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[Qemu-arm] [PATCH v7 5/5] fw_cfg: document ACPI device node information
From: |
Gabriel L. Somlo |
Subject: |
[Qemu-arm] [PATCH v7 5/5] fw_cfg: document ACPI device node information |
Date: |
Wed, 10 Feb 2016 15:41:40 -0500 |
Signed-off-by: Gabriel Somlo <address@hidden>
Reviewed-by: Laszlo Ersek <address@hidden>
Reviewed-by: Marc MarĂ <address@hidden>
---
docs/specs/fw_cfg.txt | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 2099ad9..5414140 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -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) ===
--
2.4.3