switchdev: introduce transaction item queue for attr_set and obj_add

Now, the memory allocation in prepare/commit state is done separatelly
in each driver (rocker). Introduce the similar mechanism in generic
switchdev code, in form of queue. That can be used not only for memory
allocations, but also for different items. Abort item destruction
is handled as well.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 19 insertions, 0 deletions

diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt
index 67e43ee7840a..9f9e2587b347 100644
--- a/Documentation/networking/switchdev.txt
+++ b/Documentation/networking/switchdev.txt
@@ -369,3 +369,22 @@ The driver can monitor for updates to arp_tbl using the netevent notifier
 NETEVENT_NEIGH_UPDATE.  The device can be programmed with resolved nexthops
 for the routes as arp_tbl updates.  The driver implements ndo_neigh_destroy
 to know when arp_tbl neighbor entries are purged from the port.
+
+Transaction item queue
+^^^^^^^^^^^^^^^^^^^^^^
+
+For switchdev ops attr_set and obj_add, there is a 2 phase transaction model
+used. First phase is to "prepare" anything needed, including various checks,
+memory allocation, etc. The goal is to handle the stuff that is not unlikely
+to fail here. The second phase is to "commit" the actual changes.
+
+Switchdev provides an inftrastructure for sharing items (for example memory
+allocations) between the two phases.
+
+The object created by a driver in "prepare" phase and it is queued up by:
+switchdev_trans_item_enqueue()
+During the "commit" phase, the driver gets the object by:
+switchdev_trans_item_dequeue()
+
+If a transaction is aborted during "prepare" phase, switchdev code will handle
+cleanup of the queued-up objects.