On Wed, 2015-08-19 at 23:37 +0200, Laurent Dufour wrote:

On 03/08/2015 13:00, David Laight wrote:

From: Laurent Dufour

quoted

quoted

Sent: 31 July 2015 10:30
This patch fixes several endianness issues detected when running
the HVSI
driver in little endian mode.

These issues are raised in little endian mode because the data
exchanged in
memory between the kernel and the hypervisor has to be in big
endian
format.

...

quoted

diff --git a/drivers/tty/hvc/hvsi.c b/drivers/tty/hvc/hvsi.c
index 41901997c0d6..a75146f600cb 100644
--- a/drivers/tty/hvc/hvsi.c
+++ b/drivers/tty/hvc/hvsi.c

@@ -240,9 +240,9 @@ static void hvsi_recv_control(struct

hvsi_struct *hp, uint8_t *packet,
 {
 	struct hvsi_control *header = (struct hvsi_control
*)packet;

-	switch (header->verb) {
+	switch (be16_to_cpu(header->verb)) {
 		case VSV_MODEM_CTL_UPDATE:
-			if ((header->word & HVSI_TSCD) == 0) {
+			if ((be32_to_cpu(header->word) &
HVSI_TSCD) == 0) {

It is generally best to byteswap constants.

	David

Thanks David for your review.
Regarding the byte swapping of the constants, I'm wondering if this 
 the
best way here.
For instance, Benjamin wrote a similar patch to fix another
endianness
issue (99fc1d91b8fc) and he doesn't convert the constant neither.
It think that byte swapping the constant value will impact more code,
and may not ease code reading.

Right, I disagree with byteswapping the constants at their definition
point, however maybe he meant using cpu_to_be16(CONSTANT) ?

In any case, it's pretty moot as we have the lhbrx instruction which
will do the load and byteswap and for HVSI, even if it was a tad slower
than a normal load, it would not make a noticeable difference.

Ben.