platform/x86: ISST: Add API version of the target

User space can get the API version using IOCTL
ISST_IF_GET_PLATFORM_INFO. This information can be used to get IOCTLs
supported by the kernel driver. This version is hardcoded in the driver.

Allow the registered client to specify the supported API version. In
this way a registered client can specify a higher API version to extend
IOCTL set.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Link: https://lore.kernel.org/r/20230211063257.311746-5-srinivas.pandruvada@linux.intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/intel/speed_select_if/isst_if_common.c

@@ -262,11 +262,13 @@ bool isst_if_mbox_cmd_set_req(struct isst_if_mbox_cmd *cmd)
 }
 EXPORT_SYMBOL_GPL(isst_if_mbox_cmd_set_req);
 
+static int isst_if_api_version;
+
 static int isst_if_get_platform_info(void __user *argp)
 {
 	struct isst_if_platform_info info;
 
-	info.api_version = ISST_IF_API_VERSION;
+	info.api_version = isst_if_api_version;
 	info.driver_version = ISST_IF_DRIVER_VERSION;
 	info.max_cmds_per_ioctl = ISST_IF_CMD_LIMIT;
 	info.mbox_supported = punit_callbacks[ISST_IF_DEV_MBOX].registered;
@@ -767,6 +769,10 @@ int isst_if_cdev_register(int device_type, struct isst_if_cmd_cb *cb)
 		mutex_unlock(&punit_misc_dev_open_lock);
 		return -EAGAIN;
 	}
+	if (!cb->api_version)
+		cb->api_version = ISST_IF_API_VERSION;
+	if (cb->api_version > isst_if_api_version)
+		isst_if_api_version = cb->api_version;
 	memcpy(&punit_callbacks[device_type], cb, sizeof(*cb));
 	punit_callbacks[device_type].registered = 1;
 	mutex_unlock(&punit_misc_dev_open_lock);

drivers/platform/x86/intel/speed_select_if/isst_if_common.h

@@ -41,6 +41,7 @@
  * @offset:	Offset to the first valid member in command structure.
  *		This will be the offset of the start of the command
  *		after command count field
+ * @api_version: API version supported for this target. 0, if none.
  * @owner:	Registered module owner
  * @cmd_callback: Callback function to handle IOCTL. The callback has the
  *		command pointer with data for command. There is a pointer
@@ -60,7 +61,7 @@ struct isst_if_cmd_cb {
 	int registered;
 	int cmd_size;
 	int offset;
-
+	int api_version;
 	struct module *owner;
 	long (*cmd_callback)(u8 *ptr, int *write_only, int resume);
 	long (*def_ioctl)(struct file *file, unsigned int cmd, unsigned long arg);