linux-kernel - Re: [PATCH] staging: fusb302: don't bitshift _

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Date:   Fri, 16 Jun 2017 11:11:50 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Frans Klaver <fransklaver@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Yueyao Zhu <yueyao.zhu@...il.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Guru Das Srinagesh <gurooodas@...il.com>,
        Javier Martinez Canillas <javier@...hile0.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: fusb302: don't bitshift __le16 type

On Fri, Jun 16, 2017 at 07:45:56PM +0200, Frans Klaver wrote:
> The header field in struct pd_message is declared as an __le16 type. The
> data in the message is supposed to be little endian. This means we don't
> have to go and shift the individual bytes into position when we're
> filling the buffer, we can just copy the contents right away. As an
> added benefit we don't get fishy results on big endian systems anymore.
> 
> Signed-off-by: Frans Klaver <fransklaver@...il.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>  drivers/staging/typec/fusb302/fusb302.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/typec/fusb302/fusb302.c b/drivers/staging/typec/fusb302/fusb302.c
> index 4a356e509fe4..03a3809d18f0 100644
> --- a/drivers/staging/typec/fusb302/fusb302.c
> +++ b/drivers/staging/typec/fusb302/fusb302.c
> @@ -1039,8 +1039,8 @@ static int fusb302_pd_send_message(struct fusb302_chip *chip,
>  	}
>  	/* packsym tells the FUSB302 chip that the next X bytes are payload */
>  	buf[pos++] = FUSB302_TKN_PACKSYM | (len & 0x1F);
> -	buf[pos++] = msg->header & 0xFF;
> -	buf[pos++] = (msg->header >> 8) & 0xFF;
> +	memcpy(&buf[pos], &msg->header, sizeof(msg->header));
> +	pos += sizeof(msg->header);
>  
>  	len -= 2;
>  	memcpy(&buf[pos], msg->payload, len);
> -- 
> 2.13.0
>