// SPDX-License-Identifier: GPL-2.0
/*
 * debugfs attributes for Wilco EC
 *
 * Copyright 2019 Google LLC
 *
 * See Documentation/ABI/testing/debugfs-wilco-ec for usage.
 */

#include <linux/ctype.h>
#include <linux/debugfs.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/platform_device.h>

#define DRV_NAME "wilco-ec-debugfs"

/* The raw bytes will take up more space when represented as a hex string */
#define FORMATTED_BUFFER_SIZE (EC_MAILBOX_DATA_SIZE * 4)

struct wilco_ec_debugfs {
        struct wilco_ec_device *ec;
        struct dentry *dir;
        size_t response_size;
        u8 raw_data[EC_MAILBOX_DATA_SIZE];
        u8 formatted_data[FORMATTED_BUFFER_SIZE];
};
static struct wilco_ec_debugfs *debug_info;

/**
 * parse_hex_sentence() - Convert a ascii hex representation into byte array.
 * @in: Input buffer of ascii.
 * @isize: Length of input buffer.
 * @out: Output buffer.
 * @osize: Length of output buffer, e.g. max number of bytes to parse.
 *
 * An valid input is a series of ascii hexadecimal numbers, separated by spaces.
 * An example valid input is
 * "   00 f2 0    000076 6 0  ff"
 *
 * If an individual "word" within the hex sentence is longer than MAX_WORD_SIZE,
 * then the sentence is illegal, and parsing will fail.
 *
 * Return: Number of bytes parsed, or negative error code on failure.
 */
static int parse_hex_sentence(const char *in, int isize, u8 *out, int osize)
{
        int n_parsed = 0;
        int word_start = 0;
        int word_end;
        int word_len;
        /* Temp buffer for holding a "word" of chars that represents one byte */
        #define MAX_WORD_SIZE 16
        char tmp[MAX_WORD_SIZE + 1];
        u8 byte;

        while (word_start < isize && n_parsed < osize) {
                /* Find the start of the next word */
                while (word_start < isize && isspace(in[word_start]))
                        word_start++;
                 /* reached the end of the input before next word? */
                if (word_start >= isize)
                        break;

                /* Find the end of this word */
                word_end = word_start;
                while (word_end < isize && !isspace(in[word_end]))
                        word_end++;

                /* Copy to a tmp NULL terminated string */
                word_len = word_end - word_start;
                if (word_len > MAX_WORD_SIZE)
                        return -EINVAL;
                memcpy(tmp, in + word_start, word_len);
                tmp[word_len] = '\0';

                /*
                 * Convert from hex string, place in output. If fails to parse,
                 * just return -EINVAL because specific error code is only
                 * relevant for this one word, returning it would be confusing.
                 */
                if (kstrtou8(tmp, 16, &byte))
                        return -EINVAL;
                out[n_parsed++] = byte;

                word_start = word_end;
        }
        return n_parsed;
}

/* The message type takes up two bytes*/
#define TYPE_AND_DATA_SIZE ((EC_MAILBOX_DATA_SIZE) + 2)

static ssize_t raw_write(struct file *file, const char __user *user_buf,
                         size_t count, loff_t *ppos)
{
        char *buf = debug_info->formatted_data;
        struct wilco_ec_message msg;
        u8 request_data[TYPE_AND_DATA_SIZE];
        ssize_t kcount;
        int ret;

        if (count > FORMATTED_BUFFER_SIZE)
                return -EINVAL;

        kcount = simple_write_to_buffer(buf, FORMATTED_BUFFER_SIZE, ppos,
                                        user_buf, count);
        if (kcount < 0)
                return kcount;

        ret = parse_hex_sentence(buf, kcount, request_data, TYPE_AND_DATA_SIZE);
        if (ret < 0)
                return ret;
        /* Need at least two bytes for message type and one byte of data */
        if (ret < 3)
                return -EINVAL;

        msg.type = request_data[0] << 8 | request_data[1];
        msg.flags = 0;
        msg.request_data = request_data + 2;
        msg.request_size = ret - 2;
        memset(debug_info->raw_data, 0, sizeof(debug_info->raw_data));
        msg.response_data = debug_info->raw_data;
        msg.response_size = EC_MAILBOX_DATA_SIZE;

        ret = wilco_ec_mailbox(debug_info->ec, &msg);
        if (ret < 0)
                return ret;
        debug_info->response_size = ret;

        return count;
}

static ssize_t raw_read(struct file *file, char __user *user_buf, size_t count,
                        loff_t *ppos)
{
        int fmt_len = 0;

        if (debug_info->response_size) {
                fmt_len = hex_dump_to_buffer(debug_info->raw_data,
                                             debug_info->response_size,
                                             16, 1, debug_info->formatted_data,
                                             sizeof(debug_info->formatted_data),
                                             true);
                /* Only return response the first time it is read */
                debug_info->response_size = 0;
        }

        return simple_read_from_buffer(user_buf, count, ppos,
                                       debug_info->formatted_data, fmt_len);
}

static const struct file_operations fops_raw = {
        .owner = THIS_MODULE,
        .read = raw_read,
        .write = raw_write,
};

