Re: [patch 13/17] scsi: remove private implementation of get_unaligned_be32

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2008-10-29 at 15:07 -0700, Andrew Morton wrote:
> On Wed, 29 Oct 2008 16:48:14 -0500
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > On Wed, 2008-10-29 at 14:24 -0700, akpm@linux-foundation.org wrote:
> > > From: Harvey Harrison <harvey.harrison@gmail.com>
> > > 
> > > Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
> > > Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
> > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > > ---
> > > 
> > >  drivers/scsi/libsas/sas_expander.c |    9 +++++----
> > >  include/scsi/scsi.h                |    6 ------
> > >  2 files changed, 5 insertions(+), 10 deletions(-)
> > > 
> > > diff -puN drivers/scsi/libsas/sas_expander.c~scsi-remove-private-implementation-of-get_unaligned_be32 drivers/scsi/libsas/sas_expander.c
> > > --- a/drivers/scsi/libsas/sas_expander.c~scsi-remove-private-implementation-of-get_unaligned_be32
> > > +++ a/drivers/scsi/libsas/sas_expander.c
> > > @@ -24,6 +24,7 @@
> > >  
> > >  #include <linux/scatterlist.h>
> > >  #include <linux/blkdev.h>
> > > +#include <asm/unaligned.h>
> > >  
> > >  #include "sas_internal.h"
> > >  
> > > @@ -541,10 +542,10 @@ int sas_smp_get_phy_events(struct sas_ph
> > >  	if (!res)
> > >  		goto out;
> > >  
> > > -	phy->invalid_dword_count = scsi_to_u32(&resp[12]);
> > > -	phy->running_disparity_error_count = scsi_to_u32(&resp[16]);
> > > -	phy->loss_of_dword_sync_count = scsi_to_u32(&resp[20]);
> > > -	phy->phy_reset_problem_count = scsi_to_u32(&resp[24]);
> > > +	phy->invalid_dword_count = get_unaligned_be32(&resp[12]);
> > > +	phy->running_disparity_error_count = get_unaligned_be32(&resp[16]);
> > > +	phy->loss_of_dword_sync_count = get_unaligned_be32(&resp[20]);
> > > +	phy->phy_reset_problem_count = get_unaligned_be32(&resp[24]);
> > >  
> > >   out:
> > >  	kfree(resp);
> > > diff -puN include/scsi/scsi.h~scsi-remove-private-implementation-of-get_unaligned_be32 include/scsi/scsi.h
> > > --- a/include/scsi/scsi.h~scsi-remove-private-implementation-of-get_unaligned_be32
> > > +++ a/include/scsi/scsi.h
> > > @@ -527,10 +527,4 @@ static inline void set_driver_byte(struc
> > >  /* Used to obtain the PCI location of a device */
> > >  #define SCSI_IOCTL_GET_PCI		0x5387
> > >  
> > > -/* Pull a u32 out of a SCSI message (using BE SCSI conventions) */
> > > -static inline __u32 scsi_to_u32(__u8 *ptr)
> > > -{
> > > -	return (ptr[0]<<24) + (ptr[1]<<16) + (ptr[2]<<8) + ptr[3];
> > > -}
> > > -
> > >  #endif /* _SCSI_SCSI_H */
> > 
> > No ... as I've said several times now, there's a debate going on about
> > what we're supposed to be doing with all of this (either putting it in
> > SCSI, pulling it out or just using the inline notation.
> 
> If I knew what the terrible word "it" is replacing, I'd know what the
> above sentence means.

It being the correct way to handle multibyte SCSI problems.

> I'm kinda struggling to imagine why there's controversy, really.  scsi
> has a private implementation of something which core kernel provides. 
> Zap!

The main problems with the above are that a lot of people don't
necessarily think Big Endian when they see SCSI (even though it's a BE
bus), so the get_unaligned_beXX looks strange, and secondly most of the
arrays we operate on are simple u8 ones, so sparse gets annoyed about
sending a non BE quantity through a BE conversion ... I bet it even does
this for the above patch.

> >  I'm not putting
> > a patch like this in until we at least get some consensus.
> 
> I'll hang onto it, so there's nowhere to hide...

OK.

James