-13 18:02 ` Javier Martinez Canillas
2022-04-13 18:46 ` Rob Herring
2022-04-13 18:53 ` Rob Herring
2022-04-18 18:09 ` Thomas Zimmermann
2022-04-13 9:24 ` [PATCH 2/2] fbdev: Remove hot-unplug workaround for framebuffers without device Thomas Zimmermann
2022-04-13 10:50 ` Javier Martinez Canillas
2022-04-13 16:05 ` Daniel Vetter
2022-04-13 18:09 ` Thomas Zimmermann [this message]
2022-04-19 7:22 ` Javier Martinez Canillas
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