linux-kernel - Re: [PATCH] hisi_lpc: Use acpi_dev_for_each

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Date:   Wed, 29 Jun 2022 14:33:54 +0100
From:   John Garry <john.garry@...wei.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>
CC:     LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] hisi_lpc: Use acpi_dev_for_each_child()

On 29/06/2022 13:55, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Instead of walking the list of children of an ACPI device directly,
> use acpi_dev_for_each_child() to carry out an action for all of
> the given ACPI device's children.
> 
> This will help to eliminate the children list head from struct
> acpi_device as it is redundant and it is used in questionable ways
> in some places (in particular, locking is needed for walking the
> list pointed to it safely, but it is often missing).
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Hi Rafael,

> ---
>   drivers/bus/hisi_lpc.c |   12 ++++++++----
>   1 file changed, 8 insertions(+), 4 deletions(-)
> 
> Index: linux-pm/drivers/bus/hisi_lpc.c
> ===================================================================
> --- linux-pm.orig/drivers/bus/hisi_lpc.c
> +++ linux-pm/drivers/bus/hisi_lpc.c
> @@ -471,6 +471,12 @@ static int hisi_lpc_acpi_remove_subdev(s
>   	return 0;
>   }
>   
> +static int hisi_lpc_acpi_clear_enumerated(struct acpi_device *adev, void *not_used)
> +{
> +	acpi_device_clear_enumerated(adev);
> +	return 0;
> +}
> +
>   struct hisi_lpc_acpi_cell {
>   	const char *hid;
>   	const char *name;
> @@ -480,13 +486,11 @@ struct hisi_lpc_acpi_cell {
>   
>   static void hisi_lpc_acpi_remove(struct device *hostdev)
>   {
> -	struct acpi_device *adev = ACPI_COMPANION(hostdev);
>   	struct acpi_device *child;
>   
I got this warn:

drivers/bus/hisi_lpc.c: In function ‘hisi_lpc_acpi_remove’:
drivers/bus/hisi_lpc.c:489:22: warning: unused variable ‘child’ 
[-Wunused-variable]
  489 |  struct acpi_device *child;
      |                      ^~~~~
  CC      drivers/bus/brcmstb_gisb.

With that fixed:

Acked-by: John Garry <john.garry@...wei.com>

Can you route this through one of your trees?

>   	device_for_each_child(hostdev, NULL, hisi_lpc_acpi_remove_subdev);
> -
> -	list_for_each_entry(child, &adev->children, node)
> -		acpi_device_clear_enumerated(child);
> +	acpi_dev_for_each_child(ACPI_COMPANION(hostdev),
> +				hisi_lpc_acpi_clear_enumerated, NULL);
>   }
>   
>   /*
> 
> 
> 

BTW, I don't know why I ever added a remove method for this driver 
instead of just setting suppress_bind_attrs....

Thanks,
John