[linux-2.6-block.git] / drivers / platform / chrome / wilco_ec / telemetry.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Telemetry communication for Wilco EC
 *
 * Copyright 2019 Google LLC
 *
 * The Wilco Embedded Controller is able to send telemetry data
 * which is useful for enterprise applications. A daemon running on
 * the OS sends a command to the EC via a write() to a char device,
 * and can read the response with a read(). The write() request is
 * verified by the driver to ensure that it is performing only one
 * of the allowlisted commands, and that no extraneous data is
 * being transmitted to the EC. The response is passed directly
 * back to the reader with no modification.
 *
 * The character device will appear as /dev/wilco_telemN, where N
 * is some small non-negative integer, starting with 0. Only one
 * process may have the file descriptor open at a time. The calling
 * userspace program needs to keep the device file descriptor open
 * between the calls to write() and read() in order to preserve the
 * response. Up to 32 bytes will be available for reading.
 *
 * For testing purposes, try requesting the EC's firmware build
 * date, by sending the WILCO_EC_TELEM_GET_VERSION command with
 * argument index=3. i.e. write [0x38, 0x00, 0x03]
 * to the device node. An ASCII string of the build date is
 * returned.
 */

#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>

#define TELEM_DEV_NAME		"wilco_telem"
#define TELEM_CLASS_NAME	TELEM_DEV_NAME
#define DRV_NAME		TELEM_DEV_NAME
#define TELEM_DEV_NAME_FMT	(TELEM_DEV_NAME "%d")
static struct class telem_class = {
	.owner	= THIS_MODULE,
	.name	= TELEM_CLASS_NAME,
};

/* Keep track of all the device numbers used. */
#define TELEM_MAX_DEV 128
static int telem_major;
static DEFINE_IDA(telem_ida);

/* EC telemetry command codes */
#define WILCO_EC_TELEM_GET_LOG			0x99
#define WILCO_EC_TELEM_GET_VERSION		0x38
#define WILCO_EC_TELEM_GET_FAN_INFO		0x2E
#define WILCO_EC_TELEM_GET_DIAG_INFO		0xFA
#define WILCO_EC_TELEM_GET_TEMP_INFO		0x95
#define WILCO_EC_TELEM_GET_TEMP_READ		0x2C
#define WILCO_EC_TELEM_GET_BATT_EXT_INFO	0x07
#define WILCO_EC_TELEM_GET_BATT_PPID_INFO	0x8A

#define TELEM_ARGS_SIZE_MAX	30

/*
 * The following telem_args_get_* structs are embedded within the |args| field
 * of wilco_ec_telem_request.
 */

struct telem_args_get_log {
	u8 log_type;
	u8 log_index;
} __packed;

/*
 * Get a piece of info about the EC firmware version:
 * 0 = label
 * 1 = svn_rev
 * 2 = model_no
 * 3 = build_date
 * 4 = frio_version
 */
struct telem_args_get_version {
	u8 index;
} __packed;

struct telem_args_get_fan_info {
	u8 command;
	u8 fan_number;
	u8 arg;
} __packed;

struct telem_args_get_diag_info {
	u8 type;
	u8 sub_type;
} __packed;

struct telem_args_get_temp_info {
	u8 command;
	u8 index;
	u8 field;
	u8 zone;
} __packed;

struct telem_args_get_temp_read {
	u8 sensor_index;
} __packed;

struct telem_args_get_batt_ext_info {
	u8 var_args[5];
} __packed;

struct telem_args_get_batt_ppid_info {
	u8 always1; /* Should always be 1 */
} __packed;

/**
 * struct wilco_ec_telem_request - Telemetry command and arguments sent to EC.
 * @command: One of WILCO_EC_TELEM_GET_* command codes.
 * @reserved: Must be 0.
 * @args: The first N bytes are one of telem_args_get_* structs, the rest is 0.
 */
struct wilco_ec_telem_request {
	u8 command;
	u8 reserved;
	union {
		u8 buf[TELEM_ARGS_SIZE_MAX];
		struct telem_args_get_log		get_log;
		struct telem_args_get_version		get_version;
		struct telem_args_get_fan_info		get_fan_info;
		struct telem_args_get_diag_info		get_diag_info;
		struct telem_args_get_temp_info		get_temp_info;
		struct telem_args_get_temp_read		get_temp_read;
		struct telem_args_get_batt_ext_info	get_batt_ext_info;
		struct telem_args_get_batt_ppid_info	get_batt_ppid_info;
	} args;
} __packed;

