[PATCH v2 03/10] gpio: aggregator: add read-only 'dev_name' configfs attribute

[Koichiro Den <koichiro.den@xxxxxxxxxxxxx>]

Add a read-only 'dev_name' attribute to configfs interface, which
exposes the platform bus device name. Users can easily identify which
gpiochip<N> has been created as follows:

$ cat /sys/kernel/config/gpio-aggregator/<aggregator-name>/dev_name
  gpio-aggregator.0
$ ls -d /sys/devices/platform/gpio-aggregator.0/gpiochip*
  gpiochip3

Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
---
 drivers/gpio/gpio-aggregator.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
index c63cf3067ce7..76d3a8677308 100644
--- a/drivers/gpio/gpio-aggregator.c
+++ b/drivers/gpio/gpio-aggregator.c
@@ -732,6 +732,23 @@ static struct configfs_attribute *gpio_aggr_line_attrs[] = {
 	NULL
 };
 
+static ssize_t
+gpio_aggr_device_dev_name_show(struct config_item *item, char *page)
+{
+	struct gpio_aggregator *aggr = to_gpio_aggregator(item);
+	struct platform_device *pdev;
+
+	guard(mutex)(&aggr->lock);
+
+	pdev = aggr->pdev;
+	if (pdev)
+		return sprintf(page, "%s\n", dev_name(&pdev->dev));
+
+	return sprintf(page, "%s.%d\n", DRV_NAME, aggr->id);
+}
+
+CONFIGFS_ATTR_RO(gpio_aggr_device_, dev_name);
+
 static ssize_t
 gpio_aggr_device_live_show(struct config_item *item, char *page)
 {
@@ -781,6 +798,7 @@ gpio_aggr_device_live_store(struct config_item *item, const char *page,
 CONFIGFS_ATTR(gpio_aggr_device_, live);
 
 static struct configfs_attribute *gpio_aggr_device_attrs[] = {
+	&gpio_aggr_device_attr_dev_name,
 	&gpio_aggr_device_attr_live,
 	NULL
 };
-- 
2.45.2