Re: [PATCH] [SCSI] LIBSAS: fix libsas link error issue

[Douglas Gilbert]

On 11-06-14 09:44 PM, Xiangliang Yu wrote:
> Subject: Re: [PATCH] [SCSI] LIBSAS: fix libsas link error issue
>
> On Tue, 2011-06-14 at 23:17 +0800, yxlraid@xxxxxxxxx wrote:
> > > From: Xiangliang Yu<yuxiangl@xxxxxxxxxxx>
> > >
> > > -- The value of child link rate should is minimum of link rate, or
> > >     command will fail if child link rate is bigger than parent link rate.
> > >
> > > Signed-off-by: Xiangliang Yu<yuxiangl@xxxxxxxxxxx>
> > > ---
> > >   drivers/scsi/libsas/sas_expander.c |    2 +-
> > >   1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> > > index 874e29d..6ccca09 100644
> > > --- a/drivers/scsi/libsas/sas_expander.c
> > > +++ b/drivers/scsi/libsas/sas_expander.c
> > > @@ -638,7 +638,7 @@ static void sas_ex_get_linkrate(struct domain_device *parent,
> > >   			sas_port_add_phy(port, phy->phy);
> > >   		}
> > >   	}
> > > -	child->linkrate = min(parent_phy->linkrate, child->max_linkrate);
> > > +	child->linkrate = min(parent_phy->linkrate, child->min_linkrate);
>
> > This patch doesn't look right.  It will clamp the phy to the minim
> > possible link rate.
> Link negotiation should get the minimum.

spl2r01.pdf [Most recent SAS-3 draft for the protocol layers]

5.7.4.2.1 SAS speed negotiation sequence overview

"The SAS speed negotiation sequence establishes communications between
the two phys on a physical link at the highest possible transmission
rate."


That seems to suggest:
   min(<one_end>.max_linkrate, <other_end>.max_linkrate)

Doug Gilbert


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