gpio: store reflect the label to userspace

The gpio_chip label is useful for userspace to understand what
kind of GPIO chip it is dealing with. Let's store a copy of this
label in the gpio_device, add it to the struct passed to userspace
for GPIO_GET_CHIPINFO_IOCTL and modify lsgpio to show it.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -342,6 +342,9 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		strncpy(chipinfo.name, dev_name(&gdev->dev),
 			sizeof(chipinfo.name));
 		chipinfo.name[sizeof(chipinfo.name)-1] = '\0';
+		strncpy(chipinfo.label, gdev->label,
+			sizeof(chipinfo.label));
+		chipinfo.label[sizeof(chipinfo.label)-1] = '\0';
 		chipinfo.lines = gdev->ngpio;
 		if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
 			return -EFAULT;
@@ -479,6 +482,16 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
 		status = -EINVAL;
 		goto err_free_gdev;
 	}
+
+	if (chip->label)
+		gdev->label = devm_kstrdup(&gdev->dev, chip->label, GFP_KERNEL);
+	else
+		gdev->label = devm_kstrdup(&gdev->dev, "unknown", GFP_KERNEL);
+	if (!gdev->label) {
+		status = -ENOMEM;
+		goto err_free_gdev;
+	}
+
 	gdev->ngpio = chip->ngpio;
 	gdev->data = data;
 

drivers/gpio/gpiolib.h

@@ -37,6 +37,8 @@ struct acpi_device;
  * of the @descs array.
  * @base: GPIO base in the DEPRECATED global Linux GPIO numberspace, assigned
  * at device creation time.
+ * @label: a descriptive name for the GPIO device, such as the part number
+ * or name of the IP component in a System on Chip.
  * @data: per-instance data assigned by the driver
  * @list: links gpio_device:s together for traversal
  *
@@ -55,6 +57,7 @@ struct gpio_device {
 	struct gpio_desc	*descs;
 	int			base;
 	u16			ngpio;
+	char			*label;
 	void			*data;
 	struct list_head        list;
 

include/linux/gpio/driver.h

@@ -21,7 +21,8 @@ struct gpio_device;
 
 /**
  * struct gpio_chip - abstract a GPIO controller
- * @label: for diagnostics
+ * @label: a functional name for the GPIO device, such as a part
+ *	number or the name of the SoC IP-block implementing it.
  * @gpiodev: the internal state holder, opaque struct
  * @parent: optional parent device providing the GPIOs
  * @owner: helps prevent removal of modules exporting active GPIOs

include/uapi/linux/gpio.h

@@ -16,10 +16,12 @@
 /**
  * struct gpiochip_info - Information about a certain GPIO chip
  * @name: the name of this GPIO chip
+ * @label: a functional name for this GPIO chip
  * @lines: number of GPIO lines on this chip
  */
 struct gpiochip_info {
 	char name[32];
+	char label[32];
 	__u32 lines;
 };
 

tools/gpio/lsgpio.c

@@ -54,8 +54,8 @@ int list_device(const char *device_name)
 
 		goto free_chrdev_name;
 	}
-	fprintf(stdout, "GPIO chip: %s, %u GPIO lines\n",
-		cinfo.name, cinfo.lines);
+	fprintf(stdout, "GPIO chip: %s, \"%s\", %u GPIO lines\n",
+		cinfo.name, cinfo.label, cinfo.lines);
 
 	if (close(fd) == -1)  {
 		ret = -errno;