On Wed, Dec 22, 2021 at 05:55:32PM +0100, Rafael J. Wysocki wrote:

On Wed, Dec 22, 2021 at 3:33 PM Heikki Krogerus
[off-list ref] wrote:

quoted

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@linux.intel.com>
---
 drivers/acpi/scan.c     | 16 ++++++++++++++++
 include/acpi/acpi_bus.h | 14 +++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

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..1977db19458ed 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h

@@ -356,10 +356,23 @@ struct acpi_device_data {
        struct list_head subnodes;
 };

+/*
+ * struct acpi_device_location - Device location based on _PLD
+ * @devices: List of devices that share this location
+ * @node: Entry in the internal list of locations
+ * @pld_crc: CRC-32 hash of the _PLD
+ */
+struct acpi_device_location {
+       struct list_head devices;
+       struct list_head node;
+       u32 pld_crc;
+};

Does this get used anywhere or is it a leftover from the previous version?

No. I'm sorry that was supposed to be removed. I'll resend.

thanks,

-- 
heikki