linux-kernel - Re: [PATCH] ACPI / button: remove pointer to old lid

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Date:	Fri, 29 Jul 2016 09:53:35 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:	"Zheng, Lv" <lv.zheng@...el.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / button: remove pointer to old lid_sysfs on unbind

On Jul 29 2016 or thereabouts, Zheng, Lv wrote:
> Hi, Benjamin
> 
> > From: linux-acpi-owner@...r.kernel.org [mailto:linux-acpi-
> > owner@...r.kernel.org] On Behalf Of Benjamin Tissoires
> > Subject: [PATCH] ACPI / button: remove pointer to old lid_sysfs on unbind
> > 
> > When we removed the procfs dir on error or if the driver is
> > unbound, the two variables acpi_lid_dir and acpi_button_dir
> > were not reset. On the next rebind, those static variables
> > were not null and we couldn't re-register the device again.
> > 
> > Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
> > ---
> >  drivers/acpi/button.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
> > index 5c3b091..e413599 100644
> > --- a/drivers/acpi/button.c
> > +++ b/drivers/acpi/button.c
> > @@ -188,9 +188,11 @@ done:
> [Lv Zheng] 
> I have a concern here for acpi_button_add_fs().
> It looks like that this function doesn't support 2 lid devices.
> So why do we need /proc/acpi/button/lid/LID0 folder?

History I guess?

- (re)introduced in b34a803 "[ACPI] restore /proc/acpi/button/ (ala 2.6.12)"
  (2005-08-03)
- procfs cleaned up in 912b742 "ACPI button: remove unused procfs I/F"
  (2011-03-23)

And I would believe given that it was introduced prior 2.6.12, it's now
kernel ABI.

> 
> >  remove_dev_dir:
> >  	remove_proc_entry(acpi_device_bid(device),
> >  			  acpi_lid_dir);
> > +	acpi_lid_dir = NULL;
> >  	acpi_device_dir(device) = NULL;
> >  remove_lid_dir:
> >  	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID,
> > acpi_button_dir);
> [Lv Zheng] 
> Should acpi_lid_dir = NULL be put here?

Right

> 
> > +	acpi_button_dir = NULL;
> >  remove_button_dir:
> >  	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
> [Lv Zheng] 
> Should acpi_button_dir = NULL be put here?
> 

Right

> >  	goto done;
> > @@ -207,8 +209,10 @@ static int acpi_button_remove_fs(struct
> > acpi_device *device)
> >  			  acpi_device_dir(device));
> >  	remove_proc_entry(acpi_device_bid(device),
> >  			  acpi_lid_dir);
> > +	acpi_lid_dir = NULL;
> >  	acpi_device_dir(device) = NULL;
> >  	remove_proc_entry(ACPI_BUTTON_SUBCLASS_LID,
> > acpi_button_dir);
> [Lv Zheng] 
> Should acpi_lid_dir = NULL be put here?
> 
> > +	acpi_button_dir = NULL;
> >  	remove_proc_entry(ACPI_BUTTON_CLASS, acpi_root_dir);
> [Lv Zheng] 
> Should acpi_button_dir = NULL be put here?

Right for these too to, but it won't change the result in the end :)

I'll send a v2 ASAP.

Cheers,
Benjamin

> 
> Thanks and best regards
> Lv
> 
> > 
> >  	return 0;
> > --
> > 2.5.5
> > 
> > --
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