/**
 * check_telem_request() - Ensure that a request from userspace is valid.
 * @rq: Request buffer copied from userspace.
 * @size: Number of bytes copied from userspace.
 *
 * Return: 0 if valid, -EINVAL if bad command or reserved byte is non-zero,
 *         -EMSGSIZE if the request is too long.
 *
 * We do not want to allow userspace to send arbitrary telemetry commands to
 * the EC. Therefore we check to ensure that
 * 1. The request follows the format of struct wilco_ec_telem_request.
 * 2. The supplied command code is one of the allowlisted commands.
 * 3. The request only contains the necessary data for the header and arguments.
 */
static int check_telem_request(struct wilco_ec_telem_request *rq,
			       size_t size)
{
	size_t max_size = offsetof(struct wilco_ec_telem_request, args);

	if (rq->reserved)
		return -EINVAL;

	switch (rq->command) {
	case WILCO_EC_TELEM_GET_LOG:
		max_size += sizeof(rq->args.get_log);
		break;
	case WILCO_EC_TELEM_GET_VERSION:
		max_size += sizeof(rq->args.get_version);
		break;
	case WILCO_EC_TELEM_GET_FAN_INFO:
		max_size += sizeof(rq->args.get_fan_info);
		break;
	case WILCO_EC_TELEM_GET_DIAG_INFO:
		max_size += sizeof(rq->args.get_diag_info);
		break;
	case WILCO_EC_TELEM_GET_TEMP_INFO:
		max_size += sizeof(rq->args.get_temp_info);
		break;
	case WILCO_EC_TELEM_GET_TEMP_READ:
		max_size += sizeof(rq->args.get_temp_read);
		break;
	case WILCO_EC_TELEM_GET_BATT_EXT_INFO:
		max_size += sizeof(rq->args.get_batt_ext_info);
		break;
	case WILCO_EC_TELEM_GET_BATT_PPID_INFO:
		if (rq->args.get_batt_ppid_info.always1 != 1)
			return -EINVAL;

		max_size += sizeof(rq->args.get_batt_ppid_info);
		break;
	default:
		return -EINVAL;
	}

	return (size <= max_size) ? 0 : -EMSGSIZE;
}

/**
 * struct telem_device_data - Data for a Wilco EC device that queries telemetry.
 * @cdev: Char dev that userspace reads and polls from.
 * @dev: Device associated with the %cdev.
 * @ec: Wilco EC that we will be communicating with using the mailbox interface.
 * @available: Boolean of if the device can be opened.
 */
struct telem_device_data {
	struct device dev;
	struct cdev cdev;
	struct wilco_ec_device *ec;
	atomic_t available;
};

#define TELEM_RESPONSE_SIZE	EC_MAILBOX_DATA_SIZE

/**
 * struct telem_session_data - Data that exists between open() and release().
 * @dev_data: Pointer to get back to the device data and EC.
 * @request: Command and arguments sent to EC.
 * @response: Response buffer of data from EC.
 * @has_msg: Is there data available to read from a previous write?
 */
struct telem_session_data {
	struct telem_device_data *dev_data;
	struct wilco_ec_telem_request request;
	u8 response[TELEM_RESPONSE_SIZE];
	bool has_msg;
};

/**
 * telem_open() - Callback for when the device node is opened.
 * @inode: inode for this char device node.
 * @filp: file for this char device node.
 *
 * We need to ensure that after writing a command to the device,
 * the same userspace process reads the corresponding result.
 * Therefore, we increment a refcount on opening the device, so that
 * only one process can communicate with the EC at a time.
 *
 * Return: 0 on success, or negative error code on failure.
 */
static int telem_open(struct inode *inode, struct file *filp)
{
	struct telem_device_data *dev_data;
	struct telem_session_data *sess_data;

