dax: add region 'id', 'size', and 'align' attributes

While this information is available by looking at the nvdimm parent
device that may not always be the case when/if we add support for other
memory regions. Tooling should not depend on walking a given ancestor
topology that is not guaranteed by the device's class. For example, a
device-dax instance will always have a dax_region parent, but it may not
always have a libnvdimm "dax" device as a grandparent.

Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/dax/dax.c b/drivers/dax/dax.c
index 0e499bfca41ccda4752463f770dd495259fb255e..369fccda3b1b04c33ac603a218aa4b30dc518962 100644 (file)
--- a/drivers/dax/dax.c
+++ b/drivers/dax/dax.c
@@ -75,6 +75,73 @@ struct dax_dev {
        struct resource res[0];
 };
 
+static ssize_t id_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       struct dax_region *dax_region;
+       ssize_t rc = -ENXIO;
+
+       device_lock(dev);
+       dax_region = dev_get_drvdata(dev);
+       if (dax_region)
+               rc = sprintf(buf, "%d\n", dax_region->id);
+       device_unlock(dev);
+
+       return rc;
+}
+static DEVICE_ATTR_RO(id);
+
+static ssize_t region_size_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       struct dax_region *dax_region;
+       ssize_t rc = -ENXIO;
+
+       device_lock(dev);
+       dax_region = dev_get_drvdata(dev);
+       if (dax_region)
+               rc = sprintf(buf, "%llu\n", (unsigned long long)
+                               resource_size(&dax_region->res));
+       device_unlock(dev);
+
+       return rc;
+}
+static struct device_attribute dev_attr_region_size = __ATTR(size, 0444,
+               region_size_show, NULL);
+
+static ssize_t align_show(struct device *dev,
+               struct device_attribute *attr, char *buf)
+{
+       struct dax_region *dax_region;
+       ssize_t rc = -ENXIO;
+
+       device_lock(dev);
+       dax_region = dev_get_drvdata(dev);
+       if (dax_region)
+               rc = sprintf(buf, "%u\n", dax_region->align);
+       device_unlock(dev);
+
+       return rc;
+}
+static DEVICE_ATTR_RO(align);
+
+static struct attribute *dax_region_attributes[] = {
+       &dev_attr_region_size.attr,
+       &dev_attr_align.attr,
+       &dev_attr_id.attr,
+       NULL,
+};
+
+static const struct attribute_group dax_region_attribute_group = {
+       .name = "dax_region",
+       .attrs = dax_region_attributes,
+};
+
+static const struct attribute_group *dax_region_attribute_groups[] = {
+       &dax_region_attribute_group,
+       NULL,
+};
+
 static struct inode *dax_alloc_inode(struct super_block *sb)
 {
        return kmem_cache_alloc(dax_cache, GFP_KERNEL);
@@ -200,12 +267,31 @@ void dax_region_put(struct dax_region *dax_region)
 }
 EXPORT_SYMBOL_GPL(dax_region_put);
 
+static void dax_region_unregister(void *region)
+{
+       struct dax_region *dax_region = region;
+
+       sysfs_remove_groups(&dax_region->dev->kobj,
+                       dax_region_attribute_groups);
+       dax_region_put(dax_region);
+}
+
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
                struct resource *res, unsigned int align, void *addr,
                unsigned long pfn_flags)
 {
        struct dax_region *dax_region;
 
+       /*
+        * The DAX core assumes that it can store its private data in
+        * parent->driver_data. This WARN is a reminder / safeguard for
+        * developers of device-dax drivers.
+        */
+       if (dev_get_drvdata(parent)) {
+               dev_WARN(parent, "dax core failed to setup private data\n");
+               return NULL;
+       }
+
        if (!IS_ALIGNED(res->start, align)
                        || !IS_ALIGNED(resource_size(res), align))
                return NULL;
@@ -214,6 +300,7 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
        if (!dax_region)
                return NULL;
 
+       dev_set_drvdata(parent, dax_region);
        memcpy(&dax_region->res, res, sizeof(*res));
        dax_region->pfn_flags = pfn_flags;
        kref_init(&dax_region->kref);
@@ -222,7 +309,14 @@ struct dax_region *alloc_dax_region(struct device *parent, int region_id,
        dax_region->align = align;
        dax_region->dev = parent;
        dax_region->base = addr;
+       if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
+               kfree(dax_region);
+               return NULL;;
+       }
 
+       kref_get(&dax_region->kref);
+       if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
+               return NULL;
        return dax_region;
 }
 EXPORT_SYMBOL_GPL(alloc_dax_region);