w1: optional bundling of netlink kernel replies

Applications can submit a set of commands in one packet to the kernel,
and in some cases it is required such as reading the temperature
sensor results.  This adds an option W1_CN_BUNDLE to the flags of
cn_msg to request the kernel to reply in one packet for efficiency.

The cn_msg flags now check for unknown flag values and return an error
if one is seen.  See "Proper handling of unknown flags in system
calls" http://lwn.net/Articles/588444/

This corrects the ack values returned as per the protocol standard,
namely the original ack for status messages and seq + 1 for all others
such as the data returned from a read.

Some of the common variable names have been standardized as follows.
struct cn_msg *cn
struct w1_netlink_msg *msg
struct w1_netlink_cmd *cmd
struct w1_master *dev

When an argument and a function scope variable would collide, add req_
to the argument.

Signed-off-by: David Fries <David@Fries.net>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/w1/w1_netlink.h b/drivers/w1/w1_netlink.h
index 1e9504e..c99a9ce 100644
--- a/drivers/w1/w1_netlink.h
+++ b/drivers/w1/w1_netlink.h
@@ -28,6 +28,17 @@
 #include "w1.h"
 
 /**
+ * enum w1_cn_msg_flags - bitfield flags for struct cn_msg.flags
+ *
+ * @W1_CN_BUNDLE: Request bundling replies into fewer messagse.  Be prepared
+ * to handle multiple struct cn_msg, struct w1_netlink_msg, and
+ * struct w1_netlink_cmd in one packet.
+ */
+enum w1_cn_msg_flags {
+	W1_CN_BUNDLE = 1,
+};
+
+/**
  * enum w1_netlink_message_types - message type
  *
  * @W1_SLAVE_ADD: notification that a slave device was added
@@ -49,6 +60,19 @@ enum w1_netlink_message_types {
 	W1_LIST_MASTERS,
 };
 
+/**
+ * struct w1_netlink_msg - holds w1 message type, id, and result
+ *
+ * @type: one of enum w1_netlink_message_types
+ * @status: kernel feedback for success 0 or errno failure value
+ * @len: length of data following w1_netlink_msg
+ * @id: union holding master bus id (msg.id) and slave device id (id[8]).
+ * @data: start address of any following data
+ *
+ * The base message structure for w1 messages over netlink.
+ * The netlink connector data sequence is, struct nlmsghdr, struct cn_msg,
+ * then one or more struct w1_netlink_msg (each with optional data).
+ */
 struct w1_netlink_msg
 {
 	__u8				type;
@@ -66,6 +90,7 @@ struct w1_netlink_msg
 
 /**
  * enum w1_commands - commands available for master or slave operations
+ *
  * @W1_CMD_READ: read len bytes
  * @W1_CMD_WRITE: write len bytes
  * @W1_CMD_SEARCH: initiate a standard search, returns only the slave
@@ -93,6 +118,17 @@ enum w1_commands {
 	W1_CMD_MAX
 };
 
+/**
+ * struct w1_netlink_cmd - holds the command and data
+ *
+ * @cmd: one of enum w1_commands
+ * @res: reserved
+ * @len: length of data following w1_netlink_cmd
+ * @data: start address of any following data
+ *
+ * One or more struct w1_netlink_cmd is placed starting at w1_netlink_msg.data
+ * each with optional data.
+ */
 struct w1_netlink_cmd
 {
 	__u8				cmd;