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SubjectRe: question about drivers/pinctrl/pinctrl-at91.c
On Tue, 11 Dec 2012, Linus Walleij wrote:

> On Sat, Dec 8, 2012 at 4:52 PM, Julia Lawall <julia.lawall@lip6.fr> wrote:
>
> > The function at91_dt_node_to_map in drivers/pinctrl/pinctrl-at91.c contains
> > the following code:
> >
> > new_map = devm_kzalloc(pctldev->dev, sizeof(*new_map) * map_num,
> > GFP_KERNEL);
> > if (!new_map)
> > return -ENOMEM;
> >
> > *map = new_map;
> > *num_maps = map_num;
> >
> > /* create mux map */
> > parent = of_get_parent(np);
> > if (!parent) {
> > kfree(new_map);
> > return -EINVAL;
> > }
> >
> > This is clearly not correct, because the combination of devm_kzalloc and
> > kfree risks creating a double free.
>
> Agreed, probably just some spurious leftover.
>
> > But I am not sure how best to fix it.
> > Is the data structure intended to normally exist until the driver's remove
> > function is called? If so, perhaps the devm_kzalloc is OK. If I just
> > remove the kfree, then the structure will persist until the remove function
> > is called, even though there was an error, which is perhaps not good. So I
> > could change the kfree to devm_kfree?
>
> I was under the impression that if you exit the probe function
> with a negative value anything allocated with devm_* was freed
> immediately, that is atleast how it's described in
> Documentation/driver-model/devres.txt
> atleast that seems to be the intetion with the whole thing.

That is true, but I wasn't sure taht this function was part of the probe
function. Its only reference is in:

static struct pinctrl_ops at91_pctrl_ops = {
.get_groups_count = at91_get_groups_count,
.get_group_name = at91_get_group_name,
.get_group_pins = at91_get_group_pins,
.pin_dbg_show = at91_pin_dbg_show,
.dt_node_to_map = at91_dt_node_to_map,
.dt_free_map = at91_dt_free_map,
};

Working backwards, one possible call site is pinctrl_get, which is an
exported function. Is it safe to assume that it will always be called
from within a probe function?

thanks,
julia


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