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

Boris Brezillon
2018-07-03T17:31:41Z

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...

Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>

Regards,

Boris