pinctrl: add checks for empty function names

This is needed as otherwise we can get the following when
dealing with buggy data in a pinmux driver for
pinmux_search_function:

Unable to handle kernel NULL pointer dereference at virtual
address 00000000
...
PC is at strcmp+0xc/0x34
LR is at pinmux_get+0x350/0x8f4
...

As we need pctldev initialized to call ops->list_functions,
let's initialize it before check_ops calls and pass the
pctldev to the check_ops functions. Do this for both pinmux
and pinconf check_ops functions.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index d9d35fc..8fe15cf 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -583,26 +583,6 @@
 	if (pctldesc->name == NULL)
 		return NULL;
 
-	/* If we're implementing pinmuxing, check the ops for sanity */
-	if (pctldesc->pmxops) {
-		ret = pinmux_check_ops(pctldesc->pmxops);
-		if (ret) {
-			pr_err("%s pinmux ops lacks necessary functions\n",
-			       pctldesc->name);
-			return NULL;
-		}
-	}
-
-	/* If we're implementing pinconfig, check the ops for sanity */
-	if (pctldesc->confops) {
-		ret = pinconf_check_ops(pctldesc->confops);
-		if (ret) {
-			pr_err("%s pin config ops lacks necessary functions\n",
-			       pctldesc->name);
-			return NULL;
-		}
-	}
-
 	pctldev = kzalloc(sizeof(struct pinctrl_dev), GFP_KERNEL);
 	if (pctldev == NULL)
 		return NULL;
@@ -617,6 +597,26 @@
 	mutex_init(&pctldev->gpio_ranges_lock);
 	pctldev->dev = dev;
 
+	/* If we're implementing pinmuxing, check the ops for sanity */
+	if (pctldesc->pmxops) {
+		ret = pinmux_check_ops(pctldev);
+		if (ret) {
+			pr_err("%s pinmux ops lacks necessary functions\n",
+			       pctldesc->name);
+			goto out_err;
+		}
+	}
+
+	/* If we're implementing pinconfig, check the ops for sanity */
+	if (pctldesc->confops) {
+		ret = pinconf_check_ops(pctldev);
+		if (ret) {
+			pr_err("%s pin config ops lacks necessary functions\n",
+			       pctldesc->name);
+			goto out_err;
+		}
+	}
+
 	/* Register all the pins */
 	pr_debug("try to register %d pins on %s...\n",
 		 pctldesc->npins, pctldesc->name);