3 files changed, 667 insertions, 0 deletions

diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 369e4fc432e3..c3da03975d58 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -2,3 +2,5 @@
 
 ccflags-$(CONFIG_DEBUG_GPIO)    += -DDEBUG
 
+obj-$(CONFIG_HAVE_GPIO_LIB)     += gpiolib.o
+
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
new file mode 100644
index 000000000000..d8db2f8ee411
--- /dev/null
+++ b/drivers/gpio/gpiolib.c
@@ -0,0 +1,567 @@
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/irq.h>
+#include <linux/spinlock.h>
+
+#include <asm/gpio.h>
+
+
+/* Optional implementation infrastructure for GPIO interfaces.
+ *
+ * Platforms may want to use this if they tend to use very many GPIOs
+ * that aren't part of a System-On-Chip core; or across I2C/SPI/etc.
+ *
+ * When kernel footprint or instruction count is an issue, simpler
+ * implementations may be preferred.  The GPIO programming interface
+ * allows for inlining speed-critical get/set operations for common
+ * cases, so that access to SOC-integrated GPIOs can sometimes cost
+ * only an instruction or two per bit.
+ */
+
+
+/* When debugging, extend minimal trust to callers and platform code.
+ * Also emit diagnostic messages that may help initial bringup, when
+ * board setup or driver bugs are most common.
+ *
+ * Otherwise, minimize overhead in what may be bitbanging codepaths.
+ */
+#ifdef  DEBUG
+#define extra_checks    1
+#else
+#define extra_checks    0
+#endif
+
+/* gpio_lock prevents conflicts during gpio_desc[] table updates.
+ * While any GPIO is requested, its gpio_chip is not removable;
+ * each GPIO's "requested" flag serves as a lock and refcount.
+ */
+static DEFINE_SPINLOCK(gpio_lock);
+
+struct gpio_desc {
+        struct gpio_chip        *chip;
+        unsigned long           flags;
+/* flag symbols are bit numbers */
+#define FLAG_REQUESTED  0
+#define FLAG_IS_OUT     1
+
+#ifdef CONFIG_DEBUG_FS
+        const char              *label;
+#endif
+};
+static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
+
+static inline void desc_set_label(struct gpio_desc *d, const char *label)
+{
+#ifdef CONFIG_DEBUG_FS
+        d->label = label;
+#endif
+}
+
+/* Warn when drivers omit gpio_request() calls -- legal but ill-advised
+ * when setting direction, and otherwise illegal.  Until board setup code
+ * and drivers use explicit requests everywhere (which won't happen when
+ * those calls have no teeth) we can't avoid autorequesting.  This nag
+ * message should motivate switching to explicit requests...
+ */
+static void gpio_ensure_requested(struct gpio_desc *desc)
+{
+        if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
+                pr_warning("GPIO-%d autorequested\n", (int)(desc - gpio_desc));
+                desc_set_label(desc, "[auto]");
+        }
+}
+
+/* caller holds gpio_lock *OR* gpio is marked as requested */
+static inline struct gpio_chip *gpio_to_chip(unsigned gpio)
+{
+        return gpio_desc[gpio].chip;
+}
+
+/**
+ * gpiochip_add() - register a gpio_chip
+ * @chip: the chip to register, with chip->base initialized
+ * Context: potentially before irqs or kmalloc will work
+ *
+ * Returns a negative errno if the chip can't be registered, such as
+ * because the chip->base is invalid or already associated with a
+ * different chip.  Otherwise it returns zero as a success code.
+ */
+int gpiochip_add(struct gpio_chip *chip)
+{
+        unsigned long   flags;
+        int             status = 0;
+        unsigned        id;
+
+        /* NOTE chip->base negative is reserved to mean a request for
+         * dynamic allocation.  We don't currently support that.
