gpiolib: add support for changing value polarity in sysfs

Drivers may use gpiolib sysfs as part of their public user space interface. The GPIO number and polarity might change from board to board. The gpio_export_link() call can be used to hide the GPIO number from user space. Add support for also hiding the GPIO line polarity changes from user space. Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

gpiolib: add support for changing value polarity in sysfs
Drivers may use gpiolib sysfs as part of their public user space interface. The GPIO number and polarity might change from board to board. The gpio_export_link() call can be used to hide the GPIO number from user space. Add support for also hiding the GPIO line polarity changes from user space. Signed-off-by: Jani Nikula <ext-jani.1.nikula@nokia.com> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Jani Nikula · Linus Torvalds
1 parent 35570ac603
Showing 4 changed files with 176 additions and 12 deletions Side-by-side Diff
Documentation/gpio.txt
drivers/gpio/gpiolib.c
include/asm-generic/gpio.h
include/linux/gpio.h
@@ -531,6 +531,13 @@
 		This file exists only if the pin can be configured as an
 		interrupt generating input pin.
  
+	"active_low" ... reads as either 0 (false) or 1 (true).  Write
+		any nonzero value to invert the value attribute both
+		for reading and writing.  Existing and subsequent
+		poll(2) support configuration via the edge attribute
+		for "rising" and "falling" edges will follow this
+		setting.
+
 GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
 controller implementing GPIOs starting at #42) and have the following
 read-only attributes:
@@ -566,6 +573,8 @@
 	int gpio_export_link(struct device *dev, const char *name,
 		unsigned gpio)
  
+	/* change the polarity of a GPIO node in sysfs */
+	int gpio_sysfs_set_active_low(unsigned gpio, int value);
  
 After a kernel driver requests a GPIO, it may only be made available in
 the sysfs interface by gpio_export().  The driver can control whether the
@@ -580,4 +589,10 @@
 symlinks from elsewhere in sysfs to the GPIO sysfs node.  Drivers can
 use this to provide the interface under their own device in sysfs with
 a descriptive name.
+
+Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
+differences between boards from user space.  This only affects the
+sysfs interface.  Polarity change can be done both before and after
+gpio_export(), and previously enabled poll(2) support for either
+rising or falling edge will be reconfigured to follow this setting.
@@ -53,6 +53,7 @@
 #define FLAG_SYSFS	4	/* exported via /sys/class/gpio/control */
 #define FLAG_TRIG_FALL	5	/* trigger on falling edge */
 #define FLAG_TRIG_RISE	6	/* trigger on rising edge */
+#define FLAG_ACTIVE_LOW	7	/* sysfs value has active low */
  
 #define PDESC_ID_SHIFT	16	/* add new flags before this one */
  
@@ -210,6 +211,11 @@
  *      * configures behavior of poll(2) on /value
  *      * available only if pin can generate IRQs on input
  *      * is read/write as "none", "falling", "rising", or "both"
+ *   /active_low
+ *      * configures polarity of /value
+ *      * is read/write as zero/nonzero
+ *      * also affects existing and subsequent "falling" and "rising"
+ *        /edge configuration
  */
  
 static ssize_t gpio_direction_show(struct device *dev,
@@ -255,7 +261,7 @@
 	return status ? : size;
 }
  
-static const DEVICE_ATTR(direction, 0644,
+static /* const */ DEVICE_ATTR(direction, 0644,
 		gpio_direction_show, gpio_direction_store);
  
 static ssize_t gpio_value_show(struct device *dev,
  
  
@@ -267,11 +273,18 @@
  
 	mutex_lock(&sysfs_lock);
  
-	if (!test_bit(FLAG_EXPORT, &desc->flags))
+	if (!test_bit(FLAG_EXPORT, &desc->flags)) {
 		status = -EIO;
-	else
-		status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio));
+	} else {
+		int value;
  
+		value = !!gpio_get_value_cansleep(gpio);
+		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+			value = !value;
+
+		status = sprintf(buf, "%d\n", value);
+	}
+
 	mutex_unlock(&sysfs_lock);
 	return status;
 }
@@ -294,6 +307,8 @@
  
 		status = strict_strtol(buf, 0, &value);
 		if (status == 0) {
+			if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+				value = !value;
 			gpio_set_value_cansleep(gpio, value != 0);
 			status = size;
 		}
@@ -303,7 +318,7 @@
 	return status;
 }
  
