Re: [Xen-devel] [PATCH v2] xen/manage: correct return value check on xenbus_scanf()

[Juergen Gross <jgross@xxxxxxxx>]

On 08/11/16 08:44, Jan Beulich wrote:
> A negative return value indicates an error; in fact the function at
> present won't ever return zero.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Juergen Gross <jgross@xxxxxxxx>

> ---
> v2: For consistency with other code don't consider zero an error
>     (utilizing that xenbus_scanf() at present won't return zero).
>     Adjust commit message accordingly.
> ---
>  drivers/xen/manage.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- 4.9-rc4/drivers/xen/manage.c
> +++ 4.9-rc4-xen-manage-xenbus_scanf/drivers/xen/manage.c
> @@ -277,7 +277,7 @@ static void sysrq_handler(struct xenbus_
>       err = xenbus_transaction_start(&xbt);
>       if (err)
>               return;
> -     if (!xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key)) {
> +     if (xenbus_scanf(xbt, "control", "sysrq", "%c", &sysrq_key) < 0) {
>               pr_err("Unable to read sysrq code in control/sysrq\n");
>               xenbus_transaction_end(xbt, 1);
>               return;
> 
> 


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