Commit 36a43ea8 authored by Gabriel L. Somlo's avatar Gabriel L. Somlo Committed by Gerd Hoffmann
Browse files

fw_cfg: document ACPI device node information 



Signed-off-by: default avatarGabriel Somlo <somlo@cmu.edu>
Reviewed-by: default avatarLaszlo Ersek <lersek@redhat.com>
Reviewed-by: default avatarMarc Marí <markmb@redhat.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Message-id: 1455906029-25565-6-git-send-email-somlo@cmu.edu
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 70bee80d

docs/specs/fw_cfg.txt

+9 −0
Original line number Diff line number Diff line
@@ -84,6 +84,15 @@ Selector Register address: Base + 8 (2 bytes) 
Data Register address:     Base + 0 (8 bytes)

DMA Address address:       Base + 16 (8 bytes)



== ACPI Interface ==



The fw_cfg device is defined with ACPI ID "QEMU0002". Since we expect

ACPI tables to be passed into the guest through the fw_cfg device itself,

the guest-side firmware can not use ACPI to find fw_cfg. However, once the

firmware is finished setting up ACPI tables and hands control over to the

guest kernel, the latter can use the fw_cfg ACPI node for a more accurate

inventory of in-use IOport or MMIO regions.



== Firmware Configuration Items ==



=== Signature (Key 0x0000, FW_CFG_SIGNATURE) ===