dev nodes assignement ?

dev nodes assignement ?

[devnetfs]

Hello,

Is /dev/sdX scsi dev node assignment based *only* on the pci-slot
the HBA's are in? or also upon the order in which the LLDD is loaded?

In other words does the mid-layer scan+make-a-list of all HBA's on
the system (and thereby assigning the /dev name) and then when a LLDD
is loaded, tells it the HBA-list? 
OR
Does each LLDD does a pci-scan and assign /dev name for HBA's that it
can handle -- in which case the order of LLDD getting loaded is also
important in deciding the /dev/sdX name.

Please clarify, 
Thanks in advance
A.

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Re: dev nodes assignement ?

[Steven Dake]

first come first serve.  devfs defines the device nodes using access 
path (host/channel/id/lun) which is a bit more usable for hotswap 
situtations, assuming your id's don't change.

Thanks
-steve

devnetfs wrote:

>Hello,
>
>Is /dev/sdX scsi dev node assignment based *only* on the pci-slot
>the HBA's are in? or also upon the order in which the LLDD is loaded?
>
>In other words does the mid-layer scan+make-a-list of all HBA's on
>the system (and thereby assigning the /dev name) and then when a LLDD
>is loaded, tells it the HBA-list? 
>OR
>Does each LLDD does a pci-scan and assign /dev name for HBA's that it
>can handle -- in which case the order of LLDD getting loaded is also
>important in deciding the /dev/sdX name.
>
>Please clarify, 
>Thanks in advance
>A.
>
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>
>
>  
>

Re: dev nodes assignement ?

[Bryan Henderson]

>Is /dev/sdX scsi dev node assignment based *only* on the pci-slot
>the HBA's are in? or also upon the order in which the LLDD is loaded?

First of all, let's acknowledge that the /dev/sdX device special file
assignments are done manually by the user and are permanent.  /dev/sdX is
assigned to a major and minor number.

So the actual question is about minor number assignments.

>... OR
>Does each LLDD do a pci-scan and assign [minor numbers] for HBA's that it
>can handle -- in which case the order of LLDD getting loaded is also
>important in deciding the [minor number].

Yes.

Re: dev nodes assignement ?

[devnetfs]

Thanks Bryan and Steve for clarifying my (long standing) doubt :)

Regards,
A.

--- Bryan Henderson <hbryan@us.ibm.com> wrote:
> >Is /dev/sdX scsi dev node assignment based *only* on the pci-slot
> >the HBA's are in? or also upon the order in which the LLDD isloaded?
> 
> First of all, let's acknowledge that the /dev/sdX device special file
> assignments are done manually by the user and are permanent. 
> /dev/sdX is assigned to a major and minor number.
> 
> So the actual question is about minor number assignments.
> >... OR
> >Does each LLDD do a pci-scan and assign [minor numbers] for HBA's
> >that it can handle -- in which case the order of LLDD getting 
> > loaded is alsoimportant in deciding the [minor number].
> Yes.


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