macintosh/adb-iop: Use big-endian autopoll mask

As usual, the available documentation is inadequate and leaves endianness
unspecified for message data. However, testing shows that this patch does
improve correctness. The mistake should have been detected earlier but it
was obscured by other bugs. In testing, this patch reinstated pre-v5.9
behaviour. The old driver bugs remain and ADB input devices may stop
working. But that appears to be unrelated.

Cc: Joshua Thompson <funaho@jurai.org>
Fixes: c66da95a ("macintosh/adb-iop: Implement SRQ autopolling")
Tested-by: NStan Johnson <userm57@yahoo.com>
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/20210125074524.3027452-1-geert@linux-m68k.org

drivers/macintosh/adb-iop.c

@@ -19,6 +19,7 @@
 #include <asm/macints.h>
 #include <asm/mac_iop.h>
 #include <asm/adb_iop.h>
+#include <asm/unaligned.h>
 
 #include <linux/adb.h>
 
@@ -249,7 +250,7 @@ static void adb_iop_set_ap_complete(struct iop_msg *msg)
 {
 	struct adb_iopmsg *amsg = (struct adb_iopmsg *)msg->message;
 
-	autopoll_devs = (amsg->data[1] << 8) | amsg->data[0];
+	autopoll_devs = get_unaligned_be16(amsg->data);
 	if (autopoll_devs & (1 << autopoll_addr))
 		return;
 	autopoll_addr = autopoll_devs ? (ffs(autopoll_devs) - 1) : 0;
@@ -266,8 +267,7 @@ static int adb_iop_autopoll(int devs)
 	amsg.flags = ADB_IOP_SET_AUTOPOLL | (mask ? ADB_IOP_AUTOPOLL : 0);
 	amsg.count = 2;
 	amsg.cmd = 0;
-	amsg.data[0] = mask & 0xFF;
-	amsg.data[1] = (mask >> 8) & 0xFF;
+	put_unaligned_be16(mask, amsg.data);
 
 	iop_send_message(ADB_IOP, ADB_CHAN, NULL, sizeof(amsg), (__u8 *)&amsg,
 			 adb_iop_set_ap_complete);