Re: [PATCH RFC v3 01/21] ACPI: Only enumerate enabled (or functional) devices

Rafael J. Wysocki
2023-12-15T19:47:34Z

On Friday, December 15, 2023 5:15:39 PM CET Jonathan Cameron wrote:
> On Fri, 15 Dec 2023 15:31:55 +0000
> "Russell King (Oracle)" <linux@armlinux.org.uk> wrote:
>
> > On Thu, Dec 14, 2023 at 07:37:10PM +0100, Rafael J. Wysocki wrote:
> > > On Thu, Dec 14, 2023 at 7:16 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
> > > >
> > > > On Thu, Dec 14, 2023 at 7:10 PM Russell King (Oracle)
> > > > <linux@armlinux.org.uk> wrote:
> > > > > I guess we need something like:
> > > > >
> > > > > if (device->status.present)
> > > > > return device->device_type != ACPI_BUS_TYPE_PROCESSOR ||
> > > > > device->status.enabled;
> > > > > else
> > > > > return device->status.functional;
> > > > >
> > > > > so we only check device->status.enabled for processor-type devices?
> > > >
> > > > Yes, something like this.
> > >
> > > However, that is not sufficient, because there are
> > > ACPI_BUS_TYPE_DEVICE devices representing processors.
> > >
> > > I'm not sure about a clean way to do it ATM.
> >
> > Ok, how about:
> >
> > static bool acpi_dev_is_processor(const struct acpi_device *device)
> > {
> > struct acpi_hardware_id *hwid;
> >
> > if (device->device_type == ACPI_BUS_TYPE_PROCESSOR)
> > return true;
> >
> > if (device->device_type != ACPI_BUS_TYPE_DEVICE)
> > return false;
> >
> > list_for_each_entry(hwid, &device->pnp.ids, list)
> > if (!strcmp(ACPI_PROCESSOR_OBJECT_HID, hwid->id) ||
> > !strcmp(ACPI_PROCESSOR_DEVICE_HID, hwid->id))
> > return true;
> >
> > return false;
> > }
> >
> > and then:
> >
> > if (device->status.present)
> > return !acpi_dev_is_processor(device) || device->status.enabled;
> > else
> > return device->status.functional;
> >
> > ?
> >
> Changing it to CPU only for now makes sense to me and I think this code snippet should do the
> job. Nice and simple.

Well, except that it does checks that are done elsewhere slightly
differently, which from the maintenance POV is not nice.

Maybe something like the appended patch (untested).

---
drivers/acpi/acpi_processor.c | 11 +++++++++++
drivers/acpi/internal.h | 3 +++
drivers/acpi/scan.c | 24 +++++++++++++++++++++++-
3 files changed, 37 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/acpi_processor.c
===================================================================
--- linux-pm.orig/drivers/acpi/acpi_processor.c
+++ linux-pm/drivers/acpi/acpi_processor.c
@@ -644,6 +644,17 @@ static struct acpi_scan_handler processo
},
};

+bool acpi_device_is_processor(const struct acpi_device *adev)
+{
+ if (adev->device_type == ACPI_BUS_TYPE_PROCESSOR)
+ return true;
+
+ if (adev->device_type != ACPI_BUS_TYPE_DEVICE)
+ return false;
+
+ return acpi_scan_check_handler(adev, &processor_handler);
+}
+
static int acpi_processor_container_attach(struct acpi_device *dev,
const struct acpi_device_id *id)
{
Index: linux-pm/drivers/acpi/internal.h
===================================================================
--- linux-pm.orig/drivers/acpi/internal.h
+++ linux-pm/drivers/acpi/internal.h
@@ -62,6 +62,8 @@ void acpi_sysfs_add_hotplug_profile(stru
int acpi_scan_add_handler_with_hotplug(struct acpi_scan_handler *handler,
const char *hotplug_profile_name);
void acpi_scan_hotplug_enabled(struct acpi_hotplug_profile *hotplug, bool val);
+bool acpi_scan_check_handler(const struct acpi_device *adev,
+ struct acpi_scan_handler *handler);

#ifdef CONFIG_DEBUG_FS
extern struct dentry *acpi_debugfs_dir;
@@ -133,6 +135,7 @@ int acpi_bus_register_early_device(int t
const struct acpi_device *acpi_companion_match(const struct device *dev);
int __acpi_device_uevent_modalias(const struct acpi_device *adev,
struct kobj_uevent_env *env);
+bool acpi_device_is_processor(const struct acpi_device *adev);

/* --------------------------------------------------------------------------
Power Resource
Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1938,6 +1938,19 @@ static bool acpi_scan_handler_matching(s
return false;
}

+bool acpi_scan_check_handler(const struct acpi_device *adev,
+ struct acpi_scan_handler *handler)
+{
+ struct acpi_hardware_id *hwid;
+
+ list_for_each_entry(hwid, &adev->pnp.ids, list) {
+ if (acpi_scan_handler_matching(handler, hwid->id, NULL))
+ return true;
+ }
+
+ return false;
+}
+
static struct acpi_scan_handler *acpi_scan_match_handler(const char *idstr,
const struct acpi_device_id **matchid)
{
@@ -2410,7 +2423,16 @@ bool acpi_dev_ready_for_enumeration(cons
if (device->flags.honor_deps && device->dep_unmet)
return false;

- return acpi_device_is_present(device);
+ if (device->status.functional)
+ return true;
+
+ if (!device->status.present)
+ return false;
+
+ if (device->status.enabled)
+ return true; /* Fast path. */
+
+ return !acpi_device_is_processor(device);
}
EXPORT_SYMBOL_GPL(acpi_dev_ready_for_enumeration);