tpm_crb is a device for TPM 2.0 Command Response Buffer (CRB)
Interface as defined in TCG PC Client Platform TPM Profile (PTP)
Specification Family “2.0” Level 00 Revision 01.03 v22.
The PTP allows device implementation to switch between TIS and CRB
model at run time, but given that CRB is a simpler device to
implement, I chose to implement it as a different device.
The device doesn't implement other locality than 0 for now (my laptop
TPM doesn't either, so I assume this isn't so bad)
The command/reply memory region is statically allocated after the CRB
registers address TPM_CRB_ADDR_BASE + sizeof(struct crb_regs) (I
wonder if the BIOS could or should allocate it instead, or what size
to use, again this seems to fit well expectations)
The PTP doesn't specify a particular bus to put the device. So I added
it on the system bus directly, so it could hopefully be used easily on
a different platform than x86. Currently, it fails to init on piix,
because error_on_sysbus_device() check. The check may be changed in a
near future, see discussion on the qemu-devel ML.