ACPI / utils: Add new acpi_dev_present helper

acpi_dev_found just iterates over all ACPI-ids and sees if one matches.
This means that it will return true for devices which are in the DSDT
but disabled (their _STA method returns 0).

For some drivers it is useful to be able to check if a certain HID
is not only present in the namespace, but also actually present as in
acpi_device_is_present() will return true for the device. For example
because if a certain device is present then the driver will want to use
an extcon or IIO ADC channel provided by that device.

This commit adds a new acpi_dev_present helper which drivers can use
to this end.

Like acpi_dev_found, acpi_dev_present take a HID as argument, but
it also has 2 extra optional arguments to only check for an ACPI
device with a specific UID and/or HRV value. This makes it more
generic and allows it to replace custom code doing similar checks
in several places.

Arguably acpi_dev_present is what acpi_dev_found should have been, but
there are too many users to just change acpi_dev_found without the risk
of breaking something.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 22c09952e177..27d0dcfcf47d 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -736,6 +736,72 @@ bool acpi_dev_found(const char *hid)
 }
 EXPORT_SYMBOL(acpi_dev_found);
 
+struct acpi_dev_present_info {
+        struct acpi_device_id hid[2];
+        const char *uid;
+        s64 hrv;
+};
+
+static int acpi_dev_present_cb(struct device *dev, void *data)
+{
+        struct acpi_device *adev = to_acpi_device(dev);
+        struct acpi_dev_present_info *match = data;
+        unsigned long long hrv;
+        acpi_status status;
+
+        if (acpi_match_device_ids(adev, match->hid))
+                return 0;
+
+        if (match->uid && (!adev->pnp.unique_id ||
+            strcmp(adev->pnp.unique_id, match->uid)))
+                return 0;
+
+        if (match->hrv == -1)
+                return 1;
+
+        status = acpi_evaluate_integer(adev->handle, "_HRV", NULL, &hrv);
+        if (ACPI_FAILURE(status))
+                return 0;
+
+        return hrv == match->hrv;
+}
+
+/**
+ * acpi_dev_present - Detect that a given ACPI device is present
+ * @hid: Hardware ID of the device.
+ * @uid: Unique ID of the device, pass NULL to not check _UID
+ * @hrv: Hardware Revision of the device, pass -1 to not check _HRV
+ *
+ * Return %true if a matching device was present at the moment of invocation.
+ * Note that if the device is pluggable, it may since have disappeared.
+ *
+ * Note that unlike acpi_dev_found() this function checks the status
+ * of the device. So for devices which are present in the dsdt, but
+ * which are disabled (their _STA callback returns 0) this function
+ * will return false.
+ *
+ * For this function to work, acpi_bus_scan() must have been executed
+ * which happens in the subsys_initcall() subsection. Hence, do not
+ * call from a subsys_initcall() or earlier (use acpi_get_devices()
+ * instead). Calling from module_init() is fine (which is synonymous
+ * with device_initcall()).
+ */
+bool acpi_dev_present(const char *hid, const char *uid, s64 hrv)
+{
+        struct acpi_dev_present_info match = {};
+        struct device *dev;
+
+        strlcpy(match.hid[0].id, hid, sizeof(match.hid[0].id));
+        match.uid = uid;
+        match.hrv = hrv;
+
+        dev = bus_find_device(&acpi_bus_type, NULL, &match,
+                              acpi_dev_present_cb);
+
+        return !!dev;
+}
+EXPORT_SYMBOL(acpi_dev_present);
+
 /*
  * acpi_backlight= handling, this is done here rather then in video_detect.c
  * because __setup cannot be used in modules.