Hi all,
If I understand the issue correctly, I don't quite agree that UEFI spec is
imprecise about SNP constraints described as following.
The "constraint" described here is that the grub should use attribute
"EXCLUSIVE" to open SNP protocol to gain exclusive access. This usage is clearly
described in page 184, chapter 6.3 EFI_BOOT_SERVICES.OpenProtocol().
EXCLUSIVE Used by applications to gain exclusive access to a
protocol interface.
If any drivers have the protocol interface opened with
an attribute of BY_DRIVER,
then an attempt will be made to remove them by calling
the driver's Stop() function.
The grub code should not assume that the SNP is not occupied by other drivers,
instead, it should use EXCLUSIVE to open SNP protocol, or to be more precise,
use OpenProtocolInformation() to check whether SNP is already opened by other
driver, then decide whether need to use EXCLUSIVE to disconnect the other
drivers. This is the typical usage for all UEFI protocol, not particular
constraints to SNP protocol.