Messages in this thread | | | Subject | Re: [PATCH] reset: allow to pass NULL pointer to reset_control_put() | From | Philipp Zabel <> | Date | Wed, 04 May 2016 14:34:43 +0200 |
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Am Mittwoch, den 04.05.2016, 20:34 +0900 schrieb Masahiro Yamada: > Hi Arnd, > > 2016-05-04 20:24 GMT+09:00 Arnd Bergmann <arnd@arndb.de>: > > On Wednesday 04 May 2016 20:17:51 Masahiro Yamada wrote: > >> Currently, reset_control_put() just returns for error pointer, > >> but not for NULL pointer. This is not reasonable. > >> > >> Passing NULL pointer should be allowed as well to make failure path > >> handling easier. > >> > >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > >> --- > >> > >> drivers/reset/core.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/reset/core.c b/drivers/reset/core.c > >> index 181b05d..7bb16d1 100644 > >> --- a/drivers/reset/core.c > >> +++ b/drivers/reset/core.c > >> @@ -288,7 +288,7 @@ EXPORT_SYMBOL_GPL(reset_control_get); > >> > >> void reset_control_put(struct reset_control *rstc) > >> { > >> - if (IS_ERR(rstc)) > >> + if (IS_ERR_OR_NULL(rstc)) > >> return; > >> > >> module_put(rstc->rcdev->owner); > > > > Using IS_ERR_OR_NULL() normally indicates that there is something > > wrong with the API, or with the caller. > > > > What exactly is the idea behind treating an error pointer as a valid > > input to reset_control_put() here? Maybe it should just test for > > NULL?
The idea was that you could do drvdata->rstc = reset_control_get(...) in the probe() function and reset_control_put(drvdata->rstc) in remove() without having to check for IS_ERR(drvdata->rstc) again. I'm not convinced this is necessarily a good idea though. To simplify the teardown path we already have devm_reset_control_get().
> I thought about that a bit, > but there might be some (not nice) drivers that rely on the current behavior. > I did not want to break any boards with my patch. > > So, should it be > > if (!rstc) > return; > or, perhaps > > if (!rstc || WARN_ON_ONCE(IS_ERR(rstc))) > return; > > ?
NULL is not a valid input to reset_control, reset_control_get(_optional) should never return NULL.
I'd be in favor of turning this into
if (WARN_ON(IS_ERR_OR_NULL(rstc))) return;
As far as I am aware, ehci-tegra is the only driver that currently makes use of the IS_ERR(rstc) return in reset_control_put():
struct reset_control *usb1_reset;
usb1_reset = of_reset_control_get(phy_np, "usb"); if (IS_ERR(usb1_reset)) { /* ... */ } else { reset_control_assert(usb1_reset); udelay(1); reset_control_deassert(usb1_reset); } reset_control_put(usb1_reset);
That'd be trivial to fix.
regards Philipp
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