On Sat, Jan 16, 2016 at 5:11 AM, Michał Kępień [off-list ref] wrote:

quoted

My laptop has one RW data object, one RO data object, and one
totally inaccessible data object.  Check for the existence of the
accessor methods and report in sysfs.

The docs also permit WQxx getters for single-instance objects to
take no parameters.  Probe for that as well to avoid ACPICA warnings
about mismatched signatures.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/platform/x86/wmi.c | 94 ++++++++++++++++++++++++++++++++++++++++++++--
 include/linux/wmi.h        |  6 +++
 2 files changed, 96 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index 5571ae7354a1..49be61207c4a 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c

@@ -66,6 +66,8 @@ struct wmi_block {
      struct acpi_device *acpi_device;
      wmi_notify_handler handler;
      void *handler_data;
+
+     bool read_takes_no_args;        /* only defined if readable */
 };

@@ -216,6 +218,25 @@ static bool find_guid(const char *guid_string, struct wmi_block **out)
      return false;
 }

+static int get_subobj_info(acpi_handle handle, const char *pathname,
+                        struct acpi_device_info *info)
+{
+     acpi_handle subobj_handle;
+     acpi_status status;
+
+     status = acpi_get_handle(handle, (char *)pathname, &subobj_handle);
+     if (status == AE_NOT_FOUND)
+             return -ENOENT;
+     else if (ACPI_FAILURE(status))
+             return -EIO;
+
+     status = acpi_get_object_info(subobj_handle, &info);

acpi_get_object_info() allocates the returned buffer itself.  The latter
should then subsequently be freed by the caller.  One solution is to
change get_subobj_info() so that it takes a struct acpi_device_info **
as an argument, which should then be passed to acpi_get_object_info().
See also below.

I have an updated version of this patch in my queue.  I'll try to send
it early next week.

--Andy