[U-Boot] [PATCH 2/4] net: tweak eth_device layout to simplify enetaddr use

[Mike Frysinger]

The current eth_device leaves a 2 byte hole after "enetaddr" and before
"iobase".  Since the enetaddr member has to be 6 bytes, we might as well
fill that 2 byte hole with something useful.

Further, most device drivers want to load enetaddr from memory into the
hardware as 1 32bit value and 1 16bit value.

So re-arrange the structure slightly, and add an anonymous union to make
eth_device even better:
 - expand the name field to fill the 2 byte hole
 - make sure enetaddr is aligned, and provides 32bit/16bit members

Now device driver code can simply use "dev->enetaddr32" and
"dev->enetaddr16[2]" to access the values without having to manually
shift the bytes out of dev->enetaddr.

Signed-off-by: Mike Frysinger <vapier at gentoo.org>
---
 include/net.h |   13 +++++++++++--
 1 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/include/net.h b/include/net.h
index b4acd8f..e8c12d9 100644
--- a/include/net.h
+++ b/include/net.h
@@ -73,8 +73,17 @@ enum eth_state_t {
 };
 
 struct eth_device {
-	char name[16];
-	unsigned char enetaddr[6];
+	/* Keep enetaddr at start so it is guaranteed aligned */
+	union {
+		u32 enetaddr32;
+		u16 enetaddr16[3];
+		unsigned char enetaddr[6];
+	};
+	/*
+	 * Note: name size is picked to fill the holes in memory after
+	 * enetaddr, and to match up to alignment for following "int".
+	 */
+	char name[18];
 	int iobase;
 	int state;
 
-- 
1.7.6.1