Re: [PATCH] net: wireless: ath: use div64_u64() instead of do_div()

Qing Wang [off-list ref] writes:

As you have been pointed out in your other patches, do_div() and
div64_u64() work differently.

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From: Kalle Valo

Sent: 10 February 2022 12:16

Qing Wang [off-list ref] writes:

quoted

From: Wang Qing <redacted>

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 <redacted>
---
 drivers/net/wireless/ath/wil6210/debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/ath/wil6210/debugfs.c b/drivers/net/wireless/ath/wil6210/debugfs.c
index 4c944e5..2cee9dd
--- a/drivers/net/wireless/ath/wil6210/debugfs.c
+++ b/drivers/net/wireless/ath/wil6210/debugfs.c

@@ -1766,7 +1766,7 @@ __acquires(&p->tid_rx_lock) __releases(&p->tid_rx_lock)
 			seq_puts(s, "\n");
 			if (!num_packets)
 				continue;
-			do_div(tx_latency_avg, num_packets);
+			div64_u64(tx_latency_avg, num_packets);

As you have been pointed out in your other patches, do_div() and
div64_u64() work differently.

And how long does it take for num_packets to exceed 2^32.

	David

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