linux-kernel - Re: [PATCH] ACPI / scan: Allow ACPI drivers to bind to PNP device objects

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Date:	Sun, 24 Aug 2014 15:06:50 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Dirk Griesbach <spamthis@...enet.de>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: [PATCH] ACPI / scan: Allow ACPI drivers to bind to PNP device
 objects

On Thu, 2014-08-21 at 06:04 +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> We generally don't allow ACPI drivers to bind to ACPI device objects
> that companion "physical" device objects are created for to avoid
> situations in which two different drivers may attempt to handle one
> device at the same time.  Recent ACPI device enumeration rework
> extended that approach to ACPI PNP devices by starting to use a scan
> handler for enumerating them.  However, we previously allowed ACPI
> drivers to bind to ACPI device objects with existing PNP device
> companions and changing that led to functional regressions on some
> systems.
> 
> For this reason, add a special check for PNP devices in
> acpi_device_probe() so that ACPI drivers can bind to ACPI device
> objects having existing PNP device companions as before.
> 
> Fixes: eec15edbb0e1 (ACPI / PNP: use device ID list for PNPACPI device enumeration)
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=81511
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=81971
> Reported-and-tested-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
> Reported-and-tested-by: Dirk Griesbach <spamthis@...enet.de>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/acpi/acpi_pnp.c |    5 +++++
>  drivers/acpi/internal.h |    1 +
>  drivers/acpi/scan.c     |    2 +-
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> Index: linux-pm/drivers/acpi/acpi_pnp.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/acpi_pnp.c
> +++ linux-pm/drivers/acpi/acpi_pnp.c
> @@ -396,3 +396,8 @@ void __init acpi_pnp_init(void)
>  {
>  	acpi_scan_add_handler(&acpi_pnp_handler);
>  }
> +
> +bool is_acpi_pnp_device(struct acpi_device *adev)
> +{
> +	return adev->handler == &acpi_pnp_handler;
> +}

can we reuse acpi_is_pnp_device()?
The only difference is that acpi_is_pnp_device() returns true for
RTC_CMOS devices, which is not a problem IMO because RTC CMOS devices
have PNP driver only.

thanks,
rui

> Index: linux-pm/drivers/acpi/internal.h
> ===================================================================
> --- linux-pm.orig/drivers/acpi/internal.h
> +++ linux-pm/drivers/acpi/internal.h
> @@ -86,6 +86,7 @@ void acpi_device_add_finalize(struct acp
>  void acpi_free_pnp_ids(struct acpi_device_pnp *pnp);
>  bool acpi_device_is_present(struct acpi_device *adev);
>  bool acpi_device_is_battery(struct acpi_device *adev);
> +bool is_acpi_pnp_device(struct acpi_device *adev);
>  
>  /* --------------------------------------------------------------------------
>                                    Power Resource
> Index: linux-pm/drivers/acpi/scan.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/scan.c
> +++ linux-pm/drivers/acpi/scan.c
> @@ -975,7 +975,7 @@ static int acpi_device_probe(struct devi
>  	struct acpi_driver *acpi_drv = to_acpi_driver(dev->driver);
>  	int ret;
>  
> -	if (acpi_dev->handler)
> +	if (acpi_dev->handler && !is_acpi_pnp_device(acpi_dev))
>  		return -EINVAL;
>  
>  	if (!acpi_drv->ops.add)


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