netdev - [PATCH] staging: qlge: qlge_main.c: convert do-while loops to for loops

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Message-ID: <YqJMieQ3Hf8qc6nj@Sassy>
Date:   Thu, 9 Jun 2022 15:39:53 -0400
From:   Srivathsan Sivakumar <sri.skumar05@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.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: [PATCH] staging: qlge: qlge_main.c: convert do-while loops to for
 loops

On Thu, Jun 09, 2022 at 09:34:19PM +0300, Dan Carpenter wrote:
> On Thu, Jun 09, 2022 at 01:01:27PM -0400, Srivathsan Sivakumar wrote:
> > On Thu, Jun 09, 2022 at 06:26:53PM +0300, Dan Carpenter wrote:
> > > On Thu, Jun 09, 2022 at 11:15:51AM -0400, Srivathsan Sivakumar wrote:
> > > > diff --git a/drivers/staging/qlge/qlge_main.c b/drivers/staging/qlge/qlge_main.c
> > > > index 8c35d4c4b851..308e8b621185 100644
> > > > --- a/drivers/staging/qlge/qlge_main.c
> > > > +++ b/drivers/staging/qlge/qlge_main.c
> > > > @@ -3006,13 +3006,13 @@ static int qlge_start_rx_ring(struct qlge_adapter *qdev, struct rx_ring *rx_ring
> > > >  		cqicb->flags |= FLAGS_LL;	/* Load lbq values */
> > > >  		tmp = (u64)rx_ring->lbq.base_dma;
> > > >  		base_indirect_ptr = rx_ring->lbq.base_indirect;
> > > > -		page_entries = 0;
> > > > -		do {
> > > > -			*base_indirect_ptr = cpu_to_le64(tmp);
> > > > -			tmp += DB_PAGE_SIZE;
> > > > -			base_indirect_ptr++;
> > > > -			page_entries++;
> > > > -		} while (page_entries < MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN));
> > > > +
> > > > +		for (page_entries = 0; page_entries <
> > > > +			MAX_DB_PAGES_PER_BQ(QLGE_BQ_LEN); page_entries++) {
> > > > +				*base_indirect_ptr = cpu_to_le64(tmp);
> > > > +				tmp += DB_PAGE_SIZE;
> > > > +				base_indirect_ptr++;
> > > > +		}
> > > 
> > > It's better than the original, but wouldn't it be better yet to write
> > > something like this (untested):
> > > 
> > > 		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));
> > > 
> > > Same with the other as well, obviously.
> > > 
> > > regards,
> > > dan carpenter
> > > 
> > 
> > Hello Dan,
> > 
> > Thanks for your input
> > 
> > wouldn't base_indirect_ptr point at a different endian value if tmp is
> > added with (i * DB_PAGE_SIZE)?
> 
> tmp is cpu endian so we can do math on it.  Then we convert the result
> to le64.  This is how it works before and after.  What isn't allowed
> (doesn't make sense) is to do math on endian data so "cpu_to_le64(tmp) +
> i * DB_PAGE_SIZE" is wrong.
> 
> Sparse can detect endian bugs like that:
> https://lwn.net/Articles/205624/
> 
> regards,
> dan carpenter
>

I understand now, I'll send the revised patch soon

thanks, 
Srivathsan