linux-kernel - Re: [PATCH 4/7] platform/x86: hp-bioscfg: Use wmi_instance

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Message-ID: <cbea0f2a-a66f-4ed8-9b19-6010b188f69f@gmx.de>
Date: Tue, 4 Feb 2025 14:06:20 +0100
From: Armin Wolf <W_Armin@....de>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: james@...iv.tech, markpearson@...ovo.com, jorge.lopez2@...com,
 jdelvare@...e.com, linux@...ck-us.net, linux-hwmon@...r.kernel.org,
 LKML <linux-kernel@...r.kernel.org>, Hans de Goede <hdegoede@...hat.com>,
 platform-driver-x86@...r.kernel.org, corbet@....net,
 linux-doc@...r.kernel.org
Subject: Re: [PATCH 4/7] platform/x86: hp-bioscfg: Use wmi_instance_count()

Am 04.02.25 um 11:37 schrieb Ilpo Järvinen:

> On Mon, 3 Feb 2025, Armin Wolf wrote:
>
>> The WMI core already knows the instance count of a WMI guid.
>> Use this information instead of querying all possible instances
>> which is slow and might be unreliable.
>>
>> Signed-off-by: Armin Wolf <W_Armin@....de>
>> ---
>>   drivers/platform/x86/hp/hp-bioscfg/bioscfg.c | 13 +++++--------
>>   1 file changed, 5 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/platform/x86/hp/hp-bioscfg/bioscfg.c b/drivers/platform/x86/hp/hp-bioscfg/bioscfg.c
>> index 0b277b7e37dd..63c78b4d8258 100644
>> --- a/drivers/platform/x86/hp/hp-bioscfg/bioscfg.c
>> +++ b/drivers/platform/x86/hp/hp-bioscfg/bioscfg.c
>> @@ -388,16 +388,13 @@ union acpi_object *hp_get_wmiobj_pointer(int instance_id, const char *guid_strin
>>    */
>>   int hp_get_instance_count(const char *guid_string)
>>   {
>> -	union acpi_object *wmi_obj = NULL;
>> -	int i = 0;
>> +	int ret;
>>
>> -	do {
>> -		kfree(wmi_obj);
>> -		wmi_obj = hp_get_wmiobj_pointer(i, guid_string);
>> -		i++;
>> -	} while (wmi_obj);
>> +	ret = wmi_instance_count(guid_string);
>> +	if (ret < 0)
>> +		return 0;
>>
>> -	return i - 1;
>> +	return ret;
>>   }
> Hi Armin,
>
> While it is the existing way of doing things, I don't like how the error
> is not properly passed on here. And if the error handling is pushed
> upwards to the calling sites, then this entire function becomes useless
> and wmi_instance_count() could be used directly in the callers.
>
The thing is that for the hp-bioscfg driver, a missing WMI GUID is not an error.
In this case 0 instances are available.

I would keep this function for now.

Thanks,
Armin Wolf