linux-kernel - Re: [PATCH] ACPI / scan: Simplify ACPI driver probing

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Date:	Mon, 10 Jun 2013 22:01:47 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Aaron Lu <aaron.lu@...el.com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI / scan: Simplify ACPI driver probing

On Monday, June 10, 2013 09:28:58 PM Aaron Lu wrote:
> On 06/10/2013 06:16 AM, Rafael J. Wysocki wrote:
> > On Sunday, June 09, 2013 09:54:49 AM Aaron Lu wrote:
> >> On 06/09/2013 09:19 AM, Aaron Lu wrote:
> >>> On 06/09/2013 06:28 AM, Rafael J. Wysocki wrote:
> >>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>>>
> >>>> There is no particular reason why acpi_bus_driver_init() needs to be
> >>>> a separate function and its location with respect to its only caller,
> >>>> acpi_device_probe(), makes the code a bit difficult to follow.
> >>>>
> >>>> Besides, it doesn't really make sense to check if 'device' is not
> >>>> NULL in acpi_bus_driver_init(), because we've already dereferenced
> >>>> dev->driver in acpi_device_probe() at that point, so that check has
> >>>> to be moved to acpi_device_probe() anyway.
> >>>>
> >>>> For these reasons, drop acpi_bus_driver_init() altogether and move
> >>>> the code from it directly into acpi_device_probe().
> >>>>
> >>>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >>>> ---
> >>>>
> >>>> Should apply on top of the bleeding-edge branch of the linux-pm.git tree.
> >>>>
> >>>> Thanks,
> >>>> Rafael
> >>>>
> >>>> ---
> >>>>  drivers/acpi/scan.c |   88 +++++++++++++++++++---------------------------------
> >>>>  1 file changed, 33 insertions(+), 55 deletions(-)
> >>>>
> >>>> Index: linux-pm/drivers/acpi/scan.c
> >>>> ===================================================================
> >>>> --- linux-pm.orig/drivers/acpi/scan.c
> >>>> +++ linux-pm/drivers/acpi/scan.c
> >>>> @@ -933,32 +933,45 @@ static void acpi_device_remove_notify_ha
> >>>>  					   acpi_device_notify);
> >>>>  }
> >>>>  
> >>>> -static int acpi_bus_driver_init(struct acpi_device *, struct acpi_driver *);
> >>>>  static int acpi_device_probe(struct device * dev)
> >>>>  {
> >>>> -	struct acpi_device *acpi_dev = to_acpi_device(dev);
> >>>> -	struct acpi_driver *acpi_drv = to_acpi_driver(dev->driver);
> >>>> +	struct acpi_device *acpi_dev;
> >>>> +	struct acpi_driver *acpi_drv;
> >>>>  	int ret;
> >>>>  
> >>>> -	ret = acpi_bus_driver_init(acpi_dev, acpi_drv);
> >>>> -	if (!ret) {
> >>>> -		if (acpi_drv->ops.notify) {
> >>>> -			ret = acpi_device_install_notify_handler(acpi_dev);
> >>>> -			if (ret) {
> >>>> -				if (acpi_drv->ops.remove)
> >>>> -					acpi_drv->ops.remove(acpi_dev);
> >>>> -				acpi_dev->driver = NULL;
> >>>> -				acpi_dev->driver_data = NULL;
> >>>> -				return ret;
> >>>> -			}
> >>>> -		}
> >>>> +	if (!dev || !dev->driver)
> >>>> +		return -EINVAL;
> >>>
> >>> Just out of curiosity, will dev ever be NULL in this function?
> >>> This function is called in really_probe by dev->bus->probe after
> >>> assigning dev->driver, so does the above check make any sense?
> > 
> > Well, it makes sense as such, but it's not useful. :-)
> > 
> >> BTW, I also tested the patch on a desktop and two laptops, no problems
> >> found. Feel free to add my tested-by tag.
> > 
> > I've modified the patch to remove that check and will post it again shortly.
> > Can you please give the new version a run?
> 
> Actually, I added:
> dev_info(dev, "%s: driver=%s\n", __func__, dev->driver->name);
> before the if (!dev || !dev->driver) check while doing the tests to
> verify my thoughts, so your new patch should also be fine on those
> test systems, and my tested-by should still qualify.
> 
> It's national holiday here (6/10-6/12), but if you want to be sure, I
> can do the tests on 6/13 when getting back to work.

That won't hurt, but it's 3.11 material anyway, so it's going to get some
testing (hopefully).

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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