	/* Ensure device isn't already open */
	dev_data = container_of(inode->i_cdev, struct telem_device_data, cdev);
	if (atomic_cmpxchg(&dev_data->available, 1, 0) == 0)
		return -EBUSY;

	get_device(&dev_data->dev);

	sess_data = kzalloc(sizeof(*sess_data), GFP_KERNEL);
	if (!sess_data) {
		atomic_set(&dev_data->available, 1);
		return -ENOMEM;
	}
	sess_data->dev_data = dev_data;
	sess_data->has_msg = false;

	stream_open(inode, filp);
	filp->private_data = sess_data;

	return 0;
}

static ssize_t telem_write(struct file *filp, const char __user *buf,
			   size_t count, loff_t *pos)
{
	struct telem_session_data *sess_data = filp->private_data;
	struct wilco_ec_message msg = {};
	int ret;

	if (count > sizeof(sess_data->request))
		return -EMSGSIZE;
	memset(&sess_data->request, 0, sizeof(sess_data->request));
	if (copy_from_user(&sess_data->request, buf, count))
		return -EFAULT;
	ret = check_telem_request(&sess_data->request, count);
	if (ret < 0)
		return ret;

	memset(sess_data->response, 0, sizeof(sess_data->response));
	msg.type = WILCO_EC_MSG_TELEMETRY;
	msg.request_data = &sess_data->request;
	msg.request_size = sizeof(sess_data->request);
	msg.response_data = sess_data->response;
	msg.response_size = sizeof(sess_data->response);

	ret = wilco_ec_mailbox(sess_data->dev_data->ec, &msg);
	if (ret < 0)
		return ret;
	if (ret != sizeof(sess_data->response))
		return -EMSGSIZE;

	sess_data->has_msg = true;

	return count;
}

static ssize_t telem_read(struct file *filp, char __user *buf, size_t count,
			  loff_t *pos)
{
	struct telem_session_data *sess_data = filp->private_data;

	if (!sess_data->has_msg)
		return -ENODATA;
	if (count > sizeof(sess_data->response))
		return -EINVAL;

	if (copy_to_user(buf, sess_data->response, count))
		return -EFAULT;

	sess_data->has_msg = false;

	return count;
}

static int telem_release(struct inode *inode, struct file *filp)
{
	struct telem_session_data *sess_data = filp->private_data;

	atomic_set(&sess_data->dev_data->available, 1);
	put_device(&sess_data->dev_data->dev);
	kfree(sess_data);

	return 0;
}

static const struct file_operations telem_fops = {
	.open = telem_open,
	.write = telem_write,
	.read = telem_read,
	.release = telem_release,
	.llseek = no_llseek,
	.owner = THIS_MODULE,
};

/**
 * telem_device_free() - Callback to free the telem_device_data structure.
 * @d: The device embedded in our device data, which we have been ref counting.
 *
 * Once all open file descriptors are closed and the device has been removed,
 * the refcount of the device will fall to 0 and this will be called.
 */
static void telem_device_free(struct device *d)
{
	struct telem_device_data *dev_data;

	dev_data = container_of(d, struct telem_device_data, dev);
	kfree(dev_data);
}

/**
 * telem_device_probe() - Callback when creating a new device.
 * @pdev: platform device that we will be receiving telems from.
 *
 * This finds a free minor number for the device, allocates and initializes
 * some device data, and creates a new device and char dev node.
 *
 * Return: 0 on success, negative error code on failure.
 */
static int telem_device_probe(struct platform_device *pdev)
{
	struct telem_device_data *dev_data;
	int error, minor;

	/* Get the next available device number */
	minor = ida_alloc_max(&telem_ida, TELEM_MAX_DEV-1, GFP_KERNEL);
	if (minor < 0) {
		error = minor;
		dev_err(&pdev->dev, "Failed to find minor number: %d\n", error);
		return error;
	}

	dev_data = kzalloc(sizeof(*dev_data), GFP_KERNEL);
	if (!dev_data) {
		ida_simple_remove(&telem_ida, minor);
		return -ENOMEM;
	}

	/* Initialize the device data */
	dev_data->ec = dev_get_platdata(&pdev->dev);
	atomic_set(&dev_data->available, 1);
	platform_set_drvdata(pdev, dev_data);

	/* Initialize the device */
	dev_data->dev.devt = MKDEV(telem_major, minor);
	dev_data->dev.class = &telem_class;
	dev_data->dev.release = telem_device_free;
	dev_set_name(&dev_data->dev, TELEM_DEV_NAME_FMT, minor);
	device_initialize(&dev_data->dev);

