Re: [PATCH] driver core: platform: expose numa_node to users in sysfs

For some platform devices like iommu, particually ARM smmu, users may
care about the numa locality. for example, if threads and drivers run
near iommu, they may get much better performance on dma_unmap_sg.
For other platform devices, users may still want to know the hardware
topology.

Cc: Prime Zeng <redacted>
Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Barry Song <redacted>
---
 drivers/base/platform.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index b27d0f6c18c9..7794b9a38d82 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c

@@ -1062,13 +1062,37 @@ static ssize_t driver_override_show(struct device *dev,
 }
 static DEVICE_ATTR_RW(driver_override);
 
+static ssize_t numa_node_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%d\n", dev_to_node(dev));
+}
+static DEVICE_ATTR_RO(numa_node);
+
+static umode_t platform_dev_attrs_visible(struct kobject *kobj, struct attribute *a,
+		int n)
+{
+	struct device *dev = container_of(kobj, typeof(*dev), kobj);
+
+	if (a == &dev_attr_numa_node.attr &&
+			dev_to_node(dev) == NUMA_NO_NODE)
+		return 0;
+
+	return a->mode;
+}
 
 static struct attribute *platform_dev_attrs[] = {
 	&dev_attr_modalias.attr,
+	&dev_attr_numa_node.attr,
 	&dev_attr_driver_override.attr,
 	NULL,
 };
-ATTRIBUTE_GROUPS(platform_dev);
+
+static struct attribute_group platform_dev_group = {
+	.attrs = platform_dev_attrs,
+	.is_visible = platform_dev_attrs_visible,
+};
+__ATTRIBUTE_GROUPS(platform_dev);
 
 static int platform_uevent(struct device *dev, struct kobj_uevent_env *env)
 {