[RFC PATCH v2 6/6] driver core: add compatible string in sysfs for platform devices

[Nipun Gupta <nipun.gupta@amd.com>]

This change adds compatible string for the platform based
devices.

Signed-off-by: Nipun Gupta <nipun.gupta@amd.com>
---
 Documentation/ABI/testing/sysfs-bus-platform |  8 +++++++
 drivers/base/platform.c                      | 23 ++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-platform b/Documentation/ABI/testing/sysfs-bus-platform
index c4dfe7355c2d..d95ff83d768c 100644
--- a/Documentation/ABI/testing/sysfs-bus-platform
+++ b/Documentation/ABI/testing/sysfs-bus-platform
@@ -54,3 +54,11 @@ Description:
 		Other platform devices use, instead:
 
 			- platform:`driver name`
+
+What:		/sys/bus/platform/devices/.../compatible
+Date:		August 2022
+Contact:	Nipun Gupta <nipun.gupta@amd.com>
+Description:
+		compatible string associated with the device. This is
+		a read only and is visible if the device have "compatible"
+		property associated with it.
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 51bb2289865c..94c33efaa9b8 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1289,10 +1289,25 @@ static ssize_t driver_override_store(struct device *dev,
 }
 static DEVICE_ATTR_RW(driver_override);
 
+static ssize_t compatible_show(struct device *dev, struct device_attribute *attr,
+			      char *buf)
+{
+	const char *compat;
+	int ret;
+
+	ret = device_property_read_string(dev, "compatible", &compat);
+	if (ret != 0)
+		return 0;
+
+	return sysfs_emit(buf, "%s", compat);
+}
+static DEVICE_ATTR_RO(compatible);
+
 static struct attribute *platform_dev_attrs[] = {
 	&dev_attr_modalias.attr,
 	&dev_attr_numa_node.attr,
 	&dev_attr_driver_override.attr,
+	&dev_attr_compatible.attr,
 	NULL,
 };
 
@@ -1300,11 +1315,19 @@ static umode_t platform_dev_attrs_visible(struct kobject *kobj, struct attribute
 		int n)
 {
 	struct device *dev = container_of(kobj, typeof(*dev), kobj);
+	const char *compat;
+	int ret;
 
 	if (a == &dev_attr_numa_node.attr &&
 			dev_to_node(dev) == NUMA_NO_NODE)
 		return 0;
 
+	if (a == &dev_attr_compatible.attr) {
+		ret = device_property_read_string(dev, "compatible", &compat);
+		if (ret != 0)
+			return 0;
+	}
+
 	return a->mode;
 }
 
-- 
2.25.1