[PATCH 2/2] gpiolib: Defer gpio device setup until after gpiolib initialization

Guenter Roeck
2016-03-31T15:12:01Z

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. This happens because gpio_bus_type has not been
registered yet. Defer creating gpio devices until after gpiolib has
been initialized to fix the problem.

Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Alexandre Courbot <gnurou@gmail.com>
Fixes: ff2b13592299 ("gpio: make the gpiochip a real device")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
drivers/gpio/gpiolib.c | 98 ++++++++++++++++++++++++++++++++++----------------
1 file changed, 67 insertions(+), 31 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f1531070814d..8bb24dc8dc3d 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)
{
@@ -445,6 +446,58 @@ static void gpiodevice_release(struct device *dev)
kfree(gdev);
}

+static int gpiochip_setup_dev(struct gpio_device *gdev)
+{
+ int status;
+
+ cdev_init(&gdev->chrdev, &gpio_fileops);
+ gdev->chrdev.owner = THIS_MODULE;
+ gdev->chrdev.kobj.parent = &gdev->dev.kobj;
+ gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
+ status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
+ if (status < 0)
+ chip_warn(gdev->chip, "failed to add char device %d:%d\n",
+ MAJOR(gpio_devt), gdev->id);
+ else
+ chip_dbg(gdev->chip, "added GPIO chardev (%d:%d)\n",
+ MAJOR(gpio_devt), gdev->id);
+ status = device_add(&gdev->dev);
+ if (status)
+ goto err_remove_chardev;
+
+ status = gpiochip_sysfs_register(gdev);
+ if (status)
+ goto err_remove_device;
+
+ /* From this point, the .release() function cleans up gpio_device */
+ gdev->dev.release = gpiodevice_release;
+ get_device(&gdev->dev);
+ pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
+ __func__, gdev->base, gdev->base + gdev->ngpio - 1,
+ dev_name(&gdev->dev), gdev->chip->label ? : "generic");
+
+ return 0;
+
+err_remove_device:
+ device_del(&gdev->dev);
+err_remove_chardev:
+ cdev_del(&gdev->chrdev);
+ return status;
+}
+
+static void gpiochip_setup_devs(void)
+{
+ struct gpio_device *gdev;
+ int err;
+
+ list_for_each_entry(gdev, &gpio_devices, list) {
+ err = gpiochip_setup_dev(gdev);
+ if (err)
+ pr_err("%s: Failed to initialize gpio device (%d)\n",
+ dev_name(&gdev->dev), err);
+ }
+}
+
/**
* gpiochip_add_data() - register a gpio_chip
* @chip: the chip to register, with chip->base initialized
@@ -459,6 +512,9 @@ 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.
*/
@@ -515,7 +571,7 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
if (chip->ngpio == 0) {
chip_err(chip, "tried to insert a GPIO chip with zero lines\n");
status = -EINVAL;
- goto err_free_gdev;
+ goto err_free_descs;
}

if (chip->label)
@@ -597,39 +653,16 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
* we get a device node entry in sysfs under
* /sys/bus/gpio/devices/gpiochipN/dev that can be used for
* coldplug of device nodes and other udev business.
+ * We can do this only if gpiolib has been initialized.
+ * Otherwise, defer until later.
*/
- cdev_init(&gdev->chrdev, &gpio_fileops);
- gdev->chrdev.owner = THIS_MODULE;
- gdev->chrdev.kobj.parent = &gdev->dev.kobj;
- gdev->dev.devt = MKDEV(MAJOR(gpio_devt), gdev->id);
- status = cdev_add(&gdev->chrdev, gdev->dev.devt, 1);
- if (status < 0)
- chip_warn(chip, "failed to add char device %d:%d\n",
- MAJOR(gpio_devt), gdev->id);
- else
- chip_dbg(chip, "added GPIO chardev (%d:%d)\n",
- MAJOR(gpio_devt), gdev->id);
- status = device_add(&gdev->dev);
- if (status)
- goto err_remove_chardev;
-
- status = gpiochip_sysfs_register(gdev);
- if (status)
- goto err_remove_device;
-
- /* From this point, the .release() function cleans up gpio_device */
- gdev->dev.release = gpiodevice_release;
- get_device(&gdev->dev);
- pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
- __func__, gdev->base, gdev->base + gdev->ngpio - 1,
- dev_name(&gdev->dev), chip->label ? : "generic");
-
+ if (gpiolib_initialized) {
+ status = gpiochip_setup_dev(gdev);
+ if (status)
+ goto err_remove_chip;
+ }
return 0;

-err_remove_device:
- device_del(&gdev->dev);
-err_remove_chardev:
- cdev_del(&gdev->chrdev);
err_remove_chip:
acpi_gpiochip_remove(chip);
gpiochip_free_hogs(chip);
@@ -2834,6 +2867,9 @@ 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;
+ gpiochip_setup_devs();
}
return ret;
}
--
2.5.0