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

Srivathsan Sivakumar
2022-06-09T19:39:56Z

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