gpiolib: cdev: fix frame size warning in gpio_ioctl()

The kernel test robot reports the following warning in [1]:

 drivers/gpio/gpiolib-cdev.c: In function 'gpio_ioctl':
 >>drivers/gpio/gpiolib-cdev.c:1437:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]

Refactor gpio_ioctl() to handle each ioctl in its own helper function
and so reduce the variables stored on the stack to those explicitly
required to service the ioctl at hand.

The lineinfo_get_v1() helper handles both the GPIO_GET_LINEINFO_IOCTL
and GPIO_GET_LINEINFO_WATCH_IOCTL, as per the corresponding v2
implementation - lineinfo_get().

[1] https://lore.kernel.org/lkml/202012270910.VW3qc1ER-lkp@intel.com/

Fixes: aad955842d1c ("gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 12b679ca552cccea423e04874e1f2e3c11bef7a6..1a7b51163528b5a29bfb9c201459a3c959a21d9a 100644 (file)
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -1979,6 +1979,21 @@ struct gpio_chardev_data {
 #endif
 };
 
+static int chipinfo_get(struct gpio_chardev_data *cdev, void __user *ip)
+{
+       struct gpio_device *gdev = cdev->gdev;
+       struct gpiochip_info chipinfo;
+
+       memset(&chipinfo, 0, sizeof(chipinfo));
+
+       strscpy(chipinfo.name, dev_name(&gdev->dev), sizeof(chipinfo.name));
+       strscpy(chipinfo.label, gdev->label, sizeof(chipinfo.label));
+       chipinfo.lines = gdev->ngpio;
+       if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
+               return -EFAULT;
+       return 0;
+}
+
 #ifdef CONFIG_GPIO_CDEV_V1
 /*
  * returns 0 if the versions match, else the previously selected ABI version
@@ -1993,6 +2008,41 @@ static int lineinfo_ensure_abi_version(struct gpio_chardev_data *cdata,
 
        return abiv;
 }
+
+static int lineinfo_get_v1(struct gpio_chardev_data *cdev, void __user *ip,
+                          bool watch)
+{
+       struct gpio_desc *desc;
+       struct gpioline_info lineinfo;
+       struct gpio_v2_line_info lineinfo_v2;
+
+       if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
+               return -EFAULT;
+
+       /* this doubles as a range check on line_offset */
+       desc = gpiochip_get_desc(cdev->gdev->chip, lineinfo.line_offset);
+       if (IS_ERR(desc))
+               return PTR_ERR(desc);
+
+       if (watch) {
+               if (lineinfo_ensure_abi_version(cdev, 1))
+                       return -EPERM;
+
+               if (test_and_set_bit(lineinfo.line_offset, cdev->watched_lines))
+                       return -EBUSY;
+       }
+
+       gpio_desc_to_lineinfo(desc, &lineinfo_v2);
+       gpio_v2_line_info_to_v1(&lineinfo_v2, &lineinfo);
+
+       if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
+               if (watch)
+                       clear_bit(lineinfo.line_offset, cdev->watched_lines);
+               return -EFAULT;
+       }
+
+       return 0;
+}
 #endif
 
 static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
@@ -2030,6 +2080,22 @@ static int lineinfo_get(struct gpio_chardev_data *cdev, void __user *ip,
        return 0;
 }
 
+static int lineinfo_unwatch(struct gpio_chardev_data *cdev, void __user *ip)
+{
+       __u32 offset;
+
+       if (copy_from_user(&offset, ip, sizeof(offset)))
+               return -EFAULT;
+
+       if (offset >= cdev->gdev->ngpio)
+               return -EINVAL;
+
+       if (!test_and_clear_bit(offset, cdev->watched_lines))
+               return -EBUSY;
+
+       return 0;
+}
+
 /*
  * gpio_ioctl() - ioctl handler for the GPIO chardev
  */
@@ -2037,80 +2103,24 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
        struct gpio_chardev_data *cdev = file->private_data;
        struct gpio_device *gdev = cdev->gdev;
-       struct gpio_chip *gc = gdev->chip;
        void __user *ip = (void __user *)arg;
-       __u32 offset;
 
