[PATCH] macintosh/adb-iop: Use big-endian autopoll mask

[PATCH] macintosh/adb-iop: Use big-endian autopoll mask

[Geert Uytterhoeven]

From: Finn Thain <fthain@telegraphics.com.au>

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: c66da95a39ec ("macintosh/adb-iop: Implement SRQ autopolling")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Link: https://lore.kernel.org/r/58ba6b4eaf4d27f971f86993039da208129087af.1610778455.git.fthain@telegraphics.com.au
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Resending on behalf of Finn, as his emails seem to be dropped by vger.

To be queued in the m68k tree for v5.12.

 drivers/macintosh/adb-iop.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/macintosh/adb-iop.c b/drivers/macintosh/adb-iop.c
index 0ee3272491501c52..2633bc254935cc49 100644
--- a/drivers/macintosh/adb-iop.c
+++ b/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);
-- 
2.25.1