Re: [PATCH v4 2/5] acpi: Store CRC-32 hash of the _PLD in struct acpi_device

Heikki Krogerus
2021-12-23T08:04:44Z

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@linux.intel.com> 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@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