pinctrl: Don't copy function name when requesting a pin

Instead, store a pointer to the currently assigned function.

This allows us to delete the mux_requested variable from pin_desc; a pin
is requested if its currently assigned function is non-NULL.

When a pin is requested as a GPIO rather than a regular function, the
assigned function name is dynamically constructed. In this case, we have
to kstrdup() the dynamically constructed name, so that mux_function doesn't
pointed at stack data. This requires pin_free to be told whether to free
the mux_function pointer or not.

This removes the hard-coded maximum function name length.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

2 files changed, 24 insertions, 15 deletions

diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index e431aa537287..472fa1341cc0 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -59,8 +59,7 @@ struct pin_desc {
         spinlock_t lock;
         /* These fields only added when supporting pinmux drivers */
 #ifdef CONFIG_PINMUX
-        bool    mux_requested;
-        char    mux_function[16];
+        const char *mux_function;
 #endif
 };
 
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 90fb00d9a8a2..a5467f8709e9 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -130,14 +130,13 @@ static int pin_request(struct pinctrl_dev *pctldev,
         }
 
         spin_lock(&desc->lock);
-        if (desc->mux_requested) {
+        if (desc->mux_function) {
                 spin_unlock(&desc->lock);
                 dev_err(&pctldev->dev,
                         "pin already requested\n");
                 goto out;
         }
-        desc->mux_requested = true;
-        strncpy(desc->mux_function, function, sizeof(desc->mux_function));
+        desc->mux_function = function;
         spin_unlock(&desc->lock);
 
         /* Let each pin increase references to this module */
@@ -168,8 +167,7 @@ static int pin_request(struct pinctrl_dev *pctldev,
 out_free_pin:
         if (status) {
                 spin_lock(&desc->lock);
-                desc->mux_requested = false;
-                desc->mux_function[0] = '\0';
+                desc->mux_function = NULL;
                 spin_unlock(&desc->lock);
         }
 out:
@@ -184,8 +182,9 @@ out:
  * pin_free() - release a single muxed in pin so something else can be muxed
  * @pctldev: pin controller device handling this pin
  * @pin: the pin to free
+ * @free_func: whether to free the pin's assigned function name string
  */
-static void pin_free(struct pinctrl_dev *pctldev, int pin)
+static void pin_free(struct pinctrl_dev *pctldev, int pin, int free_func)
 {
         const struct pinmux_ops *ops = pctldev->desc->pmxops;
         struct pin_desc *desc;
@@ -201,8 +200,9 @@ static void pin_free(struct pinctrl_dev *pctldev, int pin)
                 ops->free(pctldev, pin);
 
         spin_lock(&desc->lock);
-        desc->mux_requested = false;
-        desc->mux_function[0] = '\0';
+        if (free_func)
+                kfree(desc->mux_function);
+        desc->mux_function = NULL;
         spin_unlock(&desc->lock);
         module_put(pctldev->owner);
 }
@@ -214,6 +214,7 @@ static void pin_free(struct pinctrl_dev *pctldev, int pin)
 int pinmux_request_gpio(unsigned gpio)
 {
         char gpiostr[16];
+        const char *function;
         struct pinctrl_dev *pctldev;
         struct pinctrl_gpio_range *range;
         int ret;
@@ -229,7 +230,15 @@ int pinmux_request_gpio(unsigned gpio)
         /* Conjure some name stating what chip and pin this is taken by */
         snprintf(gpiostr, 15, "%s:%d", range->name, gpio);
 
-        return pin_request(pctldev, pin, gpiostr, true, range);
+        function = kstrdup(gpiostr, GFP_KERNEL);
+        if (!function)
+                return -EINVAL;
+
+        ret = pin_request(pctldev, pin, function, true, range);
+        if (ret < 0)
+                kfree(function);
+
+        return ret;
 }
 EXPORT_SYMBOL_GPL(pinmux_request_gpio);
 
@@ -251,7 +260,7 @@ void pinmux_free_gpio(unsigned gpio)
         /* Convert to the pin controllers number space */
         pin = gpio - range->base;
 
-        pin_free(pctldev, pin);
+        pin_free(pctldev, pin, true);
 }
 EXPORT_SYMBOL_GPL(pinmux_free_gpio);
 
@@ -351,7 +360,7 @@ static int acquire_pins(struct pinctrl_dev *pctldev,
                         /* On error release all taken pins */
                         i--; /* this pin just failed */
                         for (; i >= 0; i--)
-                                pin_free(pctldev, pins[i]);
+                                pin_free(pctldev, pins[i], false);
                         return -ENODEV;
                 }
         }
@@ -381,7 +390,7 @@ static void release_pins(struct pinctrl_dev *pctldev,
                 return;
         }
         for (i = 0; i < num_pins; i++)
-                pin_free(pctldev, pins[i]);
+                pin_free(pctldev, pins[i], false);
 }
 
 /**
@@ -1013,7 +1022,8 @@ static int pinmux_pins_show(struct seq_file *s, void *what)
 
                 seq_printf(s, "pin %d (%s): %s\n", pin,
                            desc->name ? desc->name : "unnamed",
-                           desc->mux_requested ? desc->mux_function : "UNCLAIMED");
+                           desc->mux_function ? desc->mux_function
+                                              : "UNCLAIMED");
         }
 
         return 0;