20.1.8 SCSI Device Path
The SCSI host controller driver described in this document support a SCSI channel that is generated or emulated by multiple architectures, such as SCSI-I, SCSI-II, SCSI-III, ATAPI, Fibre Channel, iSCSI, and other future channel types. This section describes four example device paths, including SCSI, ATAPI, and Fibre Channel device paths.
The table below shows an example device path for a SCSI host controller that supports a single SCSI channel and is located at PCI device number 0x07 and PCI function 0x00 The PCI SCSI host controller is directly attached to a PCI root bridge.
This sample device path consists of an ACPI device path node, a PCI device path node, and a device path end structure. The _HID and _UID must match the ACPI table description of the PCI root bridge. The following is the shorthand notation for this device path: ACPI(PNP0A03,0)/PCI(7|0).
Byte offset | Byte length | Data | Description |
0x00 | 0x01 | 0x02 | Generic Device Path Header - Type ACPI Device Path |
0x01 | 0x01 | 0x01 | Sub type - ACPI Device Path |
0x02 | 0x02 | 0x0C | Length - 0x0C bytes |
0x04 | 0x04 | 0x41D0, | _HID PNP0A03 - 0x41D0 represents a compressed string 'PNP' and is in the low-order bytes. |
| | 0x0A03 | |
0x08 | 0x04 | 0x0000 | _UID |
0x0C | 0x01 | 0x01 | Generic Device Path Header - Type Hardware Device Path |
0x0D | 0x01 | 0x01 | Sub type - PCI |
0x0E | 0x02 | 0x06 | Length - 0x06 bytes |
0x10 | 0x01 | 0x07 | PCI Function |
0x11 | 0x01 | 0x00 | PCI Device |
0x12 | 0x01 | 0xFF | Generic Device Path Header - Type End of Hardware Device Path |
0x13 | 0x01 | 0xFF | Sub type - End of Entire Device Path |
0x14 | 0x02 | 0x04 | Length - 0x04 bytes |
A SCSI host controller with multiple SCSI channels on a multi-function PCI controller only changes the PCI portion of the device path for each SCII channel. In this example, SCSI channel 0 is accessed through PCI function #0, and SCSI channel 1 is accessed through PCI function #1 The following are the device paths for these SCSI channels:
ACPI(PNP0A03,1)/PCI(7|0)- Access to channel 0ACPI(PNP0A03,1)/PCI(7|1)Access to channel 1
If there is a SCSI PCI controller with multiple SCSI channels connected to a single-function PCI device, the device paths must differentiate the SCSI channels. In this example, SCSI channel 0 is accessed through Controller #0 below PCI function #0, and SCSI channel 1 is accessed through Controller #1 below PCI function #1. The following are the device paths for these SCSI channels:
ACPI(PNP0A03,1)/PCI(7|0)/Controller(0)- Access to channel 0ACPI(PNP0A03,1)/PCI(7|0)/Controller(1)- Access to channel 1
If a SCSI driver supports both blocking and non-blocking I/O modes, any client of the SCSI driver can use them to perform SCSI I/O.
The following example demonstrates how to use Extended SCSI Pass Thru Protocol to perform blocking and non-blocking I/O.
#include <Uefi.h>
#include <Protocol/ScsiPassThruExt.h>
#include <Library/UefiBootServicesTableLib.h>
EFI_STATUS
EFIAPI
ScsiPassThruTests (
EFI_EXT_SCSI_PASS_THRU_PROTOCOL *ScsiPassThru,
UINT8 *Target,
UINT64 Lun
)
{
EFI_STATUS Status;
EFI_EXT_SCSI_PASS_THRU_SCSI_REQUEST_PACKET Packet;
EFI_EVENT
Event;
//
// Fill in Packet for the requested test operation
//
//
// Blocking I/O
//
Status = ScsiPassThru->PassThru (
ScsiPassThru,
Target,
Lun,
&Packet,
NULL
);
//
// Non Blocking I/O
//
Status = gBS->CreateEvent (
EVT_NOTIFY_SIGNAL,
TPL_CALLBACK,
NULL,
NULL,
&Event
);
Status = ScsiPassThru->PassThru (
ScsiPassThru,
Target,
Lun,
&Packet,
&Event
);
do {
Status = gBS->CheckEvent (Event);
} while (EFI_ERROR (Status));
return Status;
}
Last modified 2yr ago