From b625fe694626992c1d640b37c691cfcfc58d6006 Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: Tue, 1 Mar 2022 00:39:30 +0200
Subject: [PATCH] ACPI: docs: enumeration: Discourage to use custom _DSM methods
Git-commit: b625fe694626992c1d640b37c691cfcfc58d6006
Patch-mainline: v5.18-rc1
References: git-fixes

Since we have _DSD established and specified (ACPI v5.1+) there is no
need to use custom _DSM methods. Rewrite documentation to use _DSD.

Fixes: f60e7074902a ("misc: at25: Make use of device property API")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 .../firmware-guide/acpi/enumeration.rst       | 48 ++++++++-----------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 74b830b2fd59..cda41e4255eb 100644
--- a/Documentation/firmware-guide/acpi/enumeration.rst
+++ b/Documentation/firmware-guide/acpi/enumeration.rst
@@ -188,43 +188,37 @@ to at25 SPI eeprom driver (this is meant for the above ACPI snippet)::
 	};
 
 Note that this driver actually needs more information like page size of the
-eeprom etc. but at the time writing this there is no standard way of
-passing those. One idea is to return this in _DSM method like::
+eeprom, etc. This information can be passed via _DSD method like::
 
 	Device (EEP0)
 	{
 		...
-		Method (_DSM, 4, NotSerialized)
+		Name (_DSD, Package ()
 		{
-			Store (Package (6)
+			ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
+			Package ()
 			{
-				"byte-len", 1024,
-				"addr-mode", 2,
-				"page-size, 32
-			}, Local0)
-
-			// Check UUIDs etc.
-
-			Return (Local0)
-		}
-
-Then the at25 SPI driver can get this configuration by calling _DSM on its
-ACPI handle like::
-
-	struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
-	struct acpi_object_list input;
-	acpi_status status;
+				Package () { "size", 1024 },
+				Package () { "pagesize", 32 },
+				Package () { "address-width", 16 },
+			}
+		})
+	}
 
-	/* Fill in the input buffer */
+Then the at25 SPI driver can get this configuration by calling device property
+APIs during ->probe() phase like::
 
-	status = acpi_evaluate_object(ACPI_HANDLE(&spi->dev), "_DSM",
-				      &input, &output);
-	if (ACPI_FAILURE(status))
-		/* Handle the error */
+	err = device_property_read_u32(dev, "size", &size);
+	if (err)
+		...error handling...
 
-	/* Extract the data here */
+	err = device_property_read_u32(dev, "pagesize", &page_size);
+	if (err)
+		...error handling...
 
-	kfree(output.pointer);
+	err = device_property_read_u32(dev, "address-width", &addr_width);
+	if (err)
+		...error handling...
 
 I2C serial bus support
 ======================
-- 
2.31.1