Re: [PATCH 9/10 v2] Generic Watchdog Timer Driver

From: Arnd Bergmann
Date: Sat Jun 18 2011 - 15:18:24 EST

On Saturday 18 June 2011 19:27:27 Wim Van Sebroeck wrote:
> watchdog: WatchDog Timer Driver Core - Part 9
> Add support for extra ioctl calls by adding a
> ioctl watchdog operation. This operation will be
> called before we do our own handling of ioctl
> commands. This way we can override the internal
> ioctl command handling and we can also add
> extra ioctl commands. The ioctl watchdog operation
> should return the appropriate error codes or
> -ENOIOCTLCMD if the ioctl command should be handled
> through the internal ioctl handling of the framework.
> Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxx>

Hmm, I'm not sure about this one. It does make the conversion
of existing drivers easier but doesn't encourage doing a good
job there.

How about instead providing a compatibility helper module that
provides helper functions like this:

int watchdog_compat_getstatus(struct watchdog_device *wdd)
int __user *tmp = compat_alloc_userspace(sizeof (int));
int ret;

ret = wdd->ops->ioctl(wdd, WDIOC_GETSTATUS, tmp);
if (ret)
return ret;

__get_user(ret, tmp);
return ret;

This would let you use the common ioctl implementation for all
watchdogs without the option of an individual driver overriding
it, but a driver could still provide an ioctl method that only
gets called by the watchdog_compat_* functions.

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