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

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Date:	Wed, 21 May 2014 18:03:52 -0700
From:	Joe Perches <joe@...ches.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Fabian Frederick <fabf@...net.be>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kurt Garloff <garloff@...e.de>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/1] drivers/scsi/tmscsim.c: replace shift loop by ilog2

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@...e.de>
> > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > Signed-off-by: Fabian Frederick <fabf@...net.be>
> > > ---
> > >  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


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