4 files changed, 264 insertions, 0 deletions

diff --git a/drivers/platform/chrome/wilco_ec/Kconfig b/drivers/platform/chrome/wilco_ec/Kconfig
index c6bc4e8f3062..4a119ced4d0c 100644
--- a/drivers/platform/chrome/wilco_ec/Kconfig
+++ b/drivers/platform/chrome/wilco_ec/Kconfig
@@ -8,3 +8,13 @@ config WILCO_EC
 
           To compile this driver as a module, choose M here: the
           module will be called wilco_ec.
+
+config WILCO_EC_DEBUGFS
+        tristate "Enable raw access to EC via debugfs"
+        depends on WILCO_EC
+        help
+          If you say Y here, you get support for sending raw commands to
+          the Wilco EC via debugfs.  These commands do not do any byte
+          manipulation and allow for testing arbitrary commands.  This
+          interface is intended for debug only and will not be present
+          on production devices.
diff --git a/drivers/platform/chrome/wilco_ec/Makefile b/drivers/platform/chrome/wilco_ec/Makefile
index 03b32301dc61..063e7fb4ea17 100644
--- a/drivers/platform/chrome/wilco_ec/Makefile
+++ b/drivers/platform/chrome/wilco_ec/Makefile
@@ -2,3 +2,5 @@
 
 wilco_ec-objs                           := core.o mailbox.o
 obj-$(CONFIG_WILCO_EC)                  += wilco_ec.o
+wilco_ec_debugfs-objs                   := debugfs.o
+obj-$(CONFIG_WILCO_EC_DEBUGFS)          += wilco_ec_debugfs.o
diff --git a/drivers/platform/chrome/wilco_ec/core.c b/drivers/platform/chrome/wilco_ec/core.c
index 20ecc580d108..af5fd288b63b 100644
--- a/drivers/platform/chrome/wilco_ec/core.c
+++ b/drivers/platform/chrome/wilco_ec/core.c
@@ -69,11 +69,25 @@ static int wilco_ec_probe(struct platform_device *pdev)
         cros_ec_lpc_mec_init(ec->io_packet->start,
                              ec->io_packet->start + EC_MAILBOX_DATA_SIZE);
 
+        /*
+         * Register a child device that will be found by the debugfs driver.
+         * Ignore failure.
+         */
+        ec->debugfs_pdev = platform_device_register_data(dev,
+                                                         "wilco-ec-debugfs",
+                                                         PLATFORM_DEVID_AUTO,
+                                                         NULL, 0);
+
         return 0;
 }
 
 static int wilco_ec_remove(struct platform_device *pdev)
 {
+        struct wilco_ec_device *ec = platform_get_drvdata(pdev);
+
+        if (ec->debugfs_pdev)
+                platform_device_unregister(ec->debugfs_pdev);
+
         /* Teardown cros_ec interface */
         cros_ec_lpc_mec_destroy();
 
diff --git a/drivers/platform/chrome/wilco_ec/debugfs.c b/drivers/platform/chrome/wilco_ec/debugfs.c
new file mode 100644
index 000000000000..c090db2cd5be
--- /dev/null
+++ b/drivers/platform/chrome/wilco_ec/debugfs.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * debugfs attributes for Wilco EC
+ *
+ * Copyright 2019 Google LLC
+ *
+ * There is only one attribute used for debugging, called raw.
+ * You can write a hexadecimal sentence to raw, and that series of bytes
+ * will be sent to the EC. Then, you can read the bytes of response
+ * by reading from raw.
+ *
+ * For writing:
+ * Bytes 0-1 indicate the message type:
+ *         00 F0 = Execute Legacy Command
+ *         00 F2 = Read/Write NVRAM Property
+ * Byte 2 provides the command code
+ * Bytes 3+ consist of the data passed in the request
+ *
+ * When referencing the EC interface spec, byte 2 corresponds to MBOX[0],
+ * byte 3 corresponds to MBOX[1], etc.
+ *
+ * At least three bytes are required, for the msg type and command,
+ * with additional bytes optional for additional data.
+ *
+ * Example:
+ * // Request EC info type 3 (EC firmware build date)
+ * $ echo 00 f0 38 00 03 00 > raw
+ * // View the result. The decoded ASCII result "12/21/18" is
+ * // included after the raw hex.
+ * $ cat raw
+ * 00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00  .12/21/18.8...
+ */
+
+#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 256 raw bytes will take up more space when represented as a hex string */
+#define FORMATTED_BUFFER_SIZE (EC_MAILBOX_DATA_SIZE_EXTENDED * 4)
+
+struct wilco_ec_debugfs {
+        struct wilco_ec_device *ec;
+        struct dentry *dir;
+        size_t response_size;
+        u8 raw_data[EC_MAILBOX_DATA_SIZE_EXTENDED];
+        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 for command */
+        if (ret < 3)
+                return -EINVAL;
+
+        /* Clear response data buffer */
+        memset(debug_info->raw_data, '\0', EC_MAILBOX_DATA_SIZE_EXTENDED);
+
+        msg.type = request_data[0] << 8 | request_data[1];
+        msg.flags = WILCO_EC_FLAG_RAW;
+        msg.command = request_data[2];
+        msg.request_data = ret > 3 ? request_data + 3 : 0;
+        msg.request_size = ret - 3;
+        msg.response_data = debug_info->raw_data;
+        msg.response_size = EC_MAILBOX_DATA_SIZE;
+
+        /* Telemetry commands use extended response data */
+        if (msg.type == WILCO_EC_MSG_TELEMETRY_LONG) {
+                msg.flags |= WILCO_EC_FLAG_EXTENDED_DATA;
+                msg.response_size = EC_MAILBOX_DATA_SIZE_EXTENDED;
+        }
+
+        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,
+                                             FORMATTED_BUFFER_SIZE, 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,
+        .llseek = no_llseek,
+};
+
+/**
+ * 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);
+        if (!debug_info->dir)
+                return 0;
+        debugfs_create_file("raw", 0644, debug_info->dir, NULL, &fops_raw);
+
+        return 0;
+}
+
+static int wilco_ec_debugfs_remove(struct platform_device *pdev)
+{
+        debugfs_remove_recursive(debug_info->dir);
+
+        return 0;
+}
+
+static struct platform_driver wilco_ec_debugfs_driver = {
+        .driver = {
+                .name = DRV_NAME,
+        },
+        .probe = wilco_ec_debugfs_probe,
+        .remove = wilco_ec_debugfs_remove,
+};
+
+module_platform_driver(wilco_ec_debugfs_driver);
+
+MODULE_ALIAS("platform:" DRV_NAME);
+MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Wilco EC debugfs driver");