	/* Initialize the character device and add it to userspace */;
	cdev_init(&dev_data->cdev, &telem_fops);
	error = cdev_device_add(&dev_data->cdev, &dev_data->dev);
	if (error) {
		put_device(&dev_data->dev);
		ida_simple_remove(&telem_ida, minor);
		return error;
	}

	return 0;
}

static int telem_device_remove(struct platform_device *pdev)
{
	struct telem_device_data *dev_data = platform_get_drvdata(pdev);

	cdev_device_del(&dev_data->cdev, &dev_data->dev);
	ida_simple_remove(&telem_ida, MINOR(dev_data->dev.devt));
	put_device(&dev_data->dev);

	return 0;
}

static struct platform_driver telem_driver = {
	.probe = telem_device_probe,
	.remove = telem_device_remove,
	.driver = {
		.name = DRV_NAME,
	},
};

static int __init telem_module_init(void)
{
	dev_t dev_num = 0;
	int ret;

	ret = class_register(&telem_class);
	if (ret) {
		pr_err(DRV_NAME ": Failed registering class: %d\n", ret);
		return ret;
	}

	/* Request the kernel for device numbers, starting with minor=0 */
	ret = alloc_chrdev_region(&dev_num, 0, TELEM_MAX_DEV, TELEM_DEV_NAME);
	if (ret) {
		pr_err(DRV_NAME ": Failed allocating dev numbers: %d\n", ret);
		goto destroy_class;
	}
	telem_major = MAJOR(dev_num);

	ret = platform_driver_register(&telem_driver);
	if (ret < 0) {
		pr_err(DRV_NAME ": Failed registering driver: %d\n", ret);
		goto unregister_region;
	}

	return 0;

unregister_region:
	unregister_chrdev_region(MKDEV(telem_major, 0), TELEM_MAX_DEV);
destroy_class:
	class_unregister(&telem_class);
	ida_destroy(&telem_ida);
	return ret;
}

static void __exit telem_module_exit(void)
{
	platform_driver_unregister(&telem_driver);
	unregister_chrdev_region(MKDEV(telem_major, 0), TELEM_MAX_DEV);
	class_unregister(&telem_class);
	ida_destroy(&telem_ida);
}

module_init(telem_module_init);
module_exit(telem_module_exit);

MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
MODULE_DESCRIPTION("Wilco EC telemetry driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:" DRV_NAME);
Commit	Line	Data
1210d1e6 NC	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Telemetry communication for Wilco EC
	4	*
	5	* Copyright 2019 Google LLC
	6	*
	7	* The Wilco Embedded Controller is able to send telemetry data
	8	* which is useful for enterprise applications. A daemon running on
	9	* the OS sends a command to the EC via a write() to a char device,
	10	* and can read the response with a read(). The write() request is
	11	* verified by the driver to ensure that it is performing only one
3b81d8bd	12	* of the allowlisted commands, and that no extraneous data is
1210d1e6 NC	13	* being transmitted to the EC. The response is passed directly
	14	* back to the reader with no modification.
	15	*
	16	* The character device will appear as /dev/wilco_telemN, where N
	17	* is some small non-negative integer, starting with 0. Only one
	18	* process may have the file descriptor open at a time. The calling
	19	* userspace program needs to keep the device file descriptor open
	20	* between the calls to write() and read() in order to preserve the
	21	* response. Up to 32 bytes will be available for reading.
	22	*
	23	* For testing purposes, try requesting the EC's firmware build
	24	* date, by sending the WILCO_EC_TELEM_GET_VERSION command with
	25	* argument index=3. i.e. write [0x38, 0x00, 0x03]
	26	* to the device node. An ASCII string of the build date is
	27	* returned.
	28	*/
	29
	30	#include <linux/cdev.h>
	31	#include <linux/device.h>
	32	#include <linux/fs.h>
	33	#include <linux/module.h>
	34	#include <linux/platform_data/wilco-ec.h>
	35	#include <linux/platform_device.h>
	36	#include <linux/slab.h>
	37	#include <linux/types.h>
	38	#include <linux/uaccess.h>
	39
	40	#define TELEM_DEV_NAME "wilco_telem"
	41	#define TELEM_CLASS_NAME TELEM_DEV_NAME
	42	#define DRV_NAME TELEM_DEV_NAME
	43	#define TELEM_DEV_NAME_FMT (TELEM_DEV_NAME "%d")
	44	static struct class telem_class = {
	45	.owner = THIS_MODULE,
	46	.name = TELEM_CLASS_NAME,
	47	};
	48
	49	/* Keep track of all the device numbers used. */
	50	#define TELEM_MAX_DEV 128
	51	static int telem_major;
	52	static DEFINE_IDA(telem_ida);
	53
	54	/* EC telemetry command codes */
	55	#define WILCO_EC_TELEM_GET_LOG 0x99
	56	#define WILCO_EC_TELEM_GET_VERSION 0x38
	57	#define WILCO_EC_TELEM_GET_FAN_INFO 0x2E
	58	#define WILCO_EC_TELEM_GET_DIAG_INFO 0xFA
	59	#define WILCO_EC_TELEM_GET_TEMP_INFO 0x95
	60	#define WILCO_EC_TELEM_GET_TEMP_READ 0x2C
	61	#define WILCO_EC_TELEM_GET_BATT_EXT_INFO 0x07
3b81d8bd	62	#define WILCO_EC_TELEM_GET_BATT_PPID_INFO 0x8A
1210d1e6 NC	63
	64	#define TELEM_ARGS_SIZE_MAX 30
	65
1210d1e6 NC	66	/*
	67	* The following telem_args_get_* structs are embedded within the \|args\| field
	68	* of wilco_ec_telem_request.
	69	*/
	70
	71	struct telem_args_get_log {
	72	u8 log_type;
	73	u8 log_index;
	74	} __packed;
	75
	76	/*
	77	* Get a piece of info about the EC firmware version:
	78	* 0 = label
	79	* 1 = svn_rev
	80	* 2 = model_no
	81	* 3 = build_date
	82	* 4 = frio_version
	83	*/
	84	struct telem_args_get_version {
	85	u8 index;
	86	} __packed;
	87
	88	struct telem_args_get_fan_info {
	89	u8 command;
	90	u8 fan_number;
	91	u8 arg;
	92	} __packed;
	93
	94	struct telem_args_get_diag_info {
	95	u8 type;
	96	u8 sub_type;
	97	} __packed;
	98
	99	struct telem_args_get_temp_info {
	100	u8 command;
	101	u8 index;
	102	u8 field;
	103	u8 zone;
	104	} __packed;
	105
	106	struct telem_args_get_temp_read {
	107	u8 sensor_index;
	108	} __packed;
	109
	110	struct telem_args_get_batt_ext_info {
	111	u8 var_args[5];
	112	} __packed;
	113
3b81d8bd NC	114	struct telem_args_get_batt_ppid_info {
	115	u8 always1; /* Should always be 1 */
	116	} __packed;
	117
	118	/**
	119	* struct wilco_ec_telem_request - Telemetry command and arguments sent to EC.
