linux-kernel - Re: [PATCH 2/2] hwmon: (dell-smm) Unify i8k_ioctl() and i8k_ioctl

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Date:   Mon, 22 Nov 2021 19:50:14 +0100
From:   Armin Wolf <W_Armin@....de>
To:     Guenter Roeck <linux@...ck-us.net>,
        Pali Rohár <pali@...nel.org>
Cc:     jdelvare@...e.com, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: (dell-smm) Unify i8k_ioctl() and
 i8k_ioctl_unlocked()


Am 22.11.21 um 18:55 schrieb Guenter Roeck:
> On 11/22/21 8:01 AM, Pali Rohár wrote:
>> On Saturday 20 November 2021 18:03:19 Armin Wolf wrote:
>>> The only purpose of i8k_ioctl() is to call i8k_ioctl_unlocked()
>>> with i8k_mutex held. Judging from the hwmon code, this mutex
>>> only needs to be held when setting the fan speed/mode.
>>
>> Really? I think that there is no difference between setting and getting
>> fan speed/mode. At least I do not see why 'set' needs mutex and 'get' do
>> not need it. Some more explanation is needed...
>>
> I8K_SET_FAN sets the fan speed and returns the current status. Without
> locking, the returned status may not match or be associated with the
> previous
> set operation.
>
> Maybe that doesn't matter, and the synchronization is not needed. If so,
> you can probably remove the locking entirely.
>
> Guenter

That is the reason i kept the locking code. Since i do not want to break
the ioctl interfacein any way, removing the locking code seems too risky
to me.

Armin