Re: [PATCH 1/1] drivers/scsi/tmscsim.c: replace shift loop by ilog2
From: Fabian Frederick
Date: Thu May 22 2014 - 14:50:30 EST
On Wed, 21 May 2014 20:29:39 -0700
Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> 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
>
I wasn't aware of a problem with 0 value ... I guess we can forget
conversion here.
Fabian
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