linux-kernel - Re: [PATCH v3] i8k: Autodetect maximal fan speed and fan RPM multiplier

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Date:	Sun, 21 Dec 2014 16:55:51 +0000
From:	Steven Honeyman <stevenhoneyman@...il.com>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Guenter Roeck <linux@...ck-us.net>, Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Jean Delvare <jdelvare@...e.de>,
	Gabriele Mazzotta <gabriele.mzt@...il.com>,
	Jochen Eisinger <jochen@...guin-breeder.org>
Subject: Re: [PATCH v3] i8k: Autodetect maximal fan speed and fan RPM multiplier

On 21 December 2014 at 16:37, Pali Rohár <pali.rohar@...il.com> wrote:
> On Sunday 21 December 2014 13:23:32 Guenter Roeck wrote:
>> On 12/21/2014 04:09 AM, Pali Rohár wrote:
>> > On Sunday 21 December 2014 12:57:08 Guenter Roeck wrote:
>> >>> -#define I8K_FAN_MULT             30
>> >>> +#define I8K_FAN_MAX_RPM          30000
>> >>>
>> >>>    #define I8K_MAX_TEMP           127
>> >>>
>> >>>    #define I8K_FN_NONE            0x00
>> >>>
>> >>> @@ -64,7 +66,7 @@ static DEFINE_MUTEX(i8k_mutex);
>> >>>
>> >>>    static char bios_version[4];
>> >>>    static struct device *i8k_hwmon_dev;
>> >>>    static u32 i8k_hwmon_flags;
>> >>>
>> >>> -static int i8k_fan_mult;
>> >>> +static int i8k_fan_mult = 30;
>> >>
>> >> Why did you drop I8K_FAN_MULT ?
>> >
>> > Because I think it is not needed anymore... It is used only
>> > in one place (there ^). But if you want I can revert it
>> > back.
>>
>> That is not a reason to drop a define.
>>
>> >>>    static int __init i8k_probe(void)
>> >>>    {
>> >>>
>> >>> + const struct i8k_config_data *conf;
>> >>
>> >> Why did you move this variable declaration ?
>> >
>> > Comes from previous version of patches where I moved all
>> > variables to start of function. I will revert this change.
>> >
>> >>> -         const struct i8k_config_data *conf = id->driver_data;
>> >>> +         conf = id->driver_data;
>> >>> +         if (fan_mult <= 0 && conf->fan_mult > 0)
>> >>
>> >> I still don't see the value in accepting fan_mult < 0
>> >> (compeared to == 0).
>> >
>> > Ok. What kernel driver should do if user load it with
>> > negative parameter? We should not propagate negative value
>> > to functions.
>>
>> You have multiple options: Ignore it (bad idea ;-), abort
>> loading the module with -EINVAL, or make the module parameter
>> an unsigned.
>>
>
> And how to make module parameter as unsigned? It is possible?
>
> Code
>
> module_param(fan_mult, unsigned int, 0);
>
> cause compile error:
>
> i8k.c:99:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘int’
> i8k.c:99:1: error: ‘param_ops_unsigned’ undeclared here (not in a function)


module_param(fan_mult, uint, 0);


Steven.
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