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Date:   Wed, 15 Jul 2020 07:30:32 +0100
From:   Lee Jones <lee.jones@linaro.org>
To:     Hannes Reinecke <hare@suse.de>
Cc:     James Bottomley <jejb@linux.ibm.com>, martin.petersen@oracle.com,
        linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
        Hannes Reinecke <hare@suse.com>
Subject: Re: [PATCH v2 24/24] scsi: aic7xxx: aic79xx_osm: Remove set but
 unused variabes 'saved_scsiid' and 'saved_modes'
Message-ID: <20200715063032.GN1398296@dell>
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On Wed, 15 Jul 2020, Hannes Reinecke wrote:

> On 7/14/20 11:39 PM, Lee Jones wrote:
> > On Tue, 14 Jul 2020, James Bottomley wrote:
> > 
> > > On Tue, 2020-07-14 at 09:46 +0200, Hannes Reinecke wrote:
> > > > On 7/13/20 10:00 AM, Lee Jones wrote:
> > > > > Haven't been used since 2006.
> > > > > 
> > > > > Fixes the following W=1 kernel build warning(s):
> > > > > 
> > > > >   drivers/scsi/aic7xxx/aic79xx_osm.c: In function
> > > > > ‘ahd_linux_queue_abort_cmd’:
> > > > >   drivers/scsi/aic7xxx/aic79xx_osm.c:2155:17: warning: variable
> > > > > ‘saved_modes’ set but not used [-Wunused-but-set-variable]
> > > > >   drivers/scsi/aic7xxx/aic79xx_osm.c:2148:9: warning: variable
> > > > > ‘saved_scsiid’ set but not used [-Wunused-but-set-variable]
> > > > > 
> > > > > Cc: Hannes Reinecke <hare@suse.com>
> > > > > Signed-off-by: Lee Jones <lee.jones@linaro.org>
> > > > > ---
> > > > >   drivers/scsi/aic7xxx/aic79xx_osm.c | 4 ----
> > > > >   1 file changed, 4 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/scsi/aic7xxx/aic79xx_osm.c
> > > > > b/drivers/scsi/aic7xxx/aic79xx_osm.c
> > > > > index 3782a20d58885..140c4e74ddd7e 100644
> > > > > --- a/drivers/scsi/aic7xxx/aic79xx_osm.c
> > > > > +++ b/drivers/scsi/aic7xxx/aic79xx_osm.c
> > > > > @@ -2141,14 +2141,12 @@ ahd_linux_queue_abort_cmd(struct scsi_cmnd
> > > > > *cmd)
> > > > >   	u_int  saved_scbptr;
> > > > >   	u_int  active_scbptr;
> > > > >   	u_int  last_phase;
> > > > > -	u_int  saved_scsiid;
> > > > >   	u_int  cdb_byte;
> > > > >   	int    retval;
> > > > >   	int    was_paused;
> > > > >   	int    paused;
> > > > >   	int    wait;
> > > > >   	int    disconnected;
> > > > > -	ahd_mode_state saved_modes;
> > > > >   	unsigned long flags;
> > > > >   	pending_scb = NULL;
> > > > > @@ -2239,7 +2237,6 @@ ahd_linux_queue_abort_cmd(struct scsi_cmnd
> > > > > *cmd)
> > > > >   		goto done;
> > > > >   	}
> > > > > -	saved_modes = ahd_save_modes(ahd);
> > > > >   	ahd_set_modes(ahd, AHD_MODE_SCSI, AHD_MODE_SCSI);
> > > > >   	last_phase = ahd_inb(ahd, LASTPHASE);
> > > > >   	saved_scbptr = ahd_get_scbptr(ahd);
> > > > > @@ -2257,7 +2254,6 @@ ahd_linux_queue_abort_cmd(struct scsi_cmnd
> > > > > *cmd)
> > > > >   	 * passed in command.  That command is currently active on
> > > > > the
> > > > >   	 * bus or is in the disconnected state.
> > > > >   	 */
> > > > > -	saved_scsiid = ahd_inb(ahd, SAVED_SCSIID);
> > > > >   	if (last_phase != P_BUSFREE
> > > > >   	    && SCB_GET_TAG(pending_scb) == active_scbptr) {
> > > > > 
> > > > 
> > > > Reviewed-by: Hannes Reinecke <hare@suse.de>
> > > 
> > > Hey, you don't get to do that ... I asked you to figure out why we're
> > > missing an ahd_restore_modes().  Removing the ahd_save_modes() is
> > > cosmetic: it gets rid of a warning but doesn't fix the problem.  I'd
> > > rather keep the warning until the problem is fixed and the problem is
> > > we need a mode save/restore around the ahd_set_modes() which is only
> > > partially implemented in this function.
> > 
> > I had a look.  Traced it back to the dawn of time (time == Git), then
> > delved even further back by downloading and trawling through ~10-15
> > tarballs.  It looks as though drivers/scsi/aic7xxx/aic79xx_osm.c was
> > upstreamed in v2.5.60, nearly 20 years ago.  'saved_modes' has been
> > unused since at least then.  If no one has complained in 2 decades,
> > I'd say it probably isn't an issue worth perusing.
> > 
> That's not really the point; this function is the first stage of error
> recovery. And the only real way of exercising this is to inject a command
> timeout, which is nearly impossible without dedicated hardware.
> So this function will have a very limited exposure, but nevertheless a quite
> crucial function.
> Hence I'm not quite agree with your reasoning, and rather would have it
> fixed.

100% agree.

> But as we're having an alternative fix now, it might be best if you could
> drop it from your patchset and we'll fix it separately.

Sounds good.  Thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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