Re: [Xen-devel] [PATCH v3] xen-netback: prefer xenbus_scanf() over xenbus_gather()

[David Miller]

From: "Jan Beulich" 
Date: Tue, 08 Nov 2016 00:45:53 -0700

> For single items being collected this should be preferred as being more
> typesafe (as the compiler can check format string and to-be-written-to
> variable match) and more efficient (requiring one less parameter to be
> passed).
> 
> Signed-off-by: Jan Beulich 
> ---
> v3: For consistency with other code don't consider zero an error
> (utilizing that xenbus_scanf() at present won't return zero).
> v2: Avoid commit message to continue from subject.

Applied to net-next, thanks.

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Re: [Xen-devel] [PATCH v3] xen-netback: prefer xenbus_scanf() over xenbus_gather()

[Paul Durrant]

> -Original Message-
> From: Jan Beulich [mailto:jbeul...@suse.com]
> Sent: 08 November 2016 07:46
> To: Paul Durrant ; Wei Liu 
> Cc: xen-devel ; net...@vger.kernel.org
> Subject: [PATCH v3] xen-netback: prefer xenbus_scanf() over
> xenbus_gather()
> 
> For single items being collected this should be preferred as being more
> typesafe (as the compiler can check format string and to-be-written-to
> variable match) and more efficient (requiring one less parameter to be
> passed).
> 
> Signed-off-by: Jan Beulich 

LGTM

Reviewed-by: Paul Durrant 

> ---
> v3: For consistency with other code don't consider zero an error
> (utilizing that xenbus_scanf() at present won't return zero).
> v2: Avoid commit message to continue from subject.
> ---
>  drivers/net/xen-netback/xenbus.c |   12 ++--
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> --- 4.9-rc4/drivers/net/xen-netback/xenbus.c
> +++ 4.9-rc4-xen-netback-prefer-xenbus_scanf/drivers/net/xen-
> netback/xenbus.c
> @@ -889,16 +889,16 @@ static int connect_ctrl_ring(struct back
>   unsigned int evtchn;
>   int err;
> 
> - err = xenbus_gather(XBT_NIL, dev->otherend,
> - "ctrl-ring-ref", "%u", , NULL);
> - if (err)
> + err = xenbus_scanf(XBT_NIL, dev->otherend,
> +"ctrl-ring-ref", "%u", );
> + if (err < 0)
>   goto done; /* The frontend does not have a control ring */
> 
>   ring_ref = val;
> 
> - err = xenbus_gather(XBT_NIL, dev->otherend,
> - "event-channel-ctrl", "%u", , NULL);
> - if (err) {
> + err = xenbus_scanf(XBT_NIL, dev->otherend,
> +"event-channel-ctrl", "%u", );
> + if (err < 0) {
>   xenbus_dev_fatal(dev, err,
>"reading %s/event-channel-ctrl",
>dev->otherend);
> 
> 


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[Xen-devel] [PATCH v3] xen-netback: prefer xenbus_scanf() over xenbus_gather()

[Jan Beulich]

For single items being collected this should be preferred as being more
typesafe (as the compiler can check format string and to-be-written-to
variable match) and more efficient (requiring one less parameter to be
passed).

Signed-off-by: Jan Beulich 
---
v3: For consistency with other code don't consider zero an error
(utilizing that xenbus_scanf() at present won't return zero).
v2: Avoid commit message to continue from subject.
---
 drivers/net/xen-netback/xenbus.c |   12 ++--
 1 file changed, 6 insertions(+), 6 deletions(-)

--- 4.9-rc4/drivers/net/xen-netback/xenbus.c
+++ 4.9-rc4-xen-netback-prefer-xenbus_scanf/drivers/net/xen-netback/xenbus.c
@@ -889,16 +889,16 @@ static int connect_ctrl_ring(struct back
unsigned int evtchn;
int err;
 
-   err = xenbus_gather(XBT_NIL, dev->otherend,
-   "ctrl-ring-ref", "%u", , NULL);
-   if (err)
+   err = xenbus_scanf(XBT_NIL, dev->otherend,
+  "ctrl-ring-ref", "%u", );
+   if (err < 0)
goto done; /* The frontend does not have a control ring */
 
ring_ref = val;
 
-   err = xenbus_gather(XBT_NIL, dev->otherend,
-   "event-channel-ctrl", "%u", , NULL);
-   if (err) {
+   err = xenbus_scanf(XBT_NIL, dev->otherend,
+  "event-channel-ctrl", "%u", );
+   if (err < 0) {
xenbus_dev_fatal(dev, err,
 "reading %s/event-channel-ctrl",
 dev->otherend);




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