        /* We fail any subsequent ioctl():s when the chip is gone */
-       if (!gc)
+       if (!gdev->chip)
                return -ENODEV;
 
        /* Fill in the struct and pass to userspace */
        if (cmd == GPIO_GET_CHIPINFO_IOCTL) {
-               struct gpiochip_info chipinfo;
-
-               memset(&chipinfo, 0, sizeof(chipinfo));
-
-               strscpy(chipinfo.name, dev_name(&gdev->dev),
-                       sizeof(chipinfo.name));
-               strscpy(chipinfo.label, gdev->label,
-                       sizeof(chipinfo.label));
-               chipinfo.lines = gdev->ngpio;
-               if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
-                       return -EFAULT;
-               return 0;
+               return chipinfo_get(cdev, ip);
 #ifdef CONFIG_GPIO_CDEV_V1
-       } else if (cmd == GPIO_GET_LINEINFO_IOCTL) {
-               struct gpio_desc *desc;
-               struct gpioline_info lineinfo;
-               struct gpio_v2_line_info lineinfo_v2;
-
-               if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
-                       return -EFAULT;
-
-               /* this doubles as a range check on line_offset */
-               desc = gpiochip_get_desc(gc, lineinfo.line_offset);
-               if (IS_ERR(desc))
-                       return PTR_ERR(desc);
-
-               gpio_desc_to_lineinfo(desc, &lineinfo_v2);
-               gpio_v2_line_info_to_v1(&lineinfo_v2, &lineinfo);
-
-               if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
-                       return -EFAULT;
-               return 0;
        } else if (cmd == GPIO_GET_LINEHANDLE_IOCTL) {
                return linehandle_create(gdev, ip);
        } else if (cmd == GPIO_GET_LINEEVENT_IOCTL) {
                return lineevent_create(gdev, ip);
-       } else if (cmd == GPIO_GET_LINEINFO_WATCH_IOCTL) {
-               struct gpio_desc *desc;
-               struct gpioline_info lineinfo;
-               struct gpio_v2_line_info lineinfo_v2;
-
-               if (copy_from_user(&lineinfo, ip, sizeof(lineinfo)))
-                       return -EFAULT;
-
-               /* this doubles as a range check on line_offset */
-               desc = gpiochip_get_desc(gc, lineinfo.line_offset);
-               if (IS_ERR(desc))
-                       return PTR_ERR(desc);
-
-               if (lineinfo_ensure_abi_version(cdev, 1))
-                       return -EPERM;
-
-               if (test_and_set_bit(lineinfo.line_offset, cdev->watched_lines))
-                       return -EBUSY;
-
-               gpio_desc_to_lineinfo(desc, &lineinfo_v2);
-               gpio_v2_line_info_to_v1(&lineinfo_v2, &lineinfo);
-
-               if (copy_to_user(ip, &lineinfo, sizeof(lineinfo))) {
-                       clear_bit(lineinfo.line_offset, cdev->watched_lines);
-                       return -EFAULT;
-               }
-
-               return 0;
+       } else if (cmd == GPIO_GET_LINEINFO_IOCTL ||
+                  cmd == GPIO_GET_LINEINFO_WATCH_IOCTL) {
+               return lineinfo_get_v1(cdev, ip,
+                                      cmd == GPIO_GET_LINEINFO_WATCH_IOCTL);
 #endif /* CONFIG_GPIO_CDEV_V1 */
        } else if (cmd == GPIO_V2_GET_LINEINFO_IOCTL ||
                   cmd == GPIO_V2_GET_LINEINFO_WATCH_IOCTL) {
@@ -2119,16 +2129,7 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
        } else if (cmd == GPIO_V2_GET_LINE_IOCTL) {
                return linereq_create(gdev, ip);
        } else if (cmd == GPIO_GET_LINEINFO_UNWATCH_IOCTL) {
-               if (copy_from_user(&offset, ip, sizeof(offset)))
-                       return -EFAULT;
-
-               if (offset >= cdev->gdev->ngpio)
-                       return -EINVAL;
-
-               if (!test_and_clear_bit(offset, cdev->watched_lines))
-                       return -EBUSY;
-
-               return 0;
+               return lineinfo_unwatch(cdev, ip);
        }
        return -EINVAL;
 }