[PATCH v11 6/9] ACPI: x86: s2idle: Add a function to get constraints for a device

[Mario Limonciello <mario.limonciello@amd.com>]

Other parts of the kernel may use constraints information to make
decisions on what power state to put a device into.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v9->v10:
 * split from other patches
 * kerneldoc fixes
 * move debug statement to this function
---
 drivers/acpi/x86/s2idle.c | 29 +++++++++++++++++++++++++++++
 include/linux/acpi.h      |  6 ++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/acpi/x86/s2idle.c b/drivers/acpi/x86/s2idle.c
index 0c8101acc92ef..2a1a482f4803a 100644
--- a/drivers/acpi/x86/s2idle.c
+++ b/drivers/acpi/x86/s2idle.c
@@ -295,6 +295,35 @@ static void lpi_device_get_constraints(void)
 	ACPI_FREE(out_obj);
 }
 
+/**
+ * acpi_get_lps0_constraint - get any LPS0 constraint for a device
+ * @dev: device to get constraints for
+ *
+ * Returns:
+ *  - If the constraint is enabled, the value for constraint.
+ *  - If the constraint is disabled, 0.
+ *  - Otherwise, -ENODEV.
+ */
+int acpi_get_lps0_constraint(struct device *dev)
+{
+	int i;
+
+	for (i = 0; i < lpi_constraints_table_size; ++i) {
+		static struct lpi_constraints *entry;
+		int val;
+
+		entry = &lpi_constraints_table[i];
+		if (!device_match_acpi_handle(dev, entry->handle))
+			continue;
+		val = entry->enabled ? entry->min_dstate : 0;
+		acpi_handle_debug(entry->handle,
+				  "ACPI device constraint: %d\n", val);
+		return val;
+	}
+
+	return -ENODEV;
+}
+
 static void lpi_check_constraints(void)
 {
 	int i;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 13a0fca3539f0..99458502a7510 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1109,6 +1109,12 @@ struct acpi_s2idle_dev_ops {
 };
 int acpi_register_lps0_dev(struct acpi_s2idle_dev_ops *arg);
 void acpi_unregister_lps0_dev(struct acpi_s2idle_dev_ops *arg);
+int acpi_get_lps0_constraint(struct device *dev);
+#else /* CONFIG_ACPI_SLEEP && CONFIG_X86 */
+static inline int acpi_get_lps0_constraint(struct device *dev)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_ACPI_SLEEP && CONFIG_X86 */
 #ifndef CONFIG_IA64
 void arch_reserve_mem_area(acpi_physical_address addr, size_t size);
-- 
2.34.1