From 8fd108804224c6161ee9b551ba49ac91f928b446 Mon Sep 17 00:00:00 2001
From: Ben Widawsky <bwidawsk@FreeBSD.org>
Date: Mon, 22 Oct 2018 03:29:54 +0000
Subject: [PATCH] acpi: Add an interface to obtain DSM information

The Device Specific Method (_DSM) is on optional object that defines
device specific controls. This will be useful for our power management
controller in upcoming patches. More information can be found in ACPI
spec 6.2 section 9.1.1

https://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf

This patch had a minor modification changing ENOMEM to AE_NO_MEMORY
after it got review and approval but before committing.

Test Plan: Tested in my s0ix branch

Reviewed by:	kib
Approved by:	emaste (mentor)
Differential Revision: https://reviews.freebsd.org/D17121
---
 sys/dev/acpica/acpi.c    | 92 ++++++++++++++++++++++++++++++++++++++++
 sys/dev/acpica/acpivar.h |  4 ++
 2 files changed, 96 insertions(+)

diff --git a/sys/dev/acpica/acpi.c b/sys/dev/acpica/acpi.c
index f55a0048e4b6..515370d55845 100644
--- a/sys/dev/acpica/acpi.c
+++ b/sys/dev/acpica/acpi.c
@@ -2570,6 +2570,98 @@ acpi_AppendBufferResource(ACPI_BUFFER *buf, ACPI_RESOURCE *res)
     return (AE_OK);
 }
 
+UINT8
+acpi_DSMQuery(ACPI_HANDLE h, uint8_t *uuid, int revision)
+{
+    /*
+     * ACPI spec 9.1.1 defines this.
+     *
+     * "Arg2: Function Index Represents a specific function whose meaning is
+     * specific to the UUID and Revision ID. Function indices should start
+     * with 1. Function number zero is a query function (see the special
+     * return code defined below)."
+     */
+    ACPI_BUFFER buf;
+    ACPI_OBJECT *obj;
+    UINT8 ret = 0;
+
+    if (!ACPI_SUCCESS(acpi_EvaluateDSM(h, uuid, revision, 0, NULL, &buf))) {
+	ACPI_INFO(("Failed to enumerate DSM functions\n"));
+	return (0);
+    }
+
+    obj = (ACPI_OBJECT *)buf.Pointer;
+    KASSERT(obj, ("Object not allowed to be NULL\n"));
+
+    /*
+     * From ACPI 6.2 spec 9.1.1:
+     * If Function Index = 0, a Buffer containing a function index bitfield.
+     * Otherwise, the return value and type depends on the UUID and revision
+     * ID (see below).
+     */
+    switch (obj->Type) {
+    case ACPI_TYPE_BUFFER:
+	ret = *(uint8_t *)obj->Buffer.Pointer;
+	break;
+    case ACPI_TYPE_INTEGER:
+	ACPI_BIOS_WARNING((AE_INFO,
+	    "Possibly buggy BIOS with ACPI_TYPE_INTEGER for function enumeration\n"));
+	ret = obj->Integer.Value & 0xFF;
+	break;
+    default:
+	ACPI_WARNING((AE_INFO, "Unexpected return type %u\n", obj->Type));
+    };
+
+    AcpiOsFree(obj);
+    return ret;
+}
+
+/*
+ * DSM may return multiple types depending on the function. It is therefore
+ * unsafe to use the typed evaluation. It is highly recommended that the caller
+ * check the type of the returned object.
+ */
+ACPI_STATUS
+acpi_EvaluateDSM(ACPI_HANDLE handle, uint8_t *uuid, int revision,
+    uint64_t function, union acpi_object *package, ACPI_BUFFER *out_buf)
+{
+    ACPI_OBJECT arg[4];
+    ACPI_OBJECT_LIST arglist;
+    ACPI_BUFFER buf;
+    ACPI_STATUS status;
+
+    if (out_buf == NULL)
+	return (AE_NO_MEMORY);
+
+    arg[0].Type = ACPI_TYPE_BUFFER;
+    arg[0].Buffer.Length = ACPI_UUID_LENGTH;
+    arg[0].Buffer.Pointer = uuid;
+    arg[1].Type = ACPI_TYPE_INTEGER;
+    arg[1].Integer.Value = revision;
+    arg[2].Type = ACPI_TYPE_INTEGER;
+    arg[2].Integer.Value = function;
+    if (package) {
+	arg[3] = *package;
+    } else {
+	arg[3].Type = ACPI_TYPE_PACKAGE;
+	arg[3].Package.Count = 0;
+	arg[3].Package.Elements = NULL;
+    }
+
+    arglist.Pointer = arg;
+    arglist.Count = 4;
+    buf.Pointer = NULL;
+    buf.Length = ACPI_ALLOCATE_BUFFER;
+    status = AcpiEvaluateObject(handle, "_DSM", &arglist, &buf);
+    if (ACPI_FAILURE(status))
+	return (status);
+
+    KASSERT(ACPI_SUCCESS(status), ("Unexpected status"));
+
+    *out_buf = buf;
+    return (status);
+}
+
 ACPI_STATUS
 acpi_EvaluateOSC(ACPI_HANDLE handle, uint8_t *uuid, int revision, int count,
     uint32_t *caps_in, uint32_t *caps_out, bool query)
diff --git a/sys/dev/acpica/acpivar.h b/sys/dev/acpica/acpivar.h
index 989f2be1c4b7..7e0f6cebd5fc 100644
--- a/sys/dev/acpica/acpivar.h
+++ b/sys/dev/acpica/acpivar.h
@@ -349,6 +349,10 @@ ACPI_STATUS	acpi_FindIndexedResource(ACPI_BUFFER *buf, int index,
 		    ACPI_RESOURCE **resp);
 ACPI_STATUS	acpi_AppendBufferResource(ACPI_BUFFER *buf,
 		    ACPI_RESOURCE *res);
+UINT8		acpi_DSMQuery(ACPI_HANDLE h, uint8_t *uuid, int revision);
+ACPI_STATUS	acpi_EvaluateDSM(ACPI_HANDLE handle, uint8_t *uuid,
+		    int revision, uint64_t function, union acpi_object *package,
+		    ACPI_BUFFER *out_buf);
 ACPI_STATUS	acpi_EvaluateOSC(ACPI_HANDLE handle, uint8_t *uuid,
 		    int revision, int count, uint32_t *caps_in,
 		    uint32_t *caps_out, bool query);