[PATCH 1/2] acpi: utils: Add new acpi_dev_present helper

[Hans de Goede <hdegoede@redhat.com>]

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.

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>
---
 drivers/acpi/utils.c    | 34 ++++++++++++++++++++++++++++++++++
 include/acpi/acpi_bus.h |  1 +
 include/linux/acpi.h    |  5 +++++
 3 files changed, 40 insertions(+)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 22c0995..40f8953 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -736,6 +736,40 @@ bool acpi_dev_found(const char *hid)
 }
 EXPORT_SYMBOL(acpi_dev_found);
 
+static acpi_status acpi_dev_present_cb(acpi_handle ah, u32 level, void *ctx,
+				     void **retval)
+{
+	/*
+	 * acpi_get_devices() does all the work for us, if we get called
+	 * a device with a matching hid has been found and its _STA indicates
+	 * it is present.
+	 */
+	*(bool *)ctx = true;
+	return AE_CTRL_TERMINATE;
+}
+
+/**
+ * acpi_dev_present - Detect that a given ACPI device is present
+ * @hid: Hardware ID of the device.
+ *
+ * Return %true if the 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.
+ */
+bool acpi_dev_present(const char *hid)
+{
+	bool present = false;
+
+	acpi_get_devices(hid, acpi_dev_present_cb, &present, NULL);
+
+	return present;
+}
+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.
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index ef0ae8a..29f6b5f 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -88,6 +88,7 @@ acpi_evaluate_dsm_typed(acpi_handle handle, const u8 *uuid, u64 rev, u64 func,
 	}
 
 bool acpi_dev_found(const char *hid);
+bool acpi_dev_present(const char *hid);
 
 #ifdef CONFIG_ACPI
 
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 673acda..059ffdc 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -614,6 +614,11 @@ static inline bool acpi_dev_found(const char *hid)
 	return false;
 }
 
+static inline bool acpi_dev_present(const char *hid)
+{
+	return false;
+}
+
 static inline bool is_acpi_node(struct fwnode_handle *fwnode)
 {
 	return false;
-- 
2.9.3