platform/x86: ISST: Add common API to register and handle ioctls

Encapsulate common functions which all Intel Speed Select Technology
interface drivers can use. This creates API to register misc device for
user kernel communication and handle all common IOCTLs. As part of the
registry it allows a callback which is to handle domain specific ioctl
processing.

There can be multiple drivers register for services, which can be built
as modules. So this driver handle contention during registry and as well
as during removal. Once user space opened the misc device, the registered
driver will be prevented from removal. Also once misc device is opened by
the user space new client driver can't register, till the misc device is
closed.

There are two types of client drivers, one to handle mail box interface
and the other is to allow direct read/write to some specific MMIO space.

This common driver implements IOCTL ISST_IF_GET_PLATFORM_INFO.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/drivers/platform/x86/intel_speed_select_if/isst_if_common.h b/drivers/platform/x86/intel_speed_select_if/isst_if_common.h
new file mode 100644
index 000000000000..11f339226fb4
--- /dev/null
+++ b/drivers/platform/x86/intel_speed_select_if/isst_if_common.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Intel Speed Select Interface: Drivers Internal defines
+ * Copyright (c) 2019, Intel Corporation.
+ * All rights reserved.
+ *
+ * Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
+ */
+
+#ifndef __ISST_IF_COMMON_H
+#define __ISST_IF_COMMON_H
+
+/*
+ * Validate maximum commands in a single request.
+ * This is enough to handle command to every core in one ioctl, or all
+ * possible message id to one CPU. Limit is also helpful for resonse time
+ * per IOCTL request, as PUNIT may take different times to process each
+ * request and may hold for long for too many commands.
+ */
+#define ISST_IF_CMD_LIMIT	64
+
+#define ISST_IF_API_VERSION	0x01
+#define ISST_IF_DRIVER_VERSION	0x01
+
+#define ISST_IF_DEV_MBOX	0
+#define ISST_IF_DEV_MMIO	1
+#define ISST_IF_DEV_MAX		2
+
+/**
+ * struct isst_if_cmd_cb - Used to register a IOCTL handler
+ * @registered:	Used by the common code to store registry. Caller don't
+ *		to touch this field
+ * @cmd_size:	The command size of the individual command in IOCTL
+ * @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
+ * @cmd_callback: Callback function to handle IOCTL. The callback has the
+ *		command pointer with data for command. There is a pointer
+ *		called write_only, which when set, will not copy the
+ *		response to user ioctl buffer. The "resume" argument
+ *		can be used to avoid storing the command for replay
+ *		during system resume
+ *
+ * This structure is used to register an handler for IOCTL. To avoid
+ * code duplication common code handles all the IOCTL command read/write
+ * including handling multiple command in single IOCTL. The caller just
+ * need to execute a command via the registered callback.
+ */
+struct isst_if_cmd_cb {
+	int registered;
+	int cmd_size;
+	int offset;
+	struct module *owner;
+	long (*cmd_callback)(u8 *ptr, int *write_only, int resume);
+};
+
+/* Internal interface functions */
+int isst_if_cdev_register(int type, struct isst_if_cmd_cb *cb);
+void isst_if_cdev_unregister(int type);
+#endif