[PATCH] dpaa_eth: Fix comparing pointer to 0

[PATCH] dpaa_eth: Fix comparing pointer to 0

[Aishwarya Ramakrishnan]

Fixes coccicheck warning:
./drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2110:30-31:
WARNING comparing pointer to 0

Avoid pointer type value compared to 0.

Signed-off-by: Aishwarya Ramakrishnan <aishwaryarj100@gmail.com>
---
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index 2cd1f8efdfa3..c4416a5f8816 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -2107,7 +2107,7 @@ static int dpaa_a050385_wa(struct net_device *net_dev, struct sk_buff **s)
 
 	/* Workaround for DPAA_A050385 requires data start to be aligned */
 	start = PTR_ALIGN(new_skb->data, DPAA_A050385_ALIGN);
-	if (start - new_skb->data != 0)
+	if (start - new_skb->data)
 		skb_reserve(new_skb, start - new_skb->data);
 
 	skb_put(new_skb, skb->len);
-- 
2.17.1

Re: [PATCH] dpaa_eth: Fix comparing pointer to 0

[David Miller]

From: Aishwarya Ramakrishnan <aishwaryarj100@gmail.com>
Date: Mon, 27 Apr 2020 16:02:30 +0530

> Fixes coccicheck warning:
> ./drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2110:30-31:
> WARNING comparing pointer to 0
> 
> Avoid pointer type value compared to 0.
> 
> Signed-off-by: Aishwarya Ramakrishnan <aishwaryarj100@gmail.com>

Applied, thanks.

Re: [PATCH] dpaa_eth: Fix comparing pointer to 0

[Markus Elfring]

> Fixes coccicheck warning:
> ./drivers/net/ethernet/freescale/dpaa/dpaa_eth.c:2110:30-31:
> WARNING comparing pointer to 0

Such information is actually provided by a known script for
the semantic patch language.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/scripts/coccinelle/null/badzero.cocci


> Avoid pointer type value compared to 0.

But I suggest to reconsider corresponding software development consequences
also around mentioned implementation details.


…
> +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> @@ -2107,7 +2107,7 @@ static int dpaa_a050385_wa(struct net_device *net_dev, struct sk_buff **s)
…
>  	start = PTR_ALIGN(new_skb->data, DPAA_A050385_ALIGN);
> -	if (start - new_skb->data != 0)
> +	if (start - new_skb->data)
>  		skb_reserve(new_skb, start - new_skb->data);
…


I interpret the source code in the way that a subtraction is performed
with two pointers. I would expect that such a pointer difference
has got an integral data type.
Will this view trigger any further software evolution?

Regards,
Markus