Re: Question about hwmon_attr_show_string

From	Guenter Roeck <linux@roeck-us.net>
Newsgroups	linux.kernel
Subject	Re: Question about hwmon_attr_show_string
Date	2017-03-07 01:00 +0100
Message-ID	<tiaHL-7eE-3@gated-at.bofh.it> (permalink)
References	<tgJqh-1AZ-1@gated-at.bofh.it> <ti7JU-5av-21@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Mar 06, 2017 at 09:48:35PM +0100, Peter Hüwe wrote:
> Hi Guenter,
> 
> I was wondering whether there was a particular reason why 
> hwmon_attr_show_string passes only an "empty" pointer(pointer) to the ops-
> >read_string function rather than the buffer itself?
> 
> Wouldn't this mean that in ops->read_string I'd have to reserve some space for 
> the value on the heap (and taking care to free it somewhere, since returning 
> an address on the stack is bad idea), instead of calling sprintf(buf, "%s\n", 
> s) directly?
> 
> With the current implementation I have to sprintf it into my local buffer and 
> you sprintf it again into the final buffer.
> 
The idea was that the called code would return a pointer to a constant string,
ie one that isn't changing from call to call.

What attribute do you see that would require a dynamic (changing) string ?

Thanks,
Guenter

Thread

Conversion of w83627ehf to hwmon_device_register_with_info ? Peter Hüwe <PeterHuewe@gmx.de> - 2017-03-03 01:40 +0100
  Re: Conversion of w83627ehf to hwmon_device_register_with_info ? Guenter Roeck <linux@roeck-us.net> - 2017-03-03 04:00 +0100
  Re: Conversion of w83627ehf to hwmon_device_register_with_info ? Jean Delvare <jdelvare@suse.de> - 2017-03-03 16:10 +0100
  Question about hwmon_attr_show_string Peter Hüwe <PeterHuewe@gmx.de> - 2017-03-06 21:50 +0100
    Re: Question about hwmon_attr_show_string Guenter Roeck <linux@roeck-us.net> - 2017-03-07 01:00 +0100
      Re: Question about hwmon_attr_show_string Jean Delvare <jdelvare@suse.de> - 2017-03-07 10:20 +0100
        Re: Question about hwmon_attr_show_string Peter Huewe <peterhuewe@gmx.de> - 2017-03-07 10:30 +0100
        Re: Question about hwmon_attr_show_string Guenter Roeck <linux@roeck-us.net> - 2017-03-07 16:10 +0100

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