	120	* @command: One of WILCO_EC_TELEM_GET_* command codes.
	121	* @reserved: Must be 0.
	122	* @args: The first N bytes are one of telem_args_get_* structs, the rest is 0.
	123	*/
	124	struct wilco_ec_telem_request {
	125	u8 command;
	126	u8 reserved;
	127	union {
	128	u8 buf[TELEM_ARGS_SIZE_MAX];
	129	struct telem_args_get_log get_log;
	130	struct telem_args_get_version get_version;
	131	struct telem_args_get_fan_info get_fan_info;
	132	struct telem_args_get_diag_info get_diag_info;
	133	struct telem_args_get_temp_info get_temp_info;
	134	struct telem_args_get_temp_read get_temp_read;
	135	struct telem_args_get_batt_ext_info get_batt_ext_info;
	136	struct telem_args_get_batt_ppid_info get_batt_ppid_info;
	137	} args;
	138	} __packed;
	139
1210d1e6 NC	140	/**
	141	* check_telem_request() - Ensure that a request from userspace is valid.
	142	* @rq: Request buffer copied from userspace.
	143	* @size: Number of bytes copied from userspace.
	144	*
	145	* Return: 0 if valid, -EINVAL if bad command or reserved byte is non-zero,
	146	* -EMSGSIZE if the request is too long.
	147	*
	148	* We do not want to allow userspace to send arbitrary telemetry commands to
	149	* the EC. Therefore we check to ensure that
	150	* 1. The request follows the format of struct wilco_ec_telem_request.
3b81d8bd	151	* 2. The supplied command code is one of the allowlisted commands.
1210d1e6 NC	152	* 3. The request only contains the necessary data for the header and arguments.
	153	*/
	154	static int check_telem_request(struct wilco_ec_telem_request *rq,
	155	size_t size)
	156	{
	157	size_t max_size = offsetof(struct wilco_ec_telem_request, args);
	158
	159	if (rq->reserved)
	160	return -EINVAL;
	161
	162	switch (rq->command) {
	163	case WILCO_EC_TELEM_GET_LOG:
3b81d8bd	164	max_size += sizeof(rq->args.get_log);
1210d1e6 NC	165	break;
1210d1e6 NC	166	case WILCO_EC_TELEM_GET_VERSION:
3b81d8bd	167	max_size += sizeof(rq->args.get_version);
1210d1e6 NC	168	break;
1210d1e6 NC	169	case WILCO_EC_TELEM_GET_FAN_INFO:
3b81d8bd	170	max_size += sizeof(rq->args.get_fan_info);
1210d1e6 NC	171	break;
1210d1e6 NC	172	case WILCO_EC_TELEM_GET_DIAG_INFO:
3b81d8bd	173	max_size += sizeof(rq->args.get_diag_info);
1210d1e6 NC	174	break;
1210d1e6 NC	175	case WILCO_EC_TELEM_GET_TEMP_INFO:
3b81d8bd	176	max_size += sizeof(rq->args.get_temp_info);
1210d1e6 NC	177	break;
1210d1e6 NC	178	case WILCO_EC_TELEM_GET_TEMP_READ:
3b81d8bd	179	max_size += sizeof(rq->args.get_temp_read);
1210d1e6 NC	180	break;
1210d1e6 NC	181	case WILCO_EC_TELEM_GET_BATT_EXT_INFO:
3b81d8bd NC	182	max_size += sizeof(rq->args.get_batt_ext_info);
	183	break;
	184	case WILCO_EC_TELEM_GET_BATT_PPID_INFO:
	185	if (rq->args.get_batt_ppid_info.always1 != 1)
	186	return -EINVAL;
	187
	188	max_size += sizeof(rq->args.get_batt_ppid_info);
1210d1e6 NC	189	break;
	190	default:
	191	return -EINVAL;
	192	}
	193
	194	return (size <= max_size) ? 0 : -EMSGSIZE;
	195	}
	196
	197	/**
	198	* struct telem_device_data - Data for a Wilco EC device that queries telemetry.
	199	* @cdev: Char dev that userspace reads and polls from.
	200	* @dev: Device associated with the %cdev.
	201	* @ec: Wilco EC that we will be communicating with using the mailbox interface.
	202	* @available: Boolean of if the device can be opened.
	203	*/
	204	struct telem_device_data {
	205	struct device dev;
	206	struct cdev cdev;
	207	struct wilco_ec_device *ec;
	208	atomic_t available;
	209	};
	210
	211	#define TELEM_RESPONSE_SIZE EC_MAILBOX_DATA_SIZE
	212
	213	/**
	214	* struct telem_session_data - Data that exists between open() and release().
	215	* @dev_data: Pointer to get back to the device data and EC.
	216	* @request: Command and arguments sent to EC.
	217	* @response: Response buffer of data from EC.
	218	* @has_msg: Is there data available to read from a previous write?
	219	*/
	220	struct telem_session_data {
