linux-kernel - Re: [PATCH v3] staging: qlge: Fix indentation issue under long for loop

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Message-ID: <20220712134610.GO2338@kadam>
Date:   Tue, 12 Jul 2022 16:46:10 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Binyi Han <dantengknight@...il.com>
Cc:     Manish Chopra <manishc@...vell.com>, GR-Linux-NIC-Dev@...vell.com,
        Coiby Xu <coiby.xu@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>, netdev@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] staging: qlge: Fix indentation issue under long for
 loop

On Sun, Jul 10, 2022 at 02:04:18PM -0700, Binyi Han wrote:
> Fix indentation issue to adhere to Linux kernel coding style,
> Issue found by checkpatch. Change the long for loop into 3 lines. And
> optimize by avoiding the multiplication.

There is no possible way this optimization helps benchmarks.  Better to
focus on readability.

> 
> Signed-off-by: Binyi Han <dantengknight@...il.com>
> ---
> v2:
> 	- Change the long for loop into 3 lines.
> v3:
> 	- Align page_entries in the for loop to open parenthesis.
> 	- Optimize by avoiding the multiplication.
> 
>  drivers/staging/qlge/qlge_main.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/staging/qlge/qlge_main.c b/drivers/staging/qlge/qlge_main.c
> index 1a378330d775..4b166c66cfc5 100644
> --- a/drivers/staging/qlge/qlge_main.c
> +++ b/drivers/staging/qlge/qlge_main.c
> @@ -3007,10 +3007,12 @@ static int qlge_start_rx_ring(struct qlge_adapter *qdev, struct rx_ring *rx_ring
>  		tmp = (u64)rx_ring->lbq.base_dma;
>  		base_indirect_ptr = rx_ring->lbq.base_indirect;
>  
> -		for (page_entries = 0; page_entries <
> -			MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN); page_entries++)
> -				base_indirect_ptr[page_entries] =
> -					cpu_to_le64(tmp + (page_entries * DB_PAGE_SIZE));
> +		for (page_entries = 0;
> +		     page_entries < MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN);
> +		     page_entries++) {
> +			base_indirect_ptr[page_entries] = cpu_to_le64(tmp);
> +			tmp += DB_PAGE_SIZE;

I've previously said that using "int i;" is clearer here.  You would
kind of expect "page_entries" to be the number of entries, so it's kind
of misleading.  In other words, it's not just harmless wordiness and
needless exposition, it's actively bad.

I would probably just put it on one line:

		for (i = 0; i MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN); i++)
			base_indirect_ptr[i] = cpu_to_le64(tmp + (i * DB_PAGE_SIZE));

But if you want to break it up you could do:

		for (i = 0; i MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN); i++)
			base_indirect_ptr[i] = cpu_to_le64(tmp +
							   (i * DB_PAGE_SIZE));

"tmp" is kind of a bad name.  Also "base_indirect_ptr" would be better
as "base_indirect".

regards,
dan carpenter