[PATCH 3/5] fbdev: Introduce devm_register_framebuffer()

[Helge Deller]

On 8/30/24 10:25, Bert Karwatzki wrote:
> 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 at weissschuh.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!

Good.

Thomas, please just resend the fixed patch #3 (this one).
And maybe you want to document devm_unregister_framebuffer()
similiar to what you added for devm_register_framebuffer() ?

Helge