Re: [PATCH v6 3/4] platform/chrome: Add support for raw commands in debugfs

[Enric Balletbo Serra]

Hi Nick,
Missatge de Nick Crews <ncrews@xxxxxxxxxxxx> del dia dv., 8 de febr.
2019 a les 2:24:
>
> Add a debugfs attribute that allows sending raw commands to the EC.
> This is useful for development and debug but should not be enabled
> in a production environment.
>
> To test:
> Get the EC firmware build date
> First send the request command
> > echo 00 f0 38 00 03 00 > raw
> Then read the result. "12/21/18" is in the middle of the response
> > cat raw
> 00 31 32 2f 32 31 2f 31 38 00 00 0f 01 00 01 00  .12/21/18.......
>
> Get the EC firmware build date
> First send the request command
> > echo 00 f0 38 00 03 00 > raw
> Then read the result. "12/21/18" is in the middle of the response
> > cat raw
> 00 31 32 2f 32 31 2f 31 38 00 00 0f 01 00 01 00  .12/21/18.......
>
> Signed-off-by: Duncan Laurie <dlaurie@xxxxxxxxxx>
> Signed-off-by: Nick Crews <ncrews@xxxxxxxxxxxx>
> ---
>
> Changes in v6:
> - s/4.19/5.1/ for kernel version in documentation, since that is
>   the version this patch should land in.
> - Instead of requiring at least 3 bytes for msg type and command,
>   now just require two for msg type. We can skip the command.
> - Fixed error checking in probe() so that errors are hidden, without
>   causing more errors or unextpected behavior.
> - Some comment polishing.
> - In the core, actually unregister the debugfs child platform_device
>
> Changes in v5:
> - core now always continues regardless of debugfs failure
> - mv documentation to file header
> - Check for OOM
> - rm unneeded check if debug_info is allocqated
> - rm bogus comment
> - add space around "+"
> - rm WILCO_EC_FLAG_EXTENDED_DATA, that is already obvious from
>   wilco_ec_message.response_size
>
> Changes in v4:
> - Change debugfs driver to be a separate module
> - Change me email to @chromium.org from @google.com
> - Change CONFIG_WILCO_EC_SYSFS_RAW to
>   CONFIG_WILCO_EC_DEBUGFS
>
> Changes in v3:
> - Move the attribute to the debugfs system
> - Move the implementation to debugfs.c
> - Improve the raw hex parsing
> - Encapsulate global variables in one object
> - Add safety check when passing less than 3 bytes
> - Move documentation to debugfs-wilco-ec
>
> Changes in v2:
> - Add sysfs documentation
> - rm duplicate EC_MAILBOX_DATA_SIZE defs
> - Make docstrings follow kernel style
> - Fix tags in commit msg
> - Move Kconfig to subdirectory
> - Reading raw now includes ASCII translation
>
>  Documentation/ABI/testing/debugfs-wilco-ec |  23 ++
>  drivers/platform/chrome/wilco_ec/Kconfig   |  10 +
>  drivers/platform/chrome/wilco_ec/Makefile  |   2 +
>  drivers/platform/chrome/wilco_ec/core.c    |  14 ++
>  drivers/platform/chrome/wilco_ec/debugfs.c | 238 +++++++++++++++++++++
>  include/linux/platform_data/wilco-ec.h     |   2 +
>  6 files changed, 289 insertions(+)
>  create mode 100644 Documentation/ABI/testing/debugfs-wilco-ec
>  create mode 100644 drivers/platform/chrome/wilco_ec/debugfs.c
>
> diff --git a/Documentation/ABI/testing/debugfs-wilco-ec b/Documentation/ABI/testing/debugfs-wilco-ec
> new file mode 100644
> index 000000000000..f814f112e213
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-wilco-ec
> @@ -0,0 +1,23 @@
> +What:          /sys/kernel/debug/wilco_ec/raw
> +Date:          January 2019
> +KernelVersion: 5.1
> +Description:
> +               Write and read raw mailbox commands to the EC.
> +
> +               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
> +
> +               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...
> diff --git a/drivers/platform/chrome/wilco_ec/Kconfig b/drivers/platform/chrome/wilco_ec/Kconfig
> index 20945a301ec6..fb6d9ff33e41 100644
> --- a/drivers/platform/chrome/wilco_ec/Kconfig
> +++ b/drivers/platform/chrome/wilco_ec/Kconfig
> @@ -9,3 +9,13 @@ 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..ae86cae216fd 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 debugfs platform device that will get picked up 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..8b324bfe42cd
> --- /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 */
> +       const static int MAX_WORD_SIZE = 16;
> +       char tmp[MAX_WORD_SIZE + 1];

I got this warning:

  CC [M]  drivers/platform/chrome/wilco_ec/debugfs.o
drivers/platform/chrome/wilco_ec/debugfs.c: In function âparse_hex_sentenceâ:
drivers/platform/chrome/wilco_ec/debugfs.c:79:2: warning: ISO C90
forbids array âtmpâ whose size canât be evaluated [-Wvla]
  char tmp[MAX_WORD_SIZE + 1];
  ^~~~

Could you kindly fix and resend, please.

Thanks,
 Enric

> +       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 */
> +       if (ret < 2)
> +               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 = ret > 2 ? request_data[2] : 0;
> +       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@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Wilco EC debugfs driver");
> diff --git a/include/linux/platform_data/wilco-ec.h b/include/linux/platform_data/wilco-ec.h
> index 0feb4b520a54..5344975afa1a 100644
> --- a/include/linux/platform_data/wilco-ec.h
> +++ b/include/linux/platform_data/wilco-ec.h
> @@ -34,6 +34,7 @@
>   * @data_buffer: Buffer used for EC communication.  The same buffer
>   *               is used to hold the request and the response.
>   * @data_size: Size of the data buffer used for EC communication.
> + * @debugfs_pdev: The child platform_device used by the debugfs sub-driver.
>   */
>  struct wilco_ec_device {
>         struct device *dev;
> @@ -43,6 +44,7 @@ struct wilco_ec_device {
>         struct resource *io_packet;
>         void *data_buffer;
>         size_t data_size;
> +       struct platform_device *debugfs_pdev;
>  };
>
>  /**
> --
> 2.20.1.611.gfbb209baf1-goog
>