From 44b6b7661132b1b0e5fd3147ded66f1e4a817ca9 Mon Sep 17 00:00:00 2001 From: Mario Limonciello Date: Wed, 1 Nov 2017 14:25:35 -0500 Subject: platform/x86: wmi: create userspace interface for drivers For WMI operations that are only Set or Query readable and writable sysfs attributes created by WMI vendor drivers or the bus driver makes sense. For other WMI operations that are run on Method, there needs to be a way to guarantee to userspace that the results from the method call belong to the data request to the method call. Sysfs attributes don't work well in this scenario because two userspace processes may be competing at reading/writing an attribute and step on each other's data. When a WMI vendor driver declares a callback method in the wmi_driver the WMI bus driver will create a character device that maps to that function. This callback method will be responsible for filtering invalid requests and performing the actual call. That character device will correspond to this path: /dev/wmi/$driver Performing read() on this character device will provide the size of the buffer that the character device needs to perform calls. This buffer size can be set by vendor drivers through a new symbol or when MOF parsing is available by the MOF. Performing ioctl() on this character device will be interpretd by the WMI bus driver. It will perform sanity tests for size of data, test them for a valid instance, copy the data from userspace and pass iton to the vendor driver to further process and run. This creates an implicit policy that each driver will only be allowed a single character device. If a module matches multiple GUID's, the wmi_devices will need to be all handled by the same wmi_driver. The WMI vendor drivers will be responsible for managing inappropriate access to this character device and proper locking on data used by it. When a WMI vendor driver is unloaded the WMI bus driver will clean up the character device and any memory allocated for the call. Signed-off-by: Mario Limonciello Reviewed-by: Edward O'Callaghan Signed-off-by: Darren Hart (VMware) --- include/linux/wmi.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/wmi.h') diff --git a/include/linux/wmi.h b/include/linux/wmi.h index ddee427e0721..4757cb5077e5 100644 --- a/include/linux/wmi.h +++ b/include/linux/wmi.h @@ -18,6 +18,7 @@ #include #include +#include struct wmi_device { struct device dev; @@ -36,6 +37,8 @@ extern acpi_status wmidev_evaluate_method(struct wmi_device *wdev, extern union acpi_object *wmidev_block_query(struct wmi_device *wdev, u8 instance); +extern int set_required_buffer_size(struct wmi_device *wdev, u64 length); + struct wmi_device_id { const char *guid_string; }; @@ -47,6 +50,8 @@ struct wmi_driver { int (*probe)(struct wmi_device *wdev); int (*remove)(struct wmi_device *wdev); void (*notify)(struct wmi_device *device, union acpi_object *data); + long (*filter_callback)(struct wmi_device *wdev, unsigned int cmd, + struct wmi_ioctl_buffer *arg); }; extern int __must_check __wmi_driver_register(struct wmi_driver *driver, -- cgit v1.2.3