#define CMD_KB_CHROME           0x88
#define SUB_CMD_H1_GPIO         0x0A
#define SUB_CMD_TEST_EVENT      0x0B

struct ec_request {
        u8 cmd;         /* Always CMD_KB_CHROME */
        u8 reserved;
        u8 sub_cmd;
} __packed;

struct ec_response {
        u8 status;      /* 0 if allowed */
        u8 val;
} __packed;

static int send_ec_cmd(struct wilco_ec_device *ec, u8 sub_cmd, u8 *out_val)
{
        struct ec_request rq;
        struct ec_response rs;
        struct wilco_ec_message msg;
        int ret;

        memset(&rq, 0, sizeof(rq));
        rq.cmd = CMD_KB_CHROME;
        rq.sub_cmd = sub_cmd;

        memset(&msg, 0, sizeof(msg));
        msg.type = WILCO_EC_MSG_LEGACY;
        msg.request_data = &rq;
        msg.request_size = sizeof(rq);
        msg.response_data = &rs;
        msg.response_size = sizeof(rs);
        ret = wilco_ec_mailbox(ec, &msg);
        if (ret < 0)
                return ret;
        if (rs.status)
                return -EIO;

        *out_val = rs.val;

        return 0;
}

/**
 * h1_gpio_get() - Gets h1 gpio status.
 * @arg: The wilco EC device.
 * @val: BIT(0)=ENTRY_TO_FACT_MODE, BIT(1)=SPI_CHROME_SEL
 */
static int h1_gpio_get(void *arg, u64 *val)
{
        int ret;

        ret = send_ec_cmd(arg, SUB_CMD_H1_GPIO, (u8 *)val);
        if (ret == 0)
                *val &= 0xFF;
        return ret;
}

DEFINE_DEBUGFS_ATTRIBUTE(fops_h1_gpio, h1_gpio_get, NULL, "0x%02llx\n");

/**
 * test_event_set() - Sends command to EC to cause an EC test event.
 * @arg: The wilco EC device.
 * @val: unused.
 */
static int test_event_set(void *arg, u64 val)
{
        u8 ret;

        return send_ec_cmd(arg, SUB_CMD_TEST_EVENT, &ret);
}

/* Format is unused since it is only required for get method which is NULL */
DEFINE_DEBUGFS_ATTRIBUTE(fops_test_event, NULL, test_event_set, "%llu\n");

/**
 * wilco_ec_debugfs_probe() - Create the debugfs node
 * @pdev: The platform device, probably created in core.c
 *
 * Try to create a debugfs node. If it fails, then we don't want to change
 * behavior at all, this is for debugging after all. Just fail silently.
 *
 * Return: 0 always.
 */
static int wilco_ec_debugfs_probe(struct platform_device *pdev)
{
        struct wilco_ec_device *ec = dev_get_drvdata(pdev->dev.parent);

        debug_info = devm_kzalloc(&pdev->dev, sizeof(*debug_info), GFP_KERNEL);
        if (!debug_info)
                return 0;
        debug_info->ec = ec;
        debug_info->dir = debugfs_create_dir("wilco_ec", NULL);
        debugfs_create_file("raw", 0644, debug_info->dir, NULL, &fops_raw);
        debugfs_create_file("h1_gpio", 0444, debug_info->dir, ec,
                            &fops_h1_gpio);
        debugfs_create_file("test_event", 0200, debug_info->dir, ec,
                            &fops_test_event);

        return 0;
}

static void wilco_ec_debugfs_remove(struct platform_device *pdev)
{
        debugfs_remove_recursive(debug_info->dir);
}

static const struct platform_device_id wilco_ec_debugfs_id[] = {
        { DRV_NAME, 0 },
        {}
};
MODULE_DEVICE_TABLE(platform, wilco_ec_debugfs_id);

static struct platform_driver wilco_ec_debugfs_driver = {
        .driver = {
                .name = DRV_NAME,
        },
        .probe = wilco_ec_debugfs_probe,
        .remove = wilco_ec_debugfs_remove,
        .id_table = wilco_ec_debugfs_id,
};

module_platform_driver(wilco_ec_debugfs_driver);

MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Wilco EC debugfs driver");