-static /*const*/ DEVICE_ATTR(value, 0644,
+static const DEVICE_ATTR(value, 0644,
 		gpio_value_show, gpio_value_store);
  
 static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
  
@@ -352,9 +367,11 @@
  
 	irq_flags = IRQF_SHARED;
 	if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
-		irq_flags |= IRQF_TRIGGER_FALLING;
+		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+			IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
 	if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
-		irq_flags |= IRQF_TRIGGER_RISING;
+		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
  
 	if (!pdesc) {
 		pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
  
  
@@ -475,9 +492,79 @@
  
 static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
  
+static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
+				int value)
+{
+	int			status = 0;
+
+	if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
+		return 0;
+
+	if (value)
+		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
+	else
+		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
+
+	/* reconfigure poll(2) support if enabled on one edge only */
+	if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
+				!!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
+		unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;
+
+		gpio_setup_irq(desc, dev, 0);
+		status = gpio_setup_irq(desc, dev, trigger_flags);
+	}
+
+	return status;
+}
+
+static ssize_t gpio_active_low_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	const struct gpio_desc	*desc = dev_get_drvdata(dev);
+	ssize_t			status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(FLAG_EXPORT, &desc->flags))
+		status = -EIO;
+	else
+		status = sprintf(buf, "%d\n",
+				!!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+static ssize_t gpio_active_low_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct gpio_desc	*desc = dev_get_drvdata(dev);
+	ssize_t			status;
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(FLAG_EXPORT, &desc->flags)) {
+		status = -EIO;
+	} else {
+		long		value;
+
+		status = strict_strtol(buf, 0, &value);
+		if (status == 0)
+			status = sysfs_set_active_low(desc, dev, value != 0);
+	}
+
+	mutex_unlock(&sysfs_lock);
+
+	return status ? : size;
+}
+
+static const DEVICE_ATTR(active_low, 0644,
+		gpio_active_low_show, gpio_active_low_store);
+
 static const struct attribute *gpio_attrs[] = {
-	&dev_attr_direction.attr,
 	&dev_attr_value.attr,
+	&dev_attr_active_low.attr,
 	NULL,
 };
  
  
  
@@ -662,12 +749,12 @@
 		dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
 				desc, ioname ? ioname : "gpio%d", gpio);
 		if (!IS_ERR(dev)) {
-			if (direction_may_change)
-				status = sysfs_create_group(&dev->kobj,
+			status = sysfs_create_group(&dev->kobj,
 						&gpio_attr_group);
-			else
+
+			if (!status && direction_may_change)
 				status = device_create_file(dev,
-						&dev_attr_value);
+						&dev_attr_direction);
  
 			if (!status && gpio_to_irq(gpio) >= 0
 					&& (direction_may_change
  
@@ -744,7 +831,56 @@
 }
 EXPORT_SYMBOL_GPL(gpio_export_link);
  
+
 /**
+ * gpio_sysfs_set_active_low - set the polarity of gpio sysfs value
+ * @gpio: gpio to change
+ * @value: non-zero to use active low, i.e. inverted values
+ *
+ * Set the polarity of /sys/class/gpio/gpioN/value sysfs attribute.
+ * The GPIO does not have to be exported yet.  If poll(2) support has
+ * been enabled for either rising or falling edge, it will be
+ * reconfigured to follow the new polarity.
+ *
+ * Returns zero on success, else an error.
+ */
+int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+	struct gpio_desc	*desc;
+	struct device		*dev = NULL;
+	int			status = -EINVAL;
+
+	if (!gpio_is_valid(gpio))
+		goto done;
+
+	mutex_lock(&sysfs_lock);
+
+	desc = &gpio_desc[gpio];
+
+	if (test_bit(FLAG_EXPORT, &desc->flags)) {
+		struct device *dev;
+
+		dev = class_find_device(&gpio_class, NULL, desc, match_export);
+		if (dev == NULL) {
+			status = -ENODEV;
+			goto unlock;
+		}
+	}
+
+	status = sysfs_set_active_low(desc, dev, value);
+
+unlock:
+	mutex_unlock(&sysfs_lock);
+
+done:
+	if (status)
+		pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(gpio_sysfs_set_active_low);
+
+/**
  * gpio_unexport - reverse effect of gpio_export()
  * @gpio: gpio to make unavailable
  *
@@ -1094,6 +1230,7 @@
 		}
 		desc_set_label(desc, NULL);
 		module_put(desc->chip->owner);
+		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
 		clear_bit(FLAG_REQUESTED, &desc->flags);
 	} else
 		WARN_ON(extra_checks);
@@ -145,6 +145,7 @@
 extern int gpio_export(unsigned gpio, bool direction_may_change);
 extern int gpio_export_link(struct device *dev, const char *name,
 			unsigned gpio);
+extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
 extern void gpio_unexport(unsigned gpio);
  
