Re: [PATCH] gpiolib: Defer on non-DT find_chip_by_name() failure

Janusz Krzysztofik
2018-07-04T19:13:42Z

On Tuesday, July 3, 2018 7:31:41 PM CEST Boris Brezillon wrote:
> Hi Janusz,
>
> On Tue, 3 Jul 2018 19:26:35 +0200
>
> Janusz Krzysztofik <jmkrzyszt@gmail.com> wrote:
> > Avoid replication of error code conversion in non-DT GPIO consumers'
> > code by returning -EPROBE_DEFER from gpiod_find() in case a chip
> > identified by its label in a registered lookup table is not ready.
> >
> > See https://lkml.org/lkml/2018/5/30/176 for example case.
> >
> > Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
> > ---
> > If accepted, please add
> >
> > Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
> >
> > if Boris doesn't mind.
> >
> > Thanks,
> > Janusz
> >
> > drivers/gpio/gpiolib.c | 13 ++++++++++---
> > 1 file changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index e11a3bb03820..15dc77c80328 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -3639,9 +3639,16 @@ static struct gpio_desc *gpiod_find(struct device
> > *dev, const char *con_id,>
> > chip = find_chip_by_name(p->chip_label);
> >
> > if (!chip) {
> >
> > - dev_err(dev, "cannot find GPIO chip %s\n",
> > - p->chip_label);
> > - return ERR_PTR(-ENODEV);
> > + /*
> > + * As the lookup table indicates a chip with
> > + * p->chip_label should exist, assume it may
> > + * still appear latar and let the interested
>
> ^ later
>
> > + * consumer be probed again or let the Deferred
> > + * Probe infrastructure handle the error.
> > + */
> > + dev_warn(dev, "cannot find GPIO chip %s, deferring\n",
> > + p->chip_label);
> > + return ERR_PTR(-EPROBE_DEFER);
> >
> > }
> >
> > if (chip->ngpio <= p->chip_hwnum) {
>
> Looks good otherwise. Let's hope we're not breaking implementations
> testing for -ENODEV...

I've reviewed them all and found two which I think may be affected:
- drivers/mfd/arizona-core.c,
- drivers/i2c/busses/i2c-imx.c.
As far as I can understand the code, both depend on error != -EPROBE_DEFER in
order to continue in degraded mode. I'm adding their maintainers to the loop.

Thanks,
Janusz