Documentation update for the driver model core
This patch (as1509) documents two important points regarding the use
of device structures in the driver model:
Structures must be initialized to all 0's before they are
passed to device_initialize().
Structures must not be passed to device_add() or
device_register() more than once.
Although these restrictions have applied ever since the driver model
was first created, they have not been mentioned anywhere.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4a67cc0..ad29e92 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -632,6 +632,11 @@
* may be used for reference counting of @dev after calling this
* function.
*
+ * All fields in @dev must be initialized by the caller to 0, except
+ * for those explicitly set to some other value. The simplest
+ * approach is to use kzalloc() to allocate the structure containing
+ * @dev.
+ *
* NOTE: Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.
*/
@@ -930,6 +935,13 @@
* to the global and sibling lists for the device, then
* adds it to the other relevant subsystems of the driver model.
*
+ * Do not call this routine or device_register() more than once for
+ * any device structure. The driver model core is not designed to work
+ * with devices that get unregistered and then spring back to life.
+ * (Among other things, it's very hard to guarantee that all references
+ * to the previous incarnation of @dev have been dropped.) Allocate
+ * and register a fresh new struct device instead.
+ *
* NOTE: _Never_ directly free @dev after calling this function, even
* if it returned an error! Always use put_device() to give up your
* reference instead.
@@ -1090,6 +1102,9 @@
* have a clearly defined need to use and refcount the device
* before it is added to the hierarchy.
*
+ * For more information, see the kerneldoc for device_initialize()
+ * and device_add().
+ *
* NOTE: _Never_ directly free @dev after calling this function, even
* if it returned an error! Always use put_device() to give up the
* reference initialized in this function instead.
