20.3.1 Driver Binding Protocol Supported()

SCSI device drivers and must implement the EFI_DRIVER_BINDING_PROTOCOL that contains the Supported(), Start(), and Stop() services. The Supported() service checks the controller handle that has been passed in to see whether this handle represents a SCSI device that this driver knows how to manage.

The following is the most common method for doing the check:

• Check if this handle has EFI_SCSI_IO_PROTOCOL installed. If not, this handle is not a SCSI device on the current SCSI channel.
• Retrieve the 8-bit SCSI device type to see if the type is one that this driver can manage.

If the above two checks are passed, it means that the SCSI device driver can manage the device that the controller handle represents. The Supported() service returns EFI_SUCCESS. Otherwise, the Supported() service returns EFI_UNSUPPORTED. In addition, this check process must not disturb the current state of the SCSI device, because a another SCSI device driver may be managing this SCSI device.

The following example shows an implementation of the Driver Binding Protocol Supported() service for a SCSI mass storage device. It opens the SCSI I/O Protocol with an attribute of EFI_OPEN_PROTOCOL_BY_DRIVER. It then used the GetDeviceType() service of the SCSI I/O Protocol and evaluates the type information to see if it is a hard drive or a CD-ROM.

Example 219-Supported() for a SCSI device driver

#include <Uefi.h>
#include <Protocol/DriverBinding.h> #include <Protocol/ScsiIo.h>
#include <IndustryStandard/Scsi.h>
#include <Library/UefiBootServicesTableLib.h>

EFI_STATUS
EFIAPI
AbcSupported (
  IN EFI_DRIVER_BINDING_PROTOCOL  *This,
  IN EFI_HANDLE                   ControllerHandle,
  IN EFI_DEVICE_PATH_PROTOCOL     *RemainingDevicePath   OPTIONAL
  )
{
  EFI_STATUS            Status;
  EFI_SCSI_IO_PROTOCOL  *ScsiIo;
  UINT8                 DeviceType;

  //
  // Open the SCSI I/O Protocol on ControllerHandle
  //
  Status = gBS->OpenProtocol (
                  ControllerHandle,
                  &gEfiScsiIoProtocolGuid,
                  (VOID **)&ScsiIo,
                  This->DriverBindingHandle,
                  ControllerHandle,
                  EFI_OPEN_PROTOCOL_BY_DRIVER
                  );
  if (EFI_ERROR (Status)) {
    return Status;
  }

  //
  // Get the SCSI Device Type
  //
  Status = ScsiIo->GetDeviceType (ScsiIo, &DeviceType);
  if (EFI_ERROR (Status)) {
    goto Done;
  }

  //
  // Check to see if the interface descriptor is supported by this driver
  //
  if ((DeviceType != EFI_SCSI_TYPE_DISK ) && (DeviceType != EFI_SCSI_TYPE_CDROM) ) {
    Status = EFI_UNSUPPORTED;
  }

Done:
  //
  // Close the SCSI I/O Protocol
  //
  gBS->CloseProtocol (
         ControllerHandle,
         &gEfiScsiIoProtocolGuid,
         This->DriverBindingHandle,
         ControllerHandle
         );

  return Status;
}