 #endif	/* CONFIG_GPIO_SYSFS */
@@ -193,6 +194,11 @@
  
 static inline int gpio_export_link(struct device *dev, const char *name,
 				unsigned gpio)
+{
+	return -ENOSYS;
+}
+
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
 {
 	return -ENOSYS;
 }
@@ -99,6 +99,12 @@
 	return -EINVAL;
 }
  
+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
+{
+	/* GPIO can never have been requested */
+	WARN_ON(1);
+	return -EINVAL;
+}
  
 static inline void gpio_unexport(unsigned gpio)
 {
...	...	@@ -531,6 +531,13 @@
531	531	This file exists only if the pin can be configured as an
532	532	interrupt generating input pin.
533	533
	534	+ "active_low" ... reads as either 0 (false) or 1 (true). Write
	535	+ any nonzero value to invert the value attribute both
	536	+ for reading and writing. Existing and subsequent
	537	+ poll(2) support configuration via the edge attribute
	538	+ for "rising" and "falling" edges will follow this
	539	+ setting.
	540	+
534	541	GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
535	542	controller implementing GPIOs starting at #42) and have the following
536	543	read-only attributes:
...	...	@@ -566,6 +573,8 @@
566	573	int gpio_export_link(struct device dev, const char name,
567	574	unsigned gpio)
568	575
	576	+ /* change the polarity of a GPIO node in sysfs */
	577	+ int gpio_sysfs_set_active_low(unsigned gpio, int value);
569	578
570	579	After a kernel driver requests a GPIO, it may only be made available in
571	580	the sysfs interface by gpio_export(). The driver can control whether the
...	...	@@ -580,4 +589,10 @@
580	589	symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
581	590	use this to provide the interface under their own device in sysfs with
582	591	a descriptive name.
	592	+
	593	+Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
	594	+differences between boards from user space. This only affects the
	595	+sysfs interface. Polarity change can be done both before and after
	596	+gpio_export(), and previously enabled poll(2) support for either
	597	+rising or falling edge will be reconfigured to follow this setting.
...	...	@@ -53,6 +53,7 @@
53	53	#define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
54	54	#define FLAG_TRIG_FALL 5 /* trigger on falling edge */
55	55	#define FLAG_TRIG_RISE 6 /* trigger on rising edge */
	56	+#define FLAG_ACTIVE_LOW 7 /* sysfs value has active low */
56	57
57	58	#define PDESC_ID_SHIFT 16 /* add new flags before this one */
58	59
...	...	@@ -210,6 +211,11 @@
210	211	* * configures behavior of poll(2) on /value
211	212	* * available only if pin can generate IRQs on input
212	213	* * is read/write as "none", "falling", "rising", or "both"
	214	+ * /active_low
	215	+ * * configures polarity of /value
	216	+ * * is read/write as zero/nonzero
	217	+ * * also affects existing and subsequent "falling" and "rising"
	218	+ * /edge configuration
213	219	*/
214	220
215	221	static ssize_t gpio_direction_show(struct device *dev,
...	...	@@ -255,7 +261,7 @@
255	261	return status ? : size;
256	262	}
257	263
258		-static const DEVICE_ATTR(direction, 0644,
	264	+static /* const */ DEVICE_ATTR(direction, 0644,
259	265	gpio_direction_show, gpio_direction_store);
260	266
261	267	static ssize_t gpio_value_show(struct device *dev,
262	268
263	269
...	...	@@ -267,11 +273,18 @@
267	273
268	274	mutex_lock(&sysfs_lock);
269	275
270		- if (!test_bit(FLAG_EXPORT, &desc->flags))
	276	+ if (!test_bit(FLAG_EXPORT, &desc->flags)) {
271	277	status = -EIO;
272		- else
273		- status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio));
	278	+ } else {
	279	+ int value;
274	280