	221	struct telem_device_data *dev_data;
	222	struct wilco_ec_telem_request request;
	223	u8 response[TELEM_RESPONSE_SIZE];
	224	bool has_msg;
	225	};
	226
	227	/**
	228	* telem_open() - Callback for when the device node is opened.
	229	* @inode: inode for this char device node.
	230	* @filp: file for this char device node.
	231	*
	232	* We need to ensure that after writing a command to the device,
	233	* the same userspace process reads the corresponding result.
	234	* Therefore, we increment a refcount on opening the device, so that
	235	* only one process can communicate with the EC at a time.
	236	*
	237	* Return: 0 on success, or negative error code on failure.
	238	*/
	239	static int telem_open(struct inode inode, struct file filp)
	240	{
	241	struct telem_device_data *dev_data;
	242	struct telem_session_data *sess_data;
	243
	244	/* Ensure device isn't already open */
	245	dev_data = container_of(inode->i_cdev, struct telem_device_data, cdev);
	246	if (atomic_cmpxchg(&dev_data->available, 1, 0) == 0)
	247	return -EBUSY;
	248
	249	get_device(&dev_data->dev);
	250
	251	sess_data = kzalloc(sizeof(*sess_data), GFP_KERNEL);
	252	if (!sess_data) {
253	atomic_set(&dev_data->available, 1);
254	return -ENOMEM;
255	}
256	sess_data->dev_data = dev_data;
257	sess_data->has_msg = false;
258
dbc334fb	259	stream_open(inode, filp);
1210d1e6 NC	260	filp->private_data = sess_data;
	261
	262	return 0;
	263	}
	264
	265	static ssize_t telem_write(struct file filp, const char __user buf,
	266	size_t count, loff_t *pos)
	267	{
	268	struct telem_session_data *sess_data = filp->private_data;
	269	struct wilco_ec_message msg = {};
	270	int ret;
	271
	272	if (count > sizeof(sess_data->request))
	273	return -EMSGSIZE;
3b81d8bd	274	memset(&sess_data->request, 0, sizeof(sess_data->request));
1210d1e6 NC	275	if (copy_from_user(&sess_data->request, buf, count))
	276	return -EFAULT;
	277	ret = check_telem_request(&sess_data->request, count);
	278	if (ret < 0)
	279	return ret;
	280
	281	memset(sess_data->response, 0, sizeof(sess_data->response));
	282	msg.type = WILCO_EC_MSG_TELEMETRY;
	283	msg.request_data = &sess_data->request;
	284	msg.request_size = sizeof(sess_data->request);
	285	msg.response_data = sess_data->response;
	286	msg.response_size = sizeof(sess_data->response);
	287
	288	ret = wilco_ec_mailbox(sess_data->dev_data->ec, &msg);
	289	if (ret < 0)
	290	return ret;
	291	if (ret != sizeof(sess_data->response))
	292	return -EMSGSIZE;
	293
	294	sess_data->has_msg = true;
	295
	296	return count;
	297	}
	298
	299	static ssize_t telem_read(struct file filp, char __user buf, size_t count,
	300	loff_t *pos)
	301	{
	302	struct telem_session_data *sess_data = filp->private_data;
	303
	304	if (!sess_data->has_msg)
	305	return -ENODATA;
	306	if (count > sizeof(sess_data->response))
	307	return -EINVAL;
	308
	309	if (copy_to_user(buf, sess_data->response, count))
	310	return -EFAULT;
	311
	312	sess_data->has_msg = false;
	313
	314	return count;
	315	}
	316
	317	static int telem_release(struct inode inode, struct file filp)
	318	{
	319	struct telem_session_data *sess_data = filp->private_data;
	320
	321	atomic_set(&sess_data->dev_data->available, 1);
	322	put_device(&sess_data->dev_data->dev);
	323	kfree(sess_data);
	324
	325	return 0;
	326	}
	327
	328	static const struct file_operations telem_fops = {
	329	.open = telem_open,
	330	.write = telem_write,
	331	.read = telem_read,
	332	.release = telem_release,
	333	.llseek = no_llseek,
	334	.owner = THIS_MODULE,
	335	};
	336
	337	/**
	338	* telem_device_free() - Callback to free the telem_device_data structure.
339	* @d: The device embedded in our device data, which we have been ref counting.
340	*
341	* Once all open file descriptors are closed and the device has been removed,
342	* the refcount of the device will fall to 0 and this will be called.
343	*/
344	static void telem_device_free(struct device *d)
345	{
