Re: watchdog ioctl inconsistencies

[Guenter Roeck <linux@roeck-us.net>]

On 8/26/19 5:54 AM, Rasmus Villemoes wrote:
> Hi,
> 
> uapi/linux/watchdog.h has these
> 
> #define WDIOC_SETOPTIONS        _IOR(WATCHDOG_IOCTL_BASE, 4, int)
> 
> This is a write from userspace perspective, so should have been _IOW.
> 
> #define WDIOC_KEEPALIVE         _IOR(WATCHDOG_IOCTL_BASE, 5, int)
> 
> This one doesn't actually take an argument, so should just have been an
> _IO - or if anything, an _IOW. One could be misled to think that if the
> int argument has 'V' somewhere (perhaps first or last byte, depending on
> endianness) that would count as a magic close.
> 
> #define WDIOC_SETTIMEOUT        _IOWR(WATCHDOG_IOCTL_BASE, 6, int)
> #define WDIOC_SETPRETIMEOUT     _IOWR(WATCHDOG_IOCTL_BASE, 8, int)
> 
> The SETTIMEOUT handling does fall through to the GETTIMEOUT case, so
> that one is indeed a "write this, but tell me what value actually took
> effect". The SETPRETIMEOUT case ends with a break, so that one is really
> _IOW.
> 
> There's not much to do about these, I think, but perhaps one could add a
> comment to the uapi header containing the magic explains-all phrase
> "historical reasons".
> 
Those ioctls were imported into git when the git repository was created.
I don't think it is worth bothering about it now. I also don't think it
would add much if any value to add "historic reason" comments.

Guenter