Re: [PATCH 1/6] driver-core : add class iteration api

Dave Young
2008-01-22T06:30:36Z

On Jan 22, 2008 2:24 PM, David Brownell <david-b@pacbell.net> wrote:
> On Monday 21 January 2008, Dave Young wrote:
> >
> > +/**
> > + * class_for_each_device - device iterator
> > + * @class: the class we're iterating
> > + * @data: data for the callback
> > + * @fn: function to be called for each device
> > + *
> > + * Iterate over @class's list of devices, and call @fn for each,
> > + * passing it @data.
> > + *
> > + * We check the return of @fn each time. If it returns anything
> > + * other than 0, we break out and return that value.
>
> I have a suggestion for better documentation, which
> applies to all these utilities:
>
>
> > + */
> > +int class_for_each_device(struct class *class, void *data,
> > + int (*fn)(struct device *, void *))
> > +{
> > + struct device *dev;
> > + int error = 0;
> > +
> > + if (!class)
> > + return -EINVAL;
> > + down(&class->sem);
> > + list_for_each_entry(dev, &class->devices, node) {
> > + dev = get_device(dev);
> > + if (dev) {
> > + error = fn(dev, data);
>
> This is called with class->sem held. So fn() has a
> constraint to not re-acquire that ... else it'd be
> self-deadlocking. I'd like to see docs at least
> mention that; calls to add or remove class members
> would be verboten, for example, which isn't an issue
> with most other driver model iterators.

Very good comment, thanks david. I will update after a while.

>
>
>
> > + put_device(dev);
> > + } else
> > + error = -ENODEV;
> > + if (error)
> > + break;
> > + }
> > + up(&class->sem);
> > +
> > + return error;
> > +}
> > +EXPORT_SYMBOL_GPL(class_for_each_device);
>