linux-kernel - [PATCH] gpio: Do not accept gpio chip additions before gpiolib initialization

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Date:	Tue, 29 Mar 2016 11:20:38 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Alexandre Courbot <gnurou@...il.com>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH] gpio: Do not accept gpio chip additions before gpiolib initialization

Since commit ff2b13592299 ("gpio: make the gpiochip a real device"),
attempts to add a gpio chip prior to gpiolib initialization cause the
system to crash. Dump a warning to the console and return an error
if the situation is encountered.

Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 drivers/gpio/gpiolib.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 72065532c1c7..ac66219f0611 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -68,6 +68,7 @@ LIST_HEAD(gpio_devices);
 static void gpiochip_free_hogs(struct gpio_chip *chip);
 static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
 
+static bool gpiolib_initialized;
 
 static inline void desc_set_label(struct gpio_desc *d, const char *label)
 {
@@ -457,6 +458,9 @@ static void gpiodevice_release(struct device *dev)
  * the gpio framework's arch_initcall().  Otherwise sysfs initialization
  * for GPIOs will fail rudely.
  *
+ * gpiochip_add_data() must only be called after gpiolib initialization,
+ * ie after core_initcall().
+ *
  * If chip->base is negative, this requests dynamic assignment of
  * a range of valid GPIOs.
  */
@@ -468,6 +472,11 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 	int		base = chip->base;
 	struct gpio_device *gdev;
 
+	if (!gpiolib_initialized) {
+		WARN(1, "gpiolib not initialized\n");
+		return -EPROBE_DEFER;
+	}
+
 	/*
 	 * First: allocate and populate the internal stat container, and
 	 * set up the struct device.
@@ -2829,6 +2838,8 @@ static int __init gpiolib_dev_init(void)
 	if (ret < 0) {
 		pr_err("gpiolib: failed to allocate char dev region\n");
 		bus_unregister(&gpio_bus_type);
+	} else {
+		gpiolib_initialized = true;
 	}
 	return ret;
 }
-- 
2.5.0