[PATCH v1 1/2] ACPI: utils: Add api to read _SUB from ACPI

Stefan Binding
2022-06-22T13:08:14Z

Add a wrapper function to read the _SUB string from ACPI.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
drivers/acpi/utils.c | 26 ++++++++++++++++++++++++++
include/linux/acpi.h | 8 ++++++++
2 files changed, 34 insertions(+)

diff --git a/drivers/acpi/utils.c b/drivers/acpi/utils.c
index 3a9773a09e19..5d1bdb79e372 100644
--- a/drivers/acpi/utils.c
+++ b/drivers/acpi/utils.c
@@ -291,6 +291,32 @@ int acpi_get_local_address(acpi_handle handle, u32 *addr)
}
EXPORT_SYMBOL(acpi_get_local_address);

+int acpi_get_sub(acpi_handle handle, char *sub, size_t size)
+{
+ struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+ union acpi_object *obj;
+ acpi_status status;
+ int ret;
+
+ status = acpi_evaluate_object(handle, METHOD_NAME__SUB, NULL, &buffer);
+ if (!ACPI_SUCCESS(status)) {
+ acpi_handle_debug(handle, "Reading ACPI _SUB failed: %#x\n", status);
+ return -ENOENT;
+ }
+
+ obj = buffer.pointer;
+ if (obj->type == ACPI_TYPE_STRING) {
+ ret = strscpy(sub, obj->string.pointer, size);
+ } else {
+ acpi_handle_warn(handle, "Warning ACPI _SUB did not return a string\n");
+ ret = -EINVAL;
+ }
+ acpi_os_free(buffer.pointer);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(acpi_get_sub);
+
acpi_status
acpi_evaluate_reference(acpi_handle handle,
acpi_string pathname,
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 4f82a5bc6d98..9bf18adf5920 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -21,6 +21,8 @@
#endif
#include <acpi/acpi.h>

+#define ACPI_MAX_SUB_BUF_SIZE 9
+
#ifdef CONFIG_ACPI

#include <linux/list.h>
@@ -762,6 +764,7 @@ static inline u64 acpi_arch_get_root_pointer(void)
#endif

int acpi_get_local_address(acpi_handle handle, u32 *addr);
+int acpi_get_sub(acpi_handle handle, char *sub, size_t size);

#else /* !CONFIG_ACPI */

@@ -1023,6 +1026,11 @@ static inline int acpi_get_local_address(acpi_handle handle, u32 *addr)
return -ENODEV;
}

+static int acpi_get_sub(acpi_handle handle, char *sub, size_t size)
+{
+ return -ENODEV;
+}
+
static inline int acpi_register_wakeup_handler(int wake_irq,
bool (*wakeup)(void *context), void *context)
{
--
2.25.1