Re: [Patch v2 1/2] gpio: add GPIO hogging mechanism

Maxime Ripard
2014-12-01T16:40:07Z

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Hi,

On Fri, Nov 28, 2014 at 04:30:01PM +0900, Alexandre Courbot wrote:
> > +/**
> > + * do_gpio_hog - Given node is a GPIO hog configuration, handle it
> > + * @np: device node to get GPIO from
> > + *
> > + * This is only used by of_gpiochip_add to request/set GPIO initial
> > + * configuration.
> > + */
> > +static int do_gpio_hog(struct device_node *np)
> > +{
> > + struct gpio_desc *desc = NULL;
> > + int err;
> > + const char *name;
> > + enum gpio_lookup_flags lflags;
> > + enum gpiod_flags dflags;
> > +
> > + desc = of_get_gpio_hog(np, &name, &lflags, &dflags);
> > + if (!desc)
> > + return -ENOTSUPP;
> > + else if (IS_ERR(desc))
> > + return PTR_ERR(desc);
> > +
> > + err = gpiod_request(desc, name);
>
> Using this function means that a GPIO chip module cannot be unloaded
> if it uses GPIO hogs. Is it the intended behavior? If not, please use
> gpiochip_request_own_desc() instead, and make sure to call
> gpiochip_free_own_desc() for each hog when the driver is unloaded.

The only thing I'd like to have would be that the request here would
be non-exclusive, so that a later driver would still be allowed later
on to request that GPIO later on and manage it itself (ideally using
the usual gpiod_request function).

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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