Subject: Re: [PATCH 2/2] hwmon: (dell-smm) Unify i8k_ioctl() and
 i8k_ioctl_unlocked()
To:     Guenter Roeck <linux@roeck-us.net>,
        =?UTF-8?Q?Pali_Roh=c3=a1r?= <pali@kernel.org>
Cc:     jdelvare@suse.com, linux-hwmon@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20211120170319.72369-1-W_Armin@gmx.de>
 <20211120170319.72369-3-W_Armin@gmx.de>
 <20211122160122.gf6i3qj6dnwi6wla@pali>
 <c23caeab-dd27-4c95-2e25-9eb0ff7b33f6@roeck-us.net>
From:   Armin Wolf <W_Armin@gmx.de>
Message-ID: <e336f501-fe07-7b49-bc65-d6ca443491ca@gmx.de>
Date:   Mon, 22 Nov 2021 19:50:14 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.13.0
MIME-Version: 1.0
In-Reply-To: <c23caeab-dd27-4c95-2e25-9eb0ff7b33f6@roeck-us.net>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Content-Language: en-US
Precedence: bulk


Am 22.11.21 um 18:55 schrieb Guenter Roeck:
> On 11/22/21 8:01 AM, Pali Roh=C3=A1r 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' d=
o
>> 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