drivers: base: add coredump driver ops

This adds the coredump driver operation. When the driver defines it
a coredump file is added in the sysfs folder of the device upon
driver binding. The file is removed when the driver is unbound.
User-space can trigger a coredump for this device by echo'ing to
the coredump file.
Signed-off-by: Arend van Spriel <aspriel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/dd.c

@@ -288,6 +288,18 @@ static void driver_bound(struct device *dev)
 	kobject_uevent(&dev->kobj, KOBJ_BIND);
 }
 
+static ssize_t coredump_store(struct device *dev, struct device_attribute *attr,
+			    const char *buf, size_t count)
+{
+	device_lock(dev);
+	if (dev->driver->coredump)
+		dev->driver->coredump(dev);
+	device_unlock(dev);
+
+	return count;
+}
+static DEVICE_ATTR_WO(coredump);
+
 static int driver_sysfs_add(struct device *dev)
 {
 	int ret;
@@ -297,14 +309,26 @@ static int driver_sysfs_add(struct device *dev)
 					     BUS_NOTIFY_BIND_DRIVER, dev);
 
 	ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj,
+				kobject_name(&dev->kobj));
+	if (ret)
+		goto fail;
+
+	ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
+				"driver");
+	if (ret)
+		goto rm_dev;
+
+	if (!IS_ENABLED(CONFIG_DEV_COREDUMP) || !dev->driver->coredump ||
+	    !device_create_file(dev, &dev_attr_coredump))
+		return 0;
+
+	sysfs_remove_link(&dev->kobj, "driver");
+
+rm_dev:
+	sysfs_remove_link(&dev->driver->p->kobj,
 			  kobject_name(&dev->kobj));
-	if (ret == 0) {
-		ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj,
-					"driver");
-		if (ret)
-			sysfs_remove_link(&dev->driver->p->kobj,
-					kobject_name(&dev->kobj));
-	}
+
+fail:
 	return ret;
 }
 
@@ -313,6 +337,8 @@ static void driver_sysfs_remove(struct device *dev)
 	struct device_driver *drv = dev->driver;
 
 	if (drv) {
+		if (drv->coredump)
+			device_remove_file(dev, &dev_attr_coredump);
 		sysfs_remove_link(&drv->p->kobj, kobject_name(&dev->kobj));
 		sysfs_remove_link(&dev->kobj, "driver");
 	}

include/linux/device.h

@@ -287,6 +287,7 @@ struct device_driver {
 	const struct attribute_group **groups;
 
 	const struct dev_pm_ops *pm;
+	int (*coredump) (struct device *dev);
 
 	struct driver_private *p;
 };
@@ -300,7 +301,6 @@ extern struct device_driver *driver_find(const char *name,
 extern int driver_probe_done(void);
 extern void wait_for_device_probe(void);
 
-
 /* sysfs interface for exporting driver attributes */
 
 struct driver_attribute {