[PATCH] w1-gpio: handle of_get_gpio() returning -EPROBE_DEFER better

Uwe Kleine-König
2014-02-13T22:05:44Z

of_get_gpio() might return -EPROBE_DEFER meaning that the driver
providing the gpio isn't ready yet. If that happens for the first gpio
the resulting kernel output without this patch is:

w1-gpio somename: Failed to parse DT
platform somename: Driver w1-gpio requests probe deferral

The first message is misleading and so is suppressed with this patch.

Further if determining the gpio to switch the external pullup yields
-EPROBE_DEFER this error should be passed back to the caller instead of
just continuing without pullup.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
Actually I'm not completely happy with this change because IMHO if a
device tree node contains:

gpios = <&gpio5 0 0 4>;

where gpio5's #gpio-cells property is <2> I'd prefer to not bind the
driver with an error message instead of treating it as if

gpios = <&gpio5 0 0>;

was specified. Still this patch is a correct first step.

So something like that would be nice:

len = get_len_of_gpio_array();
if (len < 0)
/* not well-formed */
return len;

if (len == 1)
go on without pullup
else if (len == 2)
go on with pullup
else
scream
---
drivers/w1/masters/w1-gpio.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/w1/masters/w1-gpio.c b/drivers/w1/masters/w1-gpio.c
index e36b18b2817b..4b581228a4d9 100644
--- a/drivers/w1/masters/w1-gpio.c
+++ b/drivers/w1/masters/w1-gpio.c
@@ -68,11 +68,22 @@ static int w1_gpio_probe_dt(struct platform_device *pdev)
pdata->is_open_drain = 1;

gpio = of_get_gpio(np, 0);
- if (gpio < 0)
+ if (gpio < 0) {
+ if (gpio != -EPROBE_DEFER)
+ dev_err(&pdev->dev,
+ "Failed to parse gpio property for data pin (%d)\n",
+ gpio);
+
return gpio;
+ }
pdata->pin = gpio;

- pdata->ext_pullup_enable_pin = of_get_gpio(np, 1);
+ gpio = of_get_gpio(np, 1);
+ if (gpio == -EPROBE_DEFER)
+ return gpio;
+ /* ignore other errors as the pullup gpio is optional */
+ pdata->ext_pullup_enable_pin = gpio;
+
pdev->dev.platform_data = pdata;

return 0;
@@ -86,10 +97,8 @@ static int w1_gpio_probe(struct platform_device *pdev)

if (of_have_populated_dt()) {
err = w1_gpio_probe_dt(pdev);
- if (err < 0) {
- dev_err(&pdev->dev, "Failed to parse DT\n");
+ if (err < 0)
return err;
- }
}

pdata = dev_get_platdata(&pdev->dev);
--
1.8.5.3