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

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Date:   Tue, 12 Jul 2022 07:14:55 -0700
From:   Joe Perches <joe@...ches.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        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>,
        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 Tue, 2022-07-12 at 16:46 +0300, Dan Carpenter wrote:
> 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.

I think removing the multiply _improves_ readability.

> > diff --git 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.

Likely true.

> 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".

tmp is a poor name here.  Maybe dma would be better.

MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN) is also a poorly named macro
where all the existing uses are QLGE_BQ_LEN.

And there's base_indirect_ptr and base_indirect_dma in the struct
so just base_indirect might not be the best.

		tmp = (u64)rx_ring->lbq.base_dma;
		base_indirect_ptr = rx_ring->lbq.base_indirect;

And clarity is good.
Though here, clarity to value for effort though is dubious.

btw: this code got moved to staging 3 years ago.

Maybe it's getting closer to removal time.