gpiolib: Defer on non-DT find_chip_by_name() failure

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.

Suggested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 8ec51b7777c6b1b0c107b7869416794a2faafff5..a9a290999990edd54c65edf42f3f2a890837dc98 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3656,9 +3656,16 @@ 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 later and let the interested
+                        * 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) {