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 > <heikki.krogerus@xxxxxxxxxxxxxxx> wrote: > > > > 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@xxxxxxxxxxxxxxx> > > --- > > 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