	281	+ value = !!gpio_get_value_cansleep(gpio);
	282	+ if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
	283	+ value = !value;
	284	+
	285	+ status = sprintf(buf, "%d\n", value);
	286	+ }
	287	+
275	288	mutex_unlock(&sysfs_lock);
276	289	return status;
277	290	}
...	...	@@ -294,6 +307,8 @@
294	307
295	308	status = strict_strtol(buf, 0, &value);
296	309	if (status == 0) {
	310	+ if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
	311	+ value = !value;
297	312	gpio_set_value_cansleep(gpio, value != 0);
298	313	status = size;
299	314	}
...	...	@@ -303,7 +318,7 @@
303	318	return status;
304	319	}
305	320
306		-static /const/ DEVICE_ATTR(value, 0644,
	321	+static const DEVICE_ATTR(value, 0644,
307	322	gpio_value_show, gpio_value_store);
308	323
309	324	static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
310	325
...	...	@@ -352,9 +367,11 @@
352	367
353	368	irq_flags = IRQF_SHARED;
354	369	if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
355		- irq_flags \|= IRQF_TRIGGER_FALLING;
	370	+ irq_flags \|= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
	371	+ IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
356	372	if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
357		- irq_flags \|= IRQF_TRIGGER_RISING;
	373	+ irq_flags \|= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
	374	+ IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
358	375
359	376	if (!pdesc) {
360	377	pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
361	378
362	379
...	...	@@ -475,9 +492,79 @@
475	492
476	493	static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
477	494
	495	+static int sysfs_set_active_low(struct gpio_desc desc, struct device dev,
	496	+ int value)
	497	+{
	498	+ int status = 0;
	499	+
	500	+ if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
	501	+ return 0;
	502	+
	503	+ if (value)
	504	+ set_bit(FLAG_ACTIVE_LOW, &desc->flags);
	505	+ else
	506	+ clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
	507	+
	508	+ /* reconfigure poll(2) support if enabled on one edge only */
	509	+ if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
	510	+ !!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
	511	+ unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;
	512	+
	513	+ gpio_setup_irq(desc, dev, 0);
	514	+ status = gpio_setup_irq(desc, dev, trigger_flags);
	515	+ }
	516	+
	517	+ return status;
	518	+}
	519	+
	520	+static ssize_t gpio_active_low_show(struct device *dev,
	521	+ struct device_attribute attr, char buf)
	522	+{
	523	+ const struct gpio_desc *desc = dev_get_drvdata(dev);
	524	+ ssize_t status;
	525	+
	526	+ mutex_lock(&sysfs_lock);
	527	+
	528	+ if (!test_bit(FLAG_EXPORT, &desc->flags))
	529	+ status = -EIO;
	530	+ else
	531	+ status = sprintf(buf, "%d\n",
	532	+ !!test_bit(FLAG_ACTIVE_LOW, &desc->flags));
	533	+
	534	+ mutex_unlock(&sysfs_lock);
	535	+
	536	+ return status;
	537	+}
	538	+
	539	+static ssize_t gpio_active_low_store(struct device *dev,
	540	+ struct device_attribute attr, const char buf, size_t size)
	541	+{
	542	+ struct gpio_desc *desc = dev_get_drvdata(dev);
	543	+ ssize_t status;
	544	+
	545	+ mutex_lock(&sysfs_lock);
	546	+
	547	+ if (!test_bit(FLAG_EXPORT, &desc->flags)) {
	548	+ status = -EIO;
	549	+ } else {
	550	+ long value;
	551	+
	552	+ status = strict_strtol(buf, 0, &value);
	553	+ if (status == 0)
	554	+ status = sysfs_set_active_low(desc, dev, value != 0);
	555	+ }
	556	+
	557	+ mutex_unlock(&sysfs_lock);
	558	+
	559	+ return status ? : size;
	560	+}
	561	+
	562	+static const DEVICE_ATTR(active_low, 0644,
	563	+ gpio_active_low_show, gpio_active_low_store);
	564	+