+         */
+
+        if (chip->base < 0 || (chip->base  + chip->ngpio) >= ARCH_NR_GPIOS) {
+                status = -EINVAL;
+                goto fail;
+        }
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        /* these GPIO numbers must not be managed by another gpio_chip */
+        for (id = chip->base; id < chip->base + chip->ngpio; id++) {
+                if (gpio_desc[id].chip != NULL) {
+                        status = -EBUSY;
+                        break;
+                }
+        }
+        if (status == 0) {
+                for (id = chip->base; id < chip->base + chip->ngpio; id++) {
+                        gpio_desc[id].chip = chip;
+                        gpio_desc[id].flags = 0;
+                }
+        }
+
+        spin_unlock_irqrestore(&gpio_lock, flags);
+fail:
+        /* failures here can mean systems won't boot... */
+        if (status)
+                pr_err("gpiochip_add: gpios %d..%d (%s) not registered\n",
+                        chip->base, chip->base + chip->ngpio,
+                        chip->label ? : "generic");
+        return status;
+}
+EXPORT_SYMBOL_GPL(gpiochip_add);
+
+/**
+ * gpiochip_remove() - unregister a gpio_chip
+ * @chip: the chip to unregister
+ *
+ * A gpio_chip with any GPIOs still requested may not be removed.
+ */
+int gpiochip_remove(struct gpio_chip *chip)
+{
+        unsigned long   flags;
+        int             status = 0;
+        unsigned        id;
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        for (id = chip->base; id < chip->base + chip->ngpio; id++) {
+                if (test_bit(FLAG_REQUESTED, &gpio_desc[id].flags)) {
+                        status = -EBUSY;
+                        break;
+                }
+        }
+        if (status == 0) {
+                for (id = chip->base; id < chip->base + chip->ngpio; id++)
+                        gpio_desc[id].chip = NULL;
+        }
+
+        spin_unlock_irqrestore(&gpio_lock, flags);
+        return status;
+}
+EXPORT_SYMBOL_GPL(gpiochip_remove);
+
+
+/* These "optional" allocation calls help prevent drivers from stomping
+ * on each other, and help provide better diagnostics in debugfs.
+ * They're called even less than the "set direction" calls.
+ */
+int gpio_request(unsigned gpio, const char *label)
+{
+        struct gpio_desc        *desc;
+        int                     status = -EINVAL;
+        unsigned long           flags;
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        if (gpio >= ARCH_NR_GPIOS)
+                goto done;
+        desc = &gpio_desc[gpio];
+        if (desc->chip == NULL)
+                goto done;
+
+        /* NOTE:  gpio_request() can be called in early boot,
+         * before IRQs are enabled.
+         */
+
+        if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
+                desc_set_label(desc, label ? : "?");
+                status = 0;
+        } else
+                status = -EBUSY;
+
+done:
+        if (status)
+                pr_debug("gpio_request: gpio-%d (%s) status %d\n",
+                        gpio, label ? : "?", status);
+        spin_unlock_irqrestore(&gpio_lock, flags);
+        return status;
+}
+EXPORT_SYMBOL_GPL(gpio_request);
+
+void gpio_free(unsigned gpio)
+{
+        unsigned long           flags;
+        struct gpio_desc        *desc;
+
+        if (gpio >= ARCH_NR_GPIOS) {
+                WARN_ON(extra_checks);
+                return;
+        }
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        desc = &gpio_desc[gpio];
+        if (desc->chip && test_and_clear_bit(FLAG_REQUESTED, &desc->flags))
+                desc_set_label(desc, NULL);
+        else
+                WARN_ON(extra_checks);
+
+        spin_unlock_irqrestore(&gpio_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gpio_free);
+
+
+/**
+ * gpiochip_is_requested - return string iff signal was requested
+ * @chip: controller managing the signal
+ * @offset: of signal within controller's 0..(ngpio - 1) range
+ *
+ * Returns NULL if the GPIO is not currently requested, else a string.
+ * If debugfs support is enabled, the string returned is the label passed
+ * to gpio_request(); otherwise it is a meaningless constant.
