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

[Xiangliang Yu]

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)

Thanks！
The current statement like this: child->linkrate = min(child_phy_linkrate, max(parent->max_linkrate, child_phy_linkrate->max_linkrate);

How about this change:
child->linkrate = min(parent->max_linkrate, child->max_linkrate);

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