[PATCH v1 1/1] media: ov7251: Remap "reset" to "enable" for OV7251

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

The driver of OmniVision OV7251 expects "enable" pin instead of "reset".
Remap "reset" to "enable" and update polarity.

In particular, the Linux kernel can't load the camera sensor
driver on Microsoft Surface Book without this change:

 ov7251 i2c-INT347E:00: supply vdddo not found, using dummy regulator
 ov7251 i2c-INT347E:00: supply vddd not found, using dummy regulator
 ov7251 i2c-INT347E:00: supply vdda not found, using dummy regulator
 ov7251 i2c-INT347E:00: cannot get enable gpio
 ov7251 i2c-INT347E:00: probe with driver ov7251 failed with error -2

Suggested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/media/i2c/ov7251.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/media/i2c/ov7251.c b/drivers/media/i2c/ov7251.c
index 30f61e04ecaf..7b35add1e0ed 100644
--- a/drivers/media/i2c/ov7251.c
+++ b/drivers/media/i2c/ov7251.c
@@ -1696,7 +1696,21 @@ static int ov7251_probe(struct i2c_client *client)
 		return PTR_ERR(ov7251->analog_regulator);
 	}
 
+	/*
+	 * The device-tree bindings call this pin "enable", but the
+	 * datasheet describes the pin as "reset (active low with internal
+	 * pull down resistor)". The ACPI tables describing this sensor
+	 * on, e.g., the Microsoft Surface Book use the ACPI equivalent of
+	 * "reset" as pin name, which ACPI glue code then maps to "reset".
+	 * Check for a "reset" pin if there is no "enable" pin.
+	 */
 	ov7251->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(ov7251->enable_gpio) &&
+	    PTR_ERR(ov7251->enable_gpio) != -EPROBE_DEFER) {
+		ov7251->enable_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+		if (!IS_ERR(ov7251->enable_gpio))
+			gpiod_toggle_active_low(ov7251->enable_gpio);
+	}
 	if (IS_ERR(ov7251->enable_gpio)) {
 		dev_err(dev, "cannot get enable gpio\n");
 		return PTR_ERR(ov7251->enable_gpio);
-- 
2.43.0.rc1.1336.g36b5255a03ac