netdev - Re: [net-next PATCH] amt: Use BIT macros instead of open codes

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Date:   Tue, 3 May 2022 18:28:36 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     Joe Perches <joe@...ches.com>, Paolo Abeni <pabeni@...hat.com>,
        Juhee Kang <claudiajkang@...il.com>, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org
Subject: Re: [net-next PATCH] amt: Use BIT macros instead of open codes

2022. 5. 3. 오전 2:19에 Joe Perches 이(가) 쓴 글:
 > On Mon, 2022-05-02 at 12:11 +0200, Paolo Abeni wrote:

Hi Paolo and Joe,
Thanks a lot for the reviews!

 >> On Sat, 2022-04-30 at 13:56 +0000, Juhee Kang wrote:
 >>> Replace open code related to bit operation with BIT macros, which 
kernel
 >>> provided. This patch provides no functional change.
 > []
 >>> diff --git a/drivers/net/amt.c b/drivers/net/amt.c
 > []
 >>> @@ -959,7 +959,7 @@ static void amt_req_work(struct work_struct *work)
 >>>   	amt_update_gw_status(amt, AMT_STATUS_SENT_REQUEST, true);
 >>>   	spin_lock_bh(&amt->lock);
 >>>   out:
 >>> -	exp = min_t(u32, (1 * (1 << amt->req_cnt)), AMT_MAX_REQ_TIMEOUT);
 >>> +	exp = min_t(u32, (1 * BIT(amt->req_cnt)), AMT_MAX_REQ_TIMEOUT);
 >>>   	mod_delayed_work(amt_wq, &amt->req_wq, msecs_to_jiffies(exp * 
1000));
 >>>   	spin_unlock_bh(&amt->lock);
 >>>   }
 >>> diff --git a/include/net/amt.h b/include/net/amt.h
 > []
 >>> @@ -354,7 +354,7 @@ struct amt_dev {
 >>>   #define AMT_MAX_GROUP		32
 >>>   #define AMT_MAX_SOURCE		128
 >>>   #define AMT_HSIZE_SHIFT		8
 >>> -#define AMT_HSIZE		(1 << AMT_HSIZE_SHIFT)
 >>> +#define AMT_HSIZE		BIT(AMT_HSIZE_SHIFT)
 >>>
 >>>   #define AMT_DISCOVERY_TIMEOUT	5000
 >>>   #define AMT_INIT_REQ_TIMEOUT	1
 >>
 >> Even if the 2 replaced statements use shift operations, they do not
 >> look like bit manipulation: the first one is an exponential timeout,
 >> the 2nd one is an (hash) size. I think using the BIT() macro here will
 >> be confusing.
 >
 > I agree.
 >
 > I also believe one of the uses of amt->req_cnt is error prone.
 >
 > 	drivers/net/amt.c:946:  if (amt->req_cnt++ > AMT_MAX_REQ_COUNT) {
 >
 > Combining a test and post increment is not a great style IMO.
 > Is this really the intended behavior?

I agree that it would be better to avoid that style.
I will send a patch for that after some bugfix.

Thanks a lot,
Taehee Yoo

 >
 >