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

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

[Fabian Frederick]

Cc: Kurt Garloff <garloff@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.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
index b006cf7..c353848 100644
--- 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");
-- 
1.8.4.5

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

[Joe Perches]

On Tue, 2014-05-20 at 18:48 +0200, Fabian Frederick wrote:
> Cc: Kurt Garloff <garloff@suse.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Fabian Frederick <fabf@skynet.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>?

If so, that should be mentioned in the changelog.

These should probably add #include <linux/log2.h>

It would have been nicer to use a patch series
and a cover letter so I could make this reply to
to cover letter.

Please take the time to setup and use git send-email
instead of sylpheed.

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

[Fabian Frederick]

On Tue, 20 May 2014 10:06:42 -0700
Joe Perches <joe@perches.com> wrote:

> On Tue, 2014-05-20 at 18:48 +0200, Fabian Frederick wrote:
> > Cc: Kurt Garloff <garloff@suse.de>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Fabian Frederick <fabf@skynet.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>?
> 
> If so, that should be mentioned in the changelog.
> 
> These should probably add #include <linux/log2.h>
> 
> It would have been nicer to use a patch series
> and a cover letter so I could make this reply to
> to cover letter.
> 
> Please take the time to setup and use git send-email
> instead of sylpheed.
> 
Hello Joe,

   Ok, I'll send a new version in patchset mode.

Fabian

> 

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

[Guenter Roeck]

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@suse.de>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Signed-off-by: Fabian Frederick <fabf@skynet.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() ?

Guenter

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

[Joe Perches]

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@suse.de>
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > Signed-off-by: Fabian Frederick <fabf@skynet.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

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@suse.de>
>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>> Signed-off-by: Fabian Frederick <fabf@skynet.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
>

:-).

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

Guenter

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

[Fabian Frederick]

On Wed, 21 May 2014 20:29:39 -0700
Guenter Roeck <linux@roeck-us.net> 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@suse.de>
> >>>> Cc: Andrew Morton <akpm@linux-foundation.org>
> >>>> Signed-off-by: Fabian Frederick <fabf@skynet.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
> >
> 
> :-).
> 
> 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