linux-kernel - Re: [PATCH 04/12] xen: make use of xenbus_read

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Date:   Thu, 3 Nov 2016 22:26:31 -0600
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, xen-devel@...ts.xen.org,
        david.vrabel@...rix.com, boris.ostrovsky@...cle.com,
        peterhuewe@....de, tpmdd@...horst.net,
        jgunthorpe@...idianresearch.com, tpmdd-devel@...ts.sourceforge.net
Subject: Re: [PATCH 04/12] xen: make use of xenbus_read_unsigned() in
 xen-tpmfront

On Mon, Oct 31, 2016 at 05:48:22PM +0100, Juergen Gross wrote:
> Use xenbus_read_unsigned() instead of xenbus_scanf() when possible.
> This requires to change the type of one read from int to unsigned,
> but this case has been wrong before: negative values are not allowed
> for the modified case.
> 
> Cc: peterhuewe@....de
> Cc: tpmdd@...horst.net
> Cc: jarkko.sakkinen@...ux.intel.com
> Cc: jgunthorpe@...idianresearch.com
> Cc: tpmdd-devel@...ts.sourceforge.net
> 
> Signed-off-by: Juergen Gross <jgross@...e.com>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

/Jarkko

> ---
>  drivers/char/tpm/xen-tpmfront.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
> index 62028f4..50072cc 100644
> --- a/drivers/char/tpm/xen-tpmfront.c
> +++ b/drivers/char/tpm/xen-tpmfront.c
> @@ -337,18 +337,14 @@ static int tpmfront_resume(struct xenbus_device *dev)
>  static void backend_changed(struct xenbus_device *dev,
>  		enum xenbus_state backend_state)
>  {
> -	int val;
> -
>  	switch (backend_state) {
>  	case XenbusStateInitialised:
>  	case XenbusStateConnected:
>  		if (dev->state == XenbusStateConnected)
>  			break;
>  
> -		if (xenbus_scanf(XBT_NIL, dev->otherend,
> -				"feature-protocol-v2", "%d", &val) < 0)
> -			val = 0;
> -		if (!val) {
> +		if (!xenbus_read_unsigned(dev->otherend, "feature-protocol-v2",
> +					  0)) {
>  			xenbus_dev_fatal(dev, -EINVAL,
>  					"vTPM protocol 2 required");
>  			return;
> -- 
> 2.6.6
>