libertas: change inference about buffer size in lbs_cmd()

sizeof(*cmd) is going to give the total size of the data structure that
we allocated, more often than not. But the size of the command to be
_sent_ could be a lot smaller, as it is in the KEY_MATERIAL and
SUBSCRIBE_EVENT commands for example. So swap them round; let the caller
set the _command_ size explicitly in the header, and infer the
maximum response size from the data structure.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/net/wireless/libertas/cmd.h b/drivers/net/wireless/libertas/cmd.h
index 6efb81ec597e..b9ab85cc7913 100644
--- a/drivers/net/wireless/libertas/cmd.h
+++ b/drivers/net/wireless/libertas/cmd.h
@@ -6,13 +6,15 @@
 #include "hostcmd.h"
 #include "dev.h"
 
-#define lbs_cmd(priv, cmdnr, cmd, cb, cb_arg)   \
-        __lbs_cmd(priv, cmdnr, &(cmd)->hdr, sizeof(*(cmd)), cb, cb_arg)
+/* lbs_cmd() infers the size of the buffer to copy data back into, from
+   the size of the target of the pointer. Since the command to be sent 
+   may often be smaller, that size is set in cmd->size by the caller.*/
+#define lbs_cmd(priv, cmdnr, cmd, cb, cb_arg)   ({              \
+        uint16_t __sz = le16_to_cpu((cmd)->hdr.size);           \
+        (cmd)->hdr.size = cpu_to_le16(sizeof(*(cmd)));          \
+        __lbs_cmd(priv, cmdnr, &(cmd)->hdr, __sz, cb, cb_arg);  \
+})
 
-
-/* lbs_cmd_with_response() infers the size of the command to be _sent_
-   and requires that the caller sets cmd->size to the (LE) size of
-   the _response_ buffer. */
 #define lbs_cmd_with_response(priv, cmdnr, cmd) \
         lbs_cmd(priv, cmdnr, cmd, lbs_cmd_copyback, (unsigned long) (cmd))