[PATCH] USB: gadget: udc: s3c2410_udc: Remove pointless NULL check in s3c2410_udc_nuke

[PATCH] USB: gadget: udc: s3c2410_udc: Remove pointless NULL check in s3c2410_udc_nuke

[Nathan Chancellor]

Clang warns:

drivers/usb/gadget/udc/s3c2410_udc.c:255:11: warning: comparison of
address of 'ep->queue' equal to a null pointer is always false
[-Wtautological-pointer-compare]
        if (&ep->queue == NULL)
             ~~~~^~~~~    ~~~~
1 warning generated.

It is not wrong, queue is not a pointer so if ep is not NULL, the
address of queue cannot be NULL. No other driver does a check like this
and this check has been around since the driver was first introduced,
presumably with no issues so it does not seem like this check should be
something else. Just remove it.

Commit afe956c577b2d ("kbuild: Enable -Wtautological-compare") exposed
this but it is not the root cause of the warning.

Fixes: 3fc154b6b8134 ("USB Gadget driver for Samsung s3c2410 ARM SoC")
Link: https://github.com/ClangBuiltLinux/linux/issues/1004
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 drivers/usb/gadget/udc/s3c2410_udc.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/usb/gadget/udc/s3c2410_udc.c b/drivers/usb/gadget/udc/s3c2410_udc.c
index 0507a2ca0f552..80002d97b59d8 100644
--- a/drivers/usb/gadget/udc/s3c2410_udc.c
+++ b/drivers/usb/gadget/udc/s3c2410_udc.c
@@ -251,10 +251,6 @@ static void s3c2410_udc_done(struct s3c2410_ep *ep,
 static void s3c2410_udc_nuke(struct s3c2410_udc *udc,
 		struct s3c2410_ep *ep, int status)
 {
-	/* Sanity check */
-	if (&ep->queue == NULL)
-		return;
-
 	while (!list_empty(&ep->queue)) {
 		struct s3c2410_request *req;
 		req = list_entry(ep->queue.next, struct s3c2410_request,

base-commit: ae83d0b416db002fe95601e7f97f64b59514d936
-- 
2.26.2

Re: [PATCH] USB: gadget: udc: s3c2410_udc: Remove pointless NULL check in s3c2410_udc_nuke

[Nick Desaulniers]

On Thu, Apr 23, 2020 at 9:30 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Clang warns:
>
> drivers/usb/gadget/udc/s3c2410_udc.c:255:11: warning: comparison of
> address of 'ep->queue' equal to a null pointer is always false
> [-Wtautological-pointer-compare]
>         if (&ep->queue == NULL)
>              ~~~~^~~~~    ~~~~
> 1 warning generated.
>
> It is not wrong, queue is not a pointer so if ep is not NULL, the
> address of queue cannot be NULL. No other driver does a check like this
> and this check has been around since the driver was first introduced,
> presumably with no issues so it does not seem like this check should be
> something else. Just remove it.
>
> Commit afe956c577b2d ("kbuild: Enable -Wtautological-compare") exposed
> this but it is not the root cause of the warning.
>
> Fixes: 3fc154b6b8134 ("USB Gadget driver for Samsung s3c2410 ARM SoC")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1004
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Thanks for the patch!  If anything, I'd be happy to see some more NULL
checks against `ep`, though the callers of s3c2410_udc_nuke() also
seem quite confident that the pointer is not NULL.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  drivers/usb/gadget/udc/s3c2410_udc.c | 4 ----
>  1 file changed, 4 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/s3c2410_udc.c b/drivers/usb/gadget/udc/s3c2410_udc.c
> index 0507a2ca0f552..80002d97b59d8 100644
> --- a/drivers/usb/gadget/udc/s3c2410_udc.c
> +++ b/drivers/usb/gadget/udc/s3c2410_udc.c
> @@ -251,10 +251,6 @@ static void s3c2410_udc_done(struct s3c2410_ep *ep,
>  static void s3c2410_udc_nuke(struct s3c2410_udc *udc,
>                 struct s3c2410_ep *ep, int status)
>  {
> -       /* Sanity check */
> -       if (&ep->queue == NULL)
> -               return;
> -
>         while (!list_empty(&ep->queue)) {
>                 struct s3c2410_request *req;
>                 req = list_entry(ep->queue.next, struct s3c2410_request,
>
> base-commit: ae83d0b416db002fe95601e7f97f64b59514d936
> --
> 2.26.2
>
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-- 
Thanks,
~Nick Desaulniers