linux-kernel - Re: [PATCH v2] hisi_lpc: Use acpi_dev_for_each

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Date:   Thu, 30 Jun 2022 14:37:14 +0100
From:   John Garry <john.garry@...wei.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
CC:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] hisi_lpc: Use acpi_dev_for_each_child()

On 30/06/2022 13:48, Rafael J. Wysocki wrote:
> On Wed, Jun 29, 2022 at 3:47 PM Rafael J. Wysocki <rjw@...ysocki.net> 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).
> 
> I've overlooked another usage of the children list in hisi_lpc, in
> hisi_lpc_acpi_probe(), and eliminating that one is a bit more
> complicated.
> 
> So please scratch this one and I will send a v3 when 0-day tells me
> that it builds.

Hi Rafael,

If it makes things simpler then I can just fix the driver so that we 
can't unload it. Let me know if that suits better.

Cheers

> 
>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>> Acked-by: John Garry <john.garry@...wei.com>
>> ---
>>
>> -> v2:
>>     * Drop unused local variable (John).
>>     * Add ACK from John.
>>
>> ---
>>   drivers/bus/hisi_lpc.c |   14 ++++++++------
>>   1 file changed, 8 insertions(+), 6 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 +486,9 @@ 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;
>> -
>>          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);
>>   }
>>
>>   /*
>>
>>
>>
> .