2021-11-18 09:48:17

by Yang Li

[permalink] [raw]
Subject: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

do_div() does a 64-by-32 division. Here the divisor is an
unsigned long which on some platforms is 64 bit wide. So use
div64_ul instead of do_div to avoid a possible truncation.

Eliminate the following coccicheck warning:
./drivers/net/ethernet/renesas/ravb_main.c:2492:1-7: WARNING:
do_div() does a 64-by-32 division, please consider using div64_ul
instead.

Reported-by: Abaci Robot <[email protected]>
Signed-off-by: Yang Li <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Sergey Shtylyov <[email protected]>
---

change in v2:
--According to Geert's suggestion
replace #include <asm/div64.h> by
#include <linux/math64.h>
--According to Sergey's suggestion
Merge two statements into one

drivers/net/ethernet/renesas/ravb_main.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index b4c597f..151cce2 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -30,8 +30,7 @@
#include <linux/spinlock.h>
#include <linux/sys_soc.h>
#include <linux/reset.h>
-
-#include <asm/div64.h>
+#include <linux/math64.h>

#include "ravb.h"

@@ -2488,8 +2487,7 @@ static int ravb_set_gti(struct net_device *ndev)
if (!rate)
return -EINVAL;

- inc = 1000000000ULL << 20;
- do_div(inc, rate);
+ inc = div64_ul(1000000000ULL << 20, rate);

if (inc < GTI_TIV_MIN || inc > GTI_TIV_MAX) {
dev_err(dev, "gti.tiv increment 0x%llx is outside the range 0x%x - 0x%x\n",
--
1.8.3.1



2021-11-18 10:08:01

by Sergey Shtylyov

[permalink] [raw]
Subject: Re: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

On 18.11.2021 12:48, Yang Li wrote:

> do_div() does a 64-by-32 division. Here the divisor is an
> unsigned long which on some platforms is 64 bit wide. So use
> div64_ul instead of do_div to avoid a possible truncation.
>
> Eliminate the following coccicheck warning:
> ./drivers/net/ethernet/renesas/ravb_main.c:2492:1-7: WARNING:
> do_div() does a 64-by-32 division, please consider using div64_ul
> instead.
>
> Reported-by: Abaci Robot <[email protected]>
> Signed-off-by: Yang Li <[email protected]>
> Reviewed-by: Geert Uytterhoeven <[email protected]>
> Reviewed-by: Sergey Shtylyov <[email protected]>

I haven't given you this tag, yet I was going to give you one, so
it's OK finally. :-)

[...]

MBR, Sergey

2021-11-20 04:30:24

by patchwork-bot+netdevbpf

[permalink] [raw]
Subject: Re: [PATCH -next v2] ethernet: renesas: Use div64_ul instead of do_div

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <[email protected]>:

On Thu, 18 Nov 2021 17:48:03 +0800 you wrote:
> do_div() does a 64-by-32 division. Here the divisor is an
> unsigned long which on some platforms is 64 bit wide. So use
> div64_ul instead of do_div to avoid a possible truncation.
>
> Eliminate the following coccicheck warning:
> ./drivers/net/ethernet/renesas/ravb_main.c:2492:1-7: WARNING:
> do_div() does a 64-by-32 division, please consider using div64_ul
> instead.
>
> [...]

Here is the summary with links:
- [-next,v2] ethernet: renesas: Use div64_ul instead of do_div
https://git.kernel.org/netdev/net-next/c/d9f31aeaa1e5

You are awesome, thank you!
--
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https://korg.docs.kernel.org/patchwork/pwbot.html