platform/x86: dell-smbios-wmi: introduce userspace interface

It's important for the driver to provide a R/W ioctl to ensure that
two competing userspace processes don't race to provide or read each
others data.

This userspace character device will be used to perform SMBIOS calls
from any applications.

It provides an ioctl that will allow passing the WMI calling
interface buffer between userspace and kernel space.

This character device is intended to deprecate the dcdbas kernel module
and the interface that it provides to userspace.

To perform an SMBIOS IOCTL call using the character device userspace will
perform a read() on the the character device.  The WMI bus will provide
a u64 variable containing the necessary size of the IOCTL buffer.

The API for interacting with this interface is defined in documentation
as well as the WMI uapi header provides the format of the structures.

Not all userspace requests will be accepted.  The dell-smbios filtering
functionality will be used to prevent access to certain tokens and calls.

All whitelisted commands and tokens are now shared out to userspace so
applications don't need to define them in their own headers.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

1 files changed, 47 insertions, 0 deletions

diff --git a/include/uapi/linux/wmi.h b/include/uapi/linux/wmi.h
index 7e52350ac9b3..7a92e9e3d1c0 100644
--- a/include/uapi/linux/wmi.h
+++ b/include/uapi/linux/wmi.h
@@ -10,6 +10,7 @@
 #ifndef _UAPI_LINUX_WMI_H
 #define _UAPI_LINUX_WMI_H
 
+#include <linux/ioctl.h>
 #include <linux/types.h>
 
 /* WMI bus will filter all WMI vendor driver requests through this IOC */
@@ -23,4 +24,50 @@ struct wmi_ioctl_buffer {
 	__u8	data[];
 };
 
+/* This structure may be modified by the firmware when we enter
+ * system management mode through SMM, hence the volatiles
+ */
+struct calling_interface_buffer {
+	__u16 cmd_class;
+	__u16 cmd_select;
+	volatile __u32 input[4];
+	volatile __u32 output[4];
+} __packed;
+
+struct dell_wmi_extensions {
+	__u32 argattrib;
+	__u32 blength;
+	__u8 data[];
+} __packed;
+
+struct dell_wmi_smbios_buffer {
+	__u64 length;
+	struct calling_interface_buffer std;
+	struct dell_wmi_extensions	ext;
+} __packed;
+
+/* Whitelisted smbios class/select commands */
+#define CLASS_TOKEN_READ	0
+#define CLASS_TOKEN_WRITE	1
+#define SELECT_TOKEN_STD	0
+#define SELECT_TOKEN_BAT	1
+#define SELECT_TOKEN_AC		2
+#define CLASS_FLASH_INTERFACE	7
+#define SELECT_FLASH_INTERFACE	3
+#define CLASS_ADMIN_PROP	10
+#define SELECT_ADMIN_PROP	3
+#define CLASS_INFO		17
+#define SELECT_RFKILL		11
+#define SELECT_APP_REGISTRATION	3
+#define SELECT_DOCK		22
+
+/* whitelisted tokens */
+#define CAPSULE_EN_TOKEN	0x0461
+#define CAPSULE_DIS_TOKEN	0x0462
+#define WSMT_EN_TOKEN		0x04EC
+#define WSMT_DIS_TOKEN		0x04ED
+
+/* Dell SMBIOS calling IOCTL command used by dell-smbios-wmi */
+#define DELL_WMI_SMBIOS_CMD	_IOWR(WMI_IOC, 0, struct dell_wmi_smbios_buffer)
+
 #endif