+ *
+ * This function is for use by GPIO controller drivers.  The label can
+ * help with diagnostics, and knowing that the signal is used as a GPIO
+ * can help avoid accidentally multiplexing it to another controller.
+ */
+const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset)
+{
+        unsigned gpio = chip->base + offset;
+
+        if (gpio >= ARCH_NR_GPIOS || gpio_desc[gpio].chip != chip)
+                return NULL;
+        if (test_bit(FLAG_REQUESTED, &gpio_desc[gpio].flags) == 0)
+                return NULL;
+#ifdef CONFIG_DEBUG_FS
+        return gpio_desc[gpio].label;
+#else
+        return "?";
+#endif
+}
+EXPORT_SYMBOL_GPL(gpiochip_is_requested);
+
+
+/* Drivers MUST set GPIO direction before making get/set calls.  In
+ * some cases this is done in early boot, before IRQs are enabled.
+ *
+ * As a rule these aren't called more than once (except for drivers
+ * using the open-drain emulation idiom) so these are natural places
+ * to accumulate extra debugging checks.  Note that we can't (yet)
+ * rely on gpio_request() having been called beforehand.
+ */
+
+int gpio_direction_input(unsigned gpio)
+{
+        unsigned long           flags;
+        struct gpio_chip        *chip;
+        struct gpio_desc        *desc = &gpio_desc[gpio];
+        int                     status = -EINVAL;
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        if (gpio >= ARCH_NR_GPIOS)
+                goto fail;
+        chip = desc->chip;
+        if (!chip || !chip->get || !chip->direction_input)
+                goto fail;
+        gpio -= chip->base;
+        if (gpio >= chip->ngpio)
+                goto fail;
+        gpio_ensure_requested(desc);
+
+        /* now we know the gpio is valid and chip won't vanish */
+
+        spin_unlock_irqrestore(&gpio_lock, flags);
+
+        might_sleep_if(extra_checks && chip->can_sleep);
+
+        status = chip->direction_input(chip, gpio);
+        if (status == 0)
+                clear_bit(FLAG_IS_OUT, &desc->flags);
+        return status;
+fail:
+        spin_unlock_irqrestore(&gpio_lock, flags);
+        if (status)
+                pr_debug("%s: gpio-%d status %d\n",
+                        __FUNCTION__, gpio, status);
+        return status;
+}
+EXPORT_SYMBOL_GPL(gpio_direction_input);
+
+int gpio_direction_output(unsigned gpio, int value)
+{
+        unsigned long           flags;
+        struct gpio_chip        *chip;
+        struct gpio_desc        *desc = &gpio_desc[gpio];
+        int                     status = -EINVAL;
+
+        spin_lock_irqsave(&gpio_lock, flags);
+
+        if (gpio >= ARCH_NR_GPIOS)
+                goto fail;
+        chip = desc->chip;
+        if (!chip || !chip->set || !chip->direction_output)
+                goto fail;
+        gpio -= chip->base;
+        if (gpio >= chip->ngpio)
+                goto fail;
+        gpio_ensure_requested(desc);
+
+        /* now we know the gpio is valid and chip won't vanish */
+
+        spin_unlock_irqrestore(&gpio_lock, flags);
+
+        might_sleep_if(extra_checks && chip->can_sleep);
+
+        status = chip->direction_output(chip, gpio, value);
+        if (status == 0)
+                set_bit(FLAG_IS_OUT, &desc->flags);
+        return status;
+fail:
+        spin_unlock_irqrestore(&gpio_lock, flags);
+        if (status)
+                pr_debug("%s: gpio-%d status %d\n",
+                        __FUNCTION__, gpio, status);
+        return status;
+}
+EXPORT_SYMBOL_GPL(gpio_direction_output);
+
+
+/* I/O calls are only valid after configuration completed; the relevant
+ * "is this a valid GPIO" error checks should already have been done.
+ *
+ * "Get" operations are often inlinable as reading a pin value register,
+ * and masking the relevant bit in that register.
+ *
+ * When "set" operations are inlinable, they involve writing that mask to
+ * one register to set a low value, or a different register to set it high.
