Re: [PATCH 1/1] drivers/scsi/tmscsim.c: replace shift loop by ilog2

[Guenter Roeck]

On 05/21/2014 06:03 PM, Joe Perches wrote:
> On Wed, 2014-05-21 at 17:28 -0700, Guenter Roeck wrote:
> > On Tue, May 20, 2014 at 10:06:42AM -0700, Joe Perches wrote:
> > > On Tue, 2014-05-20 at 18:48 +0200, Fabian Frederick wrote:
> > > > Cc: Kurt Garloff <garloff@xxxxxxx>
> > > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > > > Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
> > > > ---
> > > >   drivers/scsi/tmscsim.c | 2 +-
> > > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/scsi/tmscsim.c b/drivers/scsi/tmscsim.c
> > > []
> > > > @@ -1611,7 +1611,7 @@ dc390_Reselect( struct dc390_acb* pACB )
> > > >         printk (KERN_ERR "DC390: Reselection must select host adapter: %02x!\n", lun);
> > > >       else
> > > >         lun ^= 1 << pACB->pScsiHost->this_id; /* Mask AdapterID */
> > > > -    id = 0; while (lun >>= 1) id++;
> > > > +    id = ilog2(lun);
> > > >       /* Get LUN */
> > > >       lun = DC390_read8 (ScsiFifo);
> > > >       if (!(lun & IDENTIFY_BASE)) printk (KERN_ERR "DC390: Resel: Expect identify message!\n");
> > >
> > > Hey Fabian.
> > >
> > > You've submitted several of these now.
> > >
> > > Have you gone through all of these to make sure
> > > that the ilog2(<foo>) uses are always using a
> > > non-zero <foo>?
> > Maybe I am missing something. Why not just use fls() ?
>
> fls strains Andrew Morton's brain.
>
> https://lkml.org/lkml/2014/5/19/771

:-).

On the other side fls(1) == 1 while ilog2(1) == 0. So some test is necessary anyway.

Guenter

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