Re: çå: [v2,1/1] hwmon: (nct7904) Add watchdog function

[Guenter Roeck]

On 3/26/20 7:39 PM, yuechao.zhao(赵越超) wrote:
> Hi Guenter
> Thank you very much for the suggestion
> 
> But, I wish to consult you on a few questions.
> The NCT7904 is very special in watchdog function. Its minimum unit is minutes.
> So, what unit do we use for setting the timeout in user space. Minutes or seconds?
> Does the kernel document specify it?
> 
Documentation/watchdog/watchdog-api.rst very clearly specifies that
the timeout is set in seconds.

> Also, about this suggestion:
> 	> +	data->wdt.timeout = timeout * 60; /* in seconds */
> 	> +	data->wdt.min_timeout = 1;
> 	> +	data->wdt.max_timeout = 15300;
> 	Please make it 60 * 255 (or use a respective define) to clarify where the number comes from.
> 
> The reason for not use 60 * 255(or use a respective define ) is that we will set the default timeout with 
> "timeout" parameter when "insmod nct7904.ko".

This is not an argument for
	data->wdt.max_timeout = 15300;
instead of
	data->wdt.max_timeout = 60 * 255;
or

#define MAX_TIMEOUT	(60 * 255)
...
	data->wdt.max_timeout = MAX_TIMEOUT;

> The relevant code as follows:
> 	> +static int timeout = WATCHDOG_TIMEOUT; module_param(timeout, int, 0); 
> 	> +MODULE_PARM_DESC(timeout, "Watchdog timeout in minutes. 1 <= timeout <= 255, default="
> 	> +			__MODULE_STRING(WATCHODOG_TIMEOUT) ".");
> 

I accepted that you want to have a module parameter which specifies
the timeout in minutes instead of seconds (as would be customary).
However, I completely fail to understand what that has to do with
using an unexplained constant of "15300" when setting the maximum
timeout variable instead of "60 * 255" or, as I had suggested, a
define.

Thanks,
Guenter