+ * Otherwise locking is needed, so there may be little value to inlining.
+ *
+ *------------------------------------------------------------------------
+ *
+ * IMPORTANT!!!  The hot paths -- get/set value -- assume that callers
+ * have requested the GPIO.  That can include implicit requesting by
+ * a direction setting call.  Marking a gpio as requested locks its chip
+ * in memory, guaranteeing that these table lookups need no more locking
+ * and that gpiochip_remove() will fail.
+ *
+ * REVISIT when debugging, consider adding some instrumentation to ensure
+ * that the GPIO was actually requested.
+ */
+
+/**
+ * __gpio_get_value() - return a gpio's value
+ * @gpio: gpio whose value will be returned
+ * Context: any
+ *
+ * This is used directly or indirectly to implement gpio_get_value().
+ * It returns the zero or nonzero value provided by the associated
+ * gpio_chip.get() method; or zero if no such method is provided.
+ */
+int __gpio_get_value(unsigned gpio)
+{
+        struct gpio_chip        *chip;
+
+        chip = gpio_to_chip(gpio);
+        WARN_ON(extra_checks && chip->can_sleep);
+        return chip->get ? chip->get(chip, gpio - chip->base) : 0;
+}
+EXPORT_SYMBOL_GPL(__gpio_get_value);
+
+/**
+ * __gpio_set_value() - assign a gpio's value
+ * @gpio: gpio whose value will be assigned
+ * @value: value to assign
+ * Context: any
+ *
+ * This is used directly or indirectly to implement gpio_set_value().
+ * It invokes the associated gpio_chip.set() method.
+ */
+void __gpio_set_value(unsigned gpio, int value)
+{
+        struct gpio_chip        *chip;
+
+        chip = gpio_to_chip(gpio);
+        WARN_ON(extra_checks && chip->can_sleep);
+        chip->set(chip, gpio - chip->base, value);
+}
+EXPORT_SYMBOL_GPL(__gpio_set_value);
+
+/**
+ * __gpio_cansleep() - report whether gpio value access will sleep
+ * @gpio: gpio in question
+ * Context: any
+ *
+ * This is used directly or indirectly to implement gpio_cansleep().  It
+ * returns nonzero if access reading or writing the GPIO value can sleep.
+ */
+int __gpio_cansleep(unsigned gpio)
+{
+        struct gpio_chip        *chip;
+
+        /* only call this on GPIOs that are valid! */
+        chip = gpio_to_chip(gpio);
+
+        return chip->can_sleep;
+}
+EXPORT_SYMBOL_GPL(__gpio_cansleep);
+
+
+
+/* There's no value in making it easy to inline GPIO calls that may sleep.
+ * Common examples include ones connected to I2C or SPI chips.
+ */
+
+int gpio_get_value_cansleep(unsigned gpio)
+{
+        struct gpio_chip        *chip;
+
+        might_sleep_if(extra_checks);
+        chip = gpio_to_chip(gpio);
+        return chip->get(chip, gpio - chip->base);
+}
+EXPORT_SYMBOL_GPL(gpio_get_value_cansleep);
+
+void gpio_set_value_cansleep(unsigned gpio, int value)
+{
+        struct gpio_chip        *chip;
+
+        might_sleep_if(extra_checks);
+        chip = gpio_to_chip(gpio);
+        chip->set(chip, gpio - chip->base, value);
+}
+EXPORT_SYMBOL_GPL(gpio_set_value_cansleep);
+
+
+#ifdef CONFIG_DEBUG_FS
+
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+
+static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
+{
+        unsigned                i;
+        unsigned                gpio = chip->base;
+        struct gpio_desc        *gdesc = &gpio_desc[gpio];
+        int                     is_out;
+
+        for (i = 0; i < chip->ngpio; i++, gpio++, gdesc++) {
+                if (!test_bit(FLAG_REQUESTED, &gdesc->flags))
+                        continue;
+
+                is_out = test_bit(FLAG_IS_OUT, &gdesc->flags);
+                seq_printf(s, " gpio-%-3d (%-12s) %s %s",
+                        gpio, gdesc->label,
+                        is_out ? "out" : "in ",
+                        chip->get
+                                ? (chip->get(chip, i) ? "hi" : "lo")
+                                : "?  ");
+
+                if (!is_out) {
+                        int             irq = gpio_to_irq(gpio);
+                        struct irq_desc *desc = irq_desc + irq;
+
+                        /* This races with request_irq(), set_irq_type(),
+                         * and set_irq_wake() ... but those are "rare".
