linux-kernel - [PATCH v5 2/5] acpi: Store CRC-32 hash of the _PLD in struct acpi

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Date:   Thu, 23 Dec 2021 11:16:17 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Prashant Malani <pmalani@...omium.org>,
        linux-acpi@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 2/5] acpi: Store CRC-32 hash of the _PLD in struct acpi_device

Storing CRC-32 hash of the Physical Location of Device
object (_PLD) with devices that have it. The hash is stored
to a new struct acpi_device member "pld_crc".

The hash makes it easier to find devices that share a
location, as there is no need to evaluate the entire object
every time. Knowledge about devices that share a location
can be used in device drivers that need to know the
connections to other components inside a system. USB3 ports
will for example always share their location with a USB2
port.

Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
---
 drivers/acpi/scan.c     | 16 ++++++++++++++++
 include/acpi/acpi_bus.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 7ff55a197a583..113414c46b713 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -19,6 +19,7 @@
 #include <linux/dma-map-ops.h>
 #include <linux/platform_data/x86/apple.h>
 #include <linux/pgtable.h>
+#include <linux/crc32.h>
 
 #include "internal.h"
 
@@ -667,6 +668,19 @@ static int acpi_tie_acpi_dev(struct acpi_device *adev)
 	return 0;
 }
 
+static void acpi_store_pld_crc(struct acpi_device *adev)
+{
+	struct acpi_pld_info *pld;
+	acpi_status status;
+
+	status = acpi_get_physical_device_location(adev->handle, &pld);
+	if (ACPI_FAILURE(status))
+		return;
+
+	adev->pld_crc = crc32(~0, pld, sizeof(*pld));
+	ACPI_FREE(pld);
+}
+
 static int __acpi_device_add(struct acpi_device *device,
 			     void (*release)(struct device *))
 {
@@ -725,6 +739,8 @@ static int __acpi_device_add(struct acpi_device *device,
 	if (device->wakeup.flags.valid)
 		list_add_tail(&device->wakeup_list, &acpi_wakeup_device_list);
 
+	acpi_store_pld_crc(device);
+
 	mutex_unlock(&acpi_device_lock);
 
 	if (device->parent)
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 8e87ead2af341..f8c945418df23 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -360,6 +360,7 @@ struct acpi_gpio_mapping;
 
 /* Device */
 struct acpi_device {
+	u32 pld_crc;
 	int device_type;
 	acpi_handle handle;		/* no handle for fixed hardware */
 	struct fwnode_handle fwnode;
-- 
2.34.1