Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] reset: allow to pass NULL pointer to reset_control_put() | Date | Wed, 04 May 2016 14:47:31 +0200 |
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On Wednesday 04 May 2016 14:34:43 Philipp Zabel wrote: > 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;
Sounds good to me too. We'd still have to think about whatever Masahiro was trying to do and how his caller should be written, but hopefully there is a good solution.
> 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.
Ah, good. Could the above code just be converted into a variation of device_reset() that takes the name of a reset line?
Arnd
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