346	struct telem_device_data *dev_data;
347
348	dev_data = container_of(d, struct telem_device_data, dev);
349	kfree(dev_data);
350	}
351
352	/**
353	* telem_device_probe() - Callback when creating a new device.
354	* @pdev: platform device that we will be receiving telems from.
355	*
356	* This finds a free minor number for the device, allocates and initializes
357	* some device data, and creates a new device and char dev node.
358	*
359	* Return: 0 on success, negative error code on failure.
360	*/
361	static int telem_device_probe(struct platform_device *pdev)
362	{
363	struct telem_device_data *dev_data;
364	int error, minor;
365
366	/* Get the next available device number */
367	minor = ida_alloc_max(&telem_ida, TELEM_MAX_DEV-1, GFP_KERNEL);
368	if (minor < 0) {
369	error = minor;
a532149c	370	dev_err(&pdev->dev, "Failed to find minor number: %d\n", error);
1210d1e6 NC	371	return error;
	372	}
	373
	374	dev_data = kzalloc(sizeof(*dev_data), GFP_KERNEL);
	375	if (!dev_data) {
	376	ida_simple_remove(&telem_ida, minor);
	377	return -ENOMEM;
	378	}
	379
	380	/* Initialize the device data */
	381	dev_data->ec = dev_get_platdata(&pdev->dev);
	382	atomic_set(&dev_data->available, 1);
	383	platform_set_drvdata(pdev, dev_data);
	384
	385	/* Initialize the device */
	386	dev_data->dev.devt = MKDEV(telem_major, minor);
	387	dev_data->dev.class = &telem_class;
	388	dev_data->dev.release = telem_device_free;
	389	dev_set_name(&dev_data->dev, TELEM_DEV_NAME_FMT, minor);
	390	device_initialize(&dev_data->dev);
	391
	392	/* Initialize the character device and add it to userspace */;
	393	cdev_init(&dev_data->cdev, &telem_fops);
	394	error = cdev_device_add(&dev_data->cdev, &dev_data->dev);
	395	if (error) {
	396	put_device(&dev_data->dev);
	397	ida_simple_remove(&telem_ida, minor);
	398	return error;
	399	}
	400
	401	return 0;
	402	}
	403
	404	static int telem_device_remove(struct platform_device *pdev)
	405	{
	406	struct telem_device_data *dev_data = platform_get_drvdata(pdev);
	407
	408	cdev_device_del(&dev_data->cdev, &dev_data->dev);
1210d1e6	409	ida_simple_remove(&telem_ida, MINOR(dev_data->dev.devt));
856a0a6e	410	put_device(&dev_data->dev);
1210d1e6 NC	411
	412	return 0;
	413	}
	414
	415	static struct platform_driver telem_driver = {
	416	.probe = telem_device_probe,
	417	.remove = telem_device_remove,
	418	.driver = {
	419	.name = DRV_NAME,
	420	},
	421	};
	422
	423	static int __init telem_module_init(void)
	424	{
	425	dev_t dev_num = 0;
	426	int ret;
	427
	428	ret = class_register(&telem_class);
	429	if (ret) {
a532149c	430	pr_err(DRV_NAME ": Failed registering class: %d\n", ret);
1210d1e6 NC	431	return ret;
	432	}
	433
	434	/* Request the kernel for device numbers, starting with minor=0 */
	435	ret = alloc_chrdev_region(&dev_num, 0, TELEM_MAX_DEV, TELEM_DEV_NAME);
	436	if (ret) {
a532149c	437	pr_err(DRV_NAME ": Failed allocating dev numbers: %d\n", ret);
1210d1e6 NC	438	goto destroy_class;
	439	}
	440	telem_major = MAJOR(dev_num);
	441
	442	ret = platform_driver_register(&telem_driver);
	443	if (ret < 0) {
	444	pr_err(DRV_NAME ": Failed registering driver: %d\n", ret);
	445	goto unregister_region;
	446	}
	447
	448	return 0;
	449
	450	unregister_region:
	451	unregister_chrdev_region(MKDEV(telem_major, 0), TELEM_MAX_DEV);
	452	destroy_class:
	453	class_unregister(&telem_class);
	454	ida_destroy(&telem_ida);
	455	return ret;
	456	}
	457
	458	static void __exit telem_module_exit(void)
	459	{
	460	platform_driver_unregister(&telem_driver);
	461	unregister_chrdev_region(MKDEV(telem_major, 0), TELEM_MAX_DEV);
	462	class_unregister(&telem_class);
	463	ida_destroy(&telem_ida);
	464	}
	465
	466	module_init(telem_module_init);
	467	module_exit(telem_module_exit);
	468
	469	MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
	470	MODULE_DESCRIPTION("Wilco EC telemetry driver");
	471	MODULE_LICENSE("GPL");
	472	MODULE_ALIAS("platform:" DRV_NAME);