Re: Query: Best way to know if a watchdog is active (kicked)

[Pratyush Anand <panand@redhat.com>]

On 21/08/2015:08:19:03 AM, Guenter Roeck wrote:
> On Fri, Aug 21, 2015 at 02:22:17PM +0530, Pratyush Anand wrote:
> > On 18/08/2015:07:23:38 AM, Guenter Roeck wrote:
> > > Sounds good. We should have a 'name' attribute as well. We'll also need
> > > 'timeout', 'keepalive' to ping the watchdog, 'timeleft', and 'bootstatus'.
> > > Not sure what else.
> > > 
> > > The attributes should be implemented as class attributes, to ensure
> > > that they are created and removed automatically. That may require
> > > the watchdog class to be static instead of a pointer.
> > 
> > Should n't attributes be implemented as device attribute as they are properties
> > of each device. Under the class watchdog_class, we can have multiple device on a
> > system, and these attributes would be different for different devices. So, what
> > I am thinking is to create device in __watchdog_register_device using
> > device_create_with_groups instead of device_create. Here we can link a
> > attribute_group with all attributes you suggested.
> > 
> Class attibutes are created automatically for each device registered which is
> a member of the class. They are attached to the device, not to the class.

Not sure, if we both are referring to same thing..
So, I did a basic testing. I changed "static struct class *watchdog_class;" to "tatic
struct class watchdog_class" and other than .name and .owner I added
.class_attrs and then further added one node "state" in this class_attrs.

I have two watchdog in my system, so I was expecting
/sys/class/watchdog/watchdog0/state and /sys/class/watchdog/watchdog1/state. But
I see that there is only /sys/class/watchdog/state with the above approach.

> In other words, the infrastructure creates the attributes, the driver doesn't
> have to do it, and there is no race condition where the device exists but
> the attributes are not yet there.

Yes, I agree that individual driver does not need to do anything.
watchdog_core.c and watchdog_dev.c will take care for each of the device
registered with it. I am able to do that, but not using .class_attrs,
rather using device_create_with_groups.

> 
> Not sure what you mean with "different". Can you elaborate ?

As I said above, with the "different" I meant that we should have state in each
/sys/class/watchdog/watchdogn.

~Pratyush