+                         *
+                         * More significantly, trigger type flags aren't
+                         * currently maintained by genirq.
+                         */
+                        if (irq >= 0 && desc->action) {
+                                char *trigger;
+
+                                switch (desc->status & IRQ_TYPE_SENSE_MASK) {
+                                case IRQ_TYPE_NONE:
+                                        trigger = "(default)";
+                                        break;
+                                case IRQ_TYPE_EDGE_FALLING:
+                                        trigger = "edge-falling";
+                                        break;
+                                case IRQ_TYPE_EDGE_RISING:
+                                        trigger = "edge-rising";
+                                        break;
+                                case IRQ_TYPE_EDGE_BOTH:
+                                        trigger = "edge-both";
+                                        break;
+                                case IRQ_TYPE_LEVEL_HIGH:
+                                        trigger = "level-high";
+                                        break;
+                                case IRQ_TYPE_LEVEL_LOW:
+                                        trigger = "level-low";
+                                        break;
+                                default:
+                                        trigger = "?trigger?";
+                                        break;
+                                }
+
+                                seq_printf(s, " irq-%d %s%s",
+                                        irq, trigger,
+                                        (desc->status & IRQ_WAKEUP)
+                                                ? " wakeup" : "");
+                        }
+                }
+
+                seq_printf(s, "\n");
+        }
+}
+
+static int gpiolib_show(struct seq_file *s, void *unused)
+{
+        struct gpio_chip        *chip = NULL;
+        unsigned                gpio;
+        int                     started = 0;
+
+        /* REVISIT this isn't locked against gpio_chip removal ... */
+
+        for (gpio = 0; gpio < ARCH_NR_GPIOS; gpio++) {
+                if (chip == gpio_desc[gpio].chip)
+                        continue;
+                chip = gpio_desc[gpio].chip;
+                if (!chip)
+                        continue;
+
+                seq_printf(s, "%sGPIOs %d-%d, %s%s:\n",
+                                started ? "\n" : "",
+                                chip->base, chip->base + chip->ngpio - 1,
+                                chip->label ? : "generic",
+                                chip->can_sleep ? ", can sleep" : "");
+                started = 1;
+                if (chip->dbg_show)
+                        chip->dbg_show(s, chip);
+                else
+                        gpiolib_dbg_show(s, chip);
+        }
+        return 0;
+}
+
+static int gpiolib_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, gpiolib_show, NULL);
+}
+
+static struct file_operations gpiolib_operations = {
+        .open           = gpiolib_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
+static int __init gpiolib_debugfs_init(void)
+{
+        /* /sys/kernel/debug/gpio */
+        (void) debugfs_create_file("gpio", S_IFREG | S_IRUGO,
+                                NULL, NULL, &gpiolib_operations);
+        return 0;
+}
+subsys_initcall(gpiolib_debugfs_init);
+
+#endif  /* DEBUG_FS */
diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index 2d0aab1d8611..f29a502f4a6c 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -1,6 +1,102 @@
 #ifndef _ASM_GENERIC_GPIO_H
 #define _ASM_GENERIC_GPIO_H
 
+#ifdef CONFIG_HAVE_GPIO_LIB
+
+/* Platforms may implement their GPIO interface with library code,
+ * at a small performance cost for non-inlined operations and some
+ * extra memory (for code and for per-GPIO table entries).
