* [PATCH] net: dsa: ocelot: use div64_u64() instead of do_div()
@ 2022-02-09 8:39 Qing Wang
2022-02-09 11:14 ` Vladimir Oltean
0 siblings, 1 reply; 2+ messages in thread
From: Qing Wang @ 2022-02-09 8:39 UTC (permalink / raw)
To: Vladimir Oltean, Claudiu Manoil, Alexandre Belloni,
UNGLinuxDriver, Andrew Lunn, Vivien Didelot, Florian Fainelli,
David S. Miller, Jakub Kicinski, netdev, linux-kernel
Cc: Wang Qing
From: Wang Qing <wangqing@vivo.com>
do_div() does a 64-by-32 division.
When the divisor is u64, do_div() truncates it to 32 bits, this means it
can test non-zero and be truncated to zero for division.
fix do_div.cocci warning:
do_div() does a 64-by-32 division, please consider using div64_u64 instead.
Signed-off-by: Wang Qing <wangqing@vivo.com>
---
drivers/net/dsa/ocelot/felix_vsc9959.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
index bf8d382..5c2482f
--- a/drivers/net/dsa/ocelot/felix_vsc9959.c
+++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
@@ -1178,7 +1178,7 @@ static void vsc9959_new_base_time(struct ocelot *ocelot, ktime_t base_time,
if (base_time < current_time) {
u64 nr_of_cycles = current_time - base_time;
- do_div(nr_of_cycles, cycle_time);
+ div64_u64(nr_of_cycles, cycle_time);
new_base_time += cycle_time * (nr_of_cycles + 1);
}
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] net: dsa: ocelot: use div64_u64() instead of do_div()
2022-02-09 8:39 [PATCH] net: dsa: ocelot: use div64_u64() instead of do_div() Qing Wang
@ 2022-02-09 11:14 ` Vladimir Oltean
0 siblings, 0 replies; 2+ messages in thread
From: Vladimir Oltean @ 2022-02-09 11:14 UTC (permalink / raw)
To: Qing Wang
Cc: Claudiu Manoil, Alexandre Belloni, UNGLinuxDriver, Andrew Lunn,
Vivien Didelot, Florian Fainelli, David S. Miller,
Jakub Kicinski, netdev, linux-kernel
Hi Wang,
On Wed, Feb 09, 2022 at 12:39:02AM -0800, Qing Wang wrote:
> From: Wang Qing <wangqing@vivo.com>
>
> do_div() does a 64-by-32 division.
> When the divisor is u64, do_div() truncates it to 32 bits, this means it
> can test non-zero and be truncated to zero for division.
>
> fix do_div.cocci warning:
> do_div() does a 64-by-32 division, please consider using div64_u64 instead.
>
> Signed-off-by: Wang Qing <wangqing@vivo.com>
> ---
> drivers/net/dsa/ocelot/felix_vsc9959.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/dsa/ocelot/felix_vsc9959.c b/drivers/net/dsa/ocelot/felix_vsc9959.c
> index bf8d382..5c2482f
> --- a/drivers/net/dsa/ocelot/felix_vsc9959.c
> +++ b/drivers/net/dsa/ocelot/felix_vsc9959.c
> @@ -1178,7 +1178,7 @@ static void vsc9959_new_base_time(struct ocelot *ocelot, ktime_t base_time,
> if (base_time < current_time) {
> u64 nr_of_cycles = current_time - base_time;
>
> - do_div(nr_of_cycles, cycle_time);
> + div64_u64(nr_of_cycles, cycle_time);
> new_base_time += cycle_time * (nr_of_cycles + 1);
> }
>
> --
> 2.7.4
>
I would prefer that you teach your scripts that, if a range check exists
for the divisor prior to the division, it gets taken into consideration.
vsc9959_qos_port_tas_set:
if (taprio->cycle_time > NSEC_PER_SEC ||
taprio->cycle_time_extension >= NSEC_PER_SEC)
return -EINVAL;
vsc9959_new_base_time(ocelot, taprio->base_time,
taprio->cycle_time, &base_ts);
vsc9959_psfp_sgi_set:
if (sgi->cycletime < VSC9959_PSFP_GATE_CYCLETIME_MIN ||
sgi->cycletime > NSEC_PER_SEC)
return -EINVAL;
vsc9959_new_base_time(ocelot, sgi->basetime, sgi->cycletime, &base_ts);
So all callers provide a cycle_time argument that is smaller than
NSEC_PER_SEC (1000000000L = 0x3B9ACA00 => fits on 32 bits).
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-02-09 12:08 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-02-09 8:39 [PATCH] net: dsa: ocelot: use div64_u64() instead of do_div() Qing Wang
2022-02-09 11:14 ` Vladimir Oltean
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).