linux-kernel - Re: [RFC PATCH v3 1/3] acpi: Introduce prepare_remove operation in acpi_device

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Date:	Mon, 26 Nov 2012 17:10:21 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>
Cc:	linux-acpi@...r.kernel.org, isimatu.yasuaki@...fujitsu.com,
	wency@...fujitsu.com, rjw@...k.pl, lenb@...nel.org,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [RFC PATCH v3 1/3] acpi: Introduce prepare_remove operation in
 acpi_device_ops

On Fri, 2012-11-23 at 18:50 +0100, Vasilis Liaskovitis wrote:
> This function should be registered for devices that need to execute some
> non-acpi related action in order to be safely removed. If this function
> returns zero, the acpi core can continue with removing the device.
> 
> Make acpi_bus_remove call the device-specific prepare_remove callback before
> removing the device. If prepare_remove fails, the removal is aborted.
> 
> Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@...fitbricks.com>
> ---
>  drivers/acpi/scan.c     |    9 ++++++++-
>  include/acpi/acpi_bus.h |    2 ++
>  2 files changed, 10 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 8c4ac6d..e1c1d5d 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1380,10 +1380,16 @@ static int acpi_device_set_context(struct acpi_device *device)
>  
>  static int acpi_bus_remove(struct acpi_device *dev, int rmdevice)
>  {
> +	int ret = 0;
>  	if (!dev)
>  		return -EINVAL;
>  
>  	dev->removal_type = ACPI_BUS_REMOVAL_EJECT;
> +
> +	if (dev->driver && dev->driver->ops.prepare_remove)
> +		ret = dev->driver->ops.prepare_remove(dev);
> +	if (ret)
> +		return ret;

Hi Vasilis,

The above code should be like below. Then you do not need to initialize
ret, either.  Please also add some comments explaining about
prepare_remove can fail, but remove cannot.

	if (dev->driver && dev->driver->ops.prepare_remove) {
		ret = dev->driver->ops.prepare_remove(dev);
		if (ret)
			return ret;
	}

>  	device_release_driver(&dev->dev);
>  
>  	if (!rmdevice)
> @@ -1702,7 +1708,8 @@ int acpi_bus_trim(struct acpi_device *start, int rmdevice)
>  				err = acpi_bus_remove(child, rmdevice);
>  			else
>  				err = acpi_bus_remove(child, 1);
> -
> +			if (err)
> +				return err;
>  			continue;
>  		}
>  
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 7ced5dc..9d94a55 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -94,6 +94,7 @@ typedef int (*acpi_op_start) (struct acpi_device * device);
>  typedef int (*acpi_op_bind) (struct acpi_device * device);
>  typedef int (*acpi_op_unbind) (struct acpi_device * device);
>  typedef void (*acpi_op_notify) (struct acpi_device * device, u32 event);
> +typedef int (*acpi_op_prepare_remove) (struct acpi_device *device);
>  
>  struct acpi_bus_ops {
>  	u32 acpi_op_add:1;
> @@ -107,6 +108,7 @@ struct acpi_device_ops {
>  	acpi_op_bind bind;
>  	acpi_op_unbind unbind;
>  	acpi_op_notify notify;
> +	acpi_op_prepare_remove prepare_remove;

I'd prefer pre_remove, which indicates this interface is called before
remove.  prepare_remove sounds as if it only performs preparation, which
may be misleading.

BTW, Rafael mentioned we should avoid extending ACPI driver's
interface...  But I do not have other idea, either.


Thanks,
-Toshi



>  };
>  
>  #define ACPI_DRIVER_ALL_NOTIFY_EVENTS	0x1	/* system AND device events */


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