478	565	static const struct attribute *gpio_attrs[] = {
479		- &dev_attr_direction.attr,
480	566	&dev_attr_value.attr,
	567	+ &dev_attr_active_low.attr,
481	568	NULL,
482	569	};
483	570
484	571
485	572
...	...	@@ -662,12 +749,12 @@
662	749	dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
663	750	desc, ioname ? ioname : "gpio%d", gpio);
664	751	if (!IS_ERR(dev)) {
665		- if (direction_may_change)
666		- status = sysfs_create_group(&dev->kobj,
	752	+ status = sysfs_create_group(&dev->kobj,
667	753	&gpio_attr_group);
668		- else
	754	+
	755	+ if (!status && direction_may_change)
669	756	status = device_create_file(dev,
670		- &dev_attr_value);
	757	+ &dev_attr_direction);
671	758
672	759	if (!status && gpio_to_irq(gpio) >= 0
673	760	&& (direction_may_change
674	761
...	...	@@ -744,7 +831,56 @@
744	831	}
745	832	EXPORT_SYMBOL_GPL(gpio_export_link);
746	833
	834	+
747	835	/**
	836	+ * gpio_sysfs_set_active_low - set the polarity of gpio sysfs value
	837	+ * @gpio: gpio to change
	838	+ * @value: non-zero to use active low, i.e. inverted values
	839	+ *
	840	+ * Set the polarity of /sys/class/gpio/gpioN/value sysfs attribute.
	841	+ * The GPIO does not have to be exported yet. If poll(2) support has
	842	+ * been enabled for either rising or falling edge, it will be
	843	+ * reconfigured to follow the new polarity.
	844	+ *
	845	+ * Returns zero on success, else an error.
	846	+ */
	847	+int gpio_sysfs_set_active_low(unsigned gpio, int value)
	848	+{
	849	+ struct gpio_desc *desc;
	850	+ struct device *dev = NULL;
	851	+ int status = -EINVAL;
	852	+
	853	+ if (!gpio_is_valid(gpio))
	854	+ goto done;
	855	+
	856	+ mutex_lock(&sysfs_lock);
	857	+
	858	+ desc = &gpio_desc[gpio];
	859	+
	860	+ if (test_bit(FLAG_EXPORT, &desc->flags)) {
	861	+ struct device *dev;
	862	+
	863	+ dev = class_find_device(&gpio_class, NULL, desc, match_export);
	864	+ if (dev == NULL) {
	865	+ status = -ENODEV;
	866	+ goto unlock;
	867	+ }
	868	+ }
	869	+
	870	+ status = sysfs_set_active_low(desc, dev, value);
	871	+
	872	+unlock:
	873	+ mutex_unlock(&sysfs_lock);
	874	+
	875	+done:
	876	+ if (status)
	877	+ pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
	878	+
	879	+ return status;
	880	+}
	881	+EXPORT_SYMBOL_GPL(gpio_sysfs_set_active_low);
	882	+
	883	+/**
748	884	* gpio_unexport - reverse effect of gpio_export()
749	885	* @gpio: gpio to make unavailable
750	886	*
...	...	@@ -1094,6 +1230,7 @@
1094	1230	}
1095	1231	desc_set_label(desc, NULL);
1096	1232	module_put(desc->chip->owner);
	1233	+ clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
1097	1234	clear_bit(FLAG_REQUESTED, &desc->flags);
1098	1235	} else
1099	1236	WARN_ON(extra_checks);
...	...	@@ -145,6 +145,7 @@
145	145	extern int gpio_export(unsigned gpio, bool direction_may_change);
146	146	extern int gpio_export_link(struct device dev, const char name,
147	147	unsigned gpio);
	148	+extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
148	149	extern void gpio_unexport(unsigned gpio);
149	150
150	151	#endif /* CONFIG_GPIO_SYSFS */
...	...	@@ -193,6 +194,11 @@
193	194
194	195	static inline int gpio_export_link(struct device dev, const char name,
195	196	unsigned gpio)
	197	+{
	198	+ return -ENOSYS;
	199	+}
	200	+
	201	+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
196	202	{
197	203	return -ENOSYS;
198	204	}
...	...	@@ -99,6 +99,12 @@
99	99	return -EINVAL;
100	100	}
101	101
	102	+static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
	103	+{
	104	+ /* GPIO can never have been requested */
	105	+ WARN_ON(1);
	106	+ return -EINVAL;
	107	+}
102	108
103	109	static inline void gpio_unexport(unsigned gpio)
104	110	{