linux-kernel - RE: [PATCH] powerpc/hvsi: Fix endianness issues in the HVSI driver

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Date:	Mon, 3 Aug 2015 11:00:18 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Laurent Dufour' <ldufour@...ux.vnet.ibm.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] powerpc/hvsi: Fix endianness issues in the HVSI driver

From: Laurent Dufour
> 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.
...
> 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