+ *
+ * While the GPIO programming interface defines valid GPIO numbers
+ * to be in the range 0..MAX_INT, this library restricts them to the
+ * smaller range 0..ARCH_NR_GPIOS.
+ */
+
+#ifndef ARCH_NR_GPIOS
+#define ARCH_NR_GPIOS           256
+#endif
+
+struct seq_file;
+
+/**
+ * struct gpio_chip - abstract a GPIO controller
+ * @label: for diagnostics
+ * @direction_input: configures signal "offset" as input, or returns error
+ * @get: returns value for signal "offset"; for output signals this
+ *      returns either the value actually sensed, or zero
+ * @direction_output: configures signal "offset" as output, or returns error
+ * @set: assigns output value for signal "offset"
+ * @dbg_show: optional routine to show contents in debugfs; default code
+ *      will be used when this is omitted, but custom code can show extra
+ *      state (such as pullup/pulldown configuration).
+ * @base: identifies the first GPIO number handled by this chip; or, if
+ *      negative during registration, requests dynamic ID allocation.
+ * @ngpio: the number of GPIOs handled by this controller; the last GPIO
+ *      handled is (base + ngpio - 1).
+ * @can_sleep: flag must be set iff get()/set() methods sleep, as they
+ *      must while accessing GPIO expander chips over I2C or SPI
+ *
+ * A gpio_chip can help platforms abstract various sources of GPIOs so
+ * they can all be accessed through a common programing interface.
+ * Example sources would be SOC controllers, FPGAs, multifunction
+ * chips, dedicated GPIO expanders, and so on.
+ *
+ * Each chip controls a number of signals, identified in method calls
+ * by "offset" values in the range 0..(@ngpio - 1).  When those signals
+ * are referenced through calls like gpio_get_value(gpio), the offset
+ * is calculated by subtracting @base from the gpio number.
+ */
+struct gpio_chip {
+        char                    *label;
+
+        int                     (*direction_input)(struct gpio_chip *chip,
+                                                unsigned offset);
+        int                     (*get)(struct gpio_chip *chip,
+                                                unsigned offset);
+        int                     (*direction_output)(struct gpio_chip *chip,
+                                                unsigned offset, int value);
+        void                    (*set)(struct gpio_chip *chip,
+                                                unsigned offset, int value);
+        void                    (*dbg_show)(struct seq_file *s,
+                                                struct gpio_chip *chip);
+        int                     base;
+        u16                     ngpio;
+        unsigned                can_sleep:1;
+};
+
+extern const char *gpiochip_is_requested(struct gpio_chip *chip,
+                        unsigned offset);
+
+/* add/remove chips */
+extern int gpiochip_add(struct gpio_chip *chip);
+extern int __must_check gpiochip_remove(struct gpio_chip *chip);
+
+
+/* Always use the library code for GPIO management calls,
+ * or when sleeping may be involved.
+ */
+extern int gpio_request(unsigned gpio, const char *label);
+extern void gpio_free(unsigned gpio);
+
+extern int gpio_direction_input(unsigned gpio);
+extern int gpio_direction_output(unsigned gpio, int value);
+
+extern int gpio_get_value_cansleep(unsigned gpio);
+extern void gpio_set_value_cansleep(unsigned gpio, int value);
+
+
+/* A platform's <asm/gpio.h> code may want to inline the I/O calls when
+ * the GPIO is constant and refers to some always-present controller,
+ * giving direct access to chip registers and tight bitbanging loops.
+ */
+extern int __gpio_get_value(unsigned gpio);
+extern void __gpio_set_value(unsigned gpio, int value);
+
+extern int __gpio_cansleep(unsigned gpio);
+
+
+#else
+
 /* platforms that don't directly support access to GPIOs through I2C, SPI,
  * or other blocking infrastructure can use these wrappers.
  */
@@ -22,4 +118,6 @@ static inline void gpio_set_value_cansleep(unsigned gpio, int value)
         gpio_set_value(gpio, value);
 }
 
+#endif
+
 #endif /* _ASM_GENERIC_GPIO_H */