On Sep 4, 2013, at 3:11 PM, "David F." <[email protected]> wrote:

> Hi,
> 
> So when a driver produces two protocol interfaces to access the device using 
> the same protocol GUID.  How do you open each instance?
> 

They are produced on different handles, as only a single protocol GUID can 
exist per handle. 

> Say you look for all BlkIo protocol devices via HandleBuffer, then want to 
> look if an ATA or SCSI passthru is attached as well, so use same handle, but 
> ATA pass-through could have multiple interfaces logical/physical ...  how do 
> you parse through those?

You can read about SCSI Pass Thru in UEFI 2.4 sections 14.1 and 14.2. The Pass 
Through driver sits on the handle the represents the device, and it is a bus 
driver that produces child handles with EFI_SCSI_IO_PROTOCOL on them that 
represent SCSI targets. So the child handles will have the device path of the 
parent, with a SCSI device path appended to identify the targets. 

Thanks,

Andrew Fish

> 
> TIA!!
> 
> 
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