Re: [PATCH v4 03/11] mfd / platform: cros_ec: Miscellaneous character device to talk with the EC

[Enric Balletbo i Serra]

Hi Gwendal,

On 15/7/19 19:08, Gwendal Grignou wrote:
> On Thu, Jun 27, 2019 at 3:40 AM Enric Balletbo i Serra
> <enric.balletbo@xxxxxxxxxxxxx> wrote:
>>
>> That's a driver to talk with the ChromeOS Embedded Controller via a
>> miscellaneous character device, it creates an entry in /dev for every
>> instance and implements basic file operations for communicating with the
>> Embedded Controller with an userspace application. The API is moved to
>> the uapi folder, which is supposed to contain the user space API of the
>> kernel.
>>
>> Note that this will replace current character device interface
>> implemented in the cros-ec-dev driver in the MFD subsystem. The idea is
>> to move all the functionality that extends the bounds of what MFD was
>> designed to platform/chrome subsystem.
>>
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
>> Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
>> Tested-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
>> ---
>>
>> Changes in v4: None
>> Changes in v3:
>> - Fix 'linux/mfd/cros_ec.h' is not exported (reported by lkp)
>>
>> Changes in v2:
>> - Remove the list, and the lock, as are not needed (Greg Kroah-Hartman)
>> - Remove dev_info in probe, anyway we will see the chardev or not if the
>>   probe fails (Greg Kroah-Hartman)
>>
>>  Documentation/ioctl/ioctl-number.txt          |   2 +-
>>  drivers/mfd/cros_ec_dev.c                     |   4 +-
>>  drivers/platform/chrome/Kconfig               |  11 +
>>  drivers/platform/chrome/Makefile              |   1 +
>>  drivers/platform/chrome/cros_ec_chardev.c     | 253 ++++++++++++++++++
>>  .../uapi/linux/cros_ec_chardev.h              |  21 +-
>>  6 files changed, 273 insertions(+), 19 deletions(-)
>>  create mode 100644 drivers/platform/chrome/cros_ec_chardev.c
>>  rename drivers/mfd/cros_ec_dev.h => include/uapi/linux/cros_ec_chardev.h (50%)
>>
>> diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
>> index c9558146ac58..8bd7907ee36d 100644
>> --- a/Documentation/ioctl/ioctl-number.txt
>> +++ b/Documentation/ioctl/ioctl-number.txt
>> @@ -340,7 +340,7 @@ Code  Seq#(hex)     Include File            Comments
>>  0xDD   00-3F   ZFCP device driver      see drivers/s390/scsi/
>>                                         <mailto:aherrman@xxxxxxxxxx>
>>  0xE5   00-3F   linux/fuse.h
>> -0xEC   00-01   drivers/platform/chrome/cros_ec_dev.h   ChromeOS EC driver
>> +0xEC   00-01   include/uapi/linux/cros_ec_chardev.h    ChromeOS EC driver
>>  0xF3   00-3F   drivers/usb/misc/sisusbvga/sisusb.h     sisfb (in development)
>>                                         <mailto:thomas@xxxxxxxxxxxxxxxx>
>>  0xF4   00-1F   video/mbxfb.h           mbxfb
>> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
>> index eb77bf6406f3..3334bc4e42ee 100644
>> --- a/drivers/mfd/cros_ec_dev.c
>> +++ b/drivers/mfd/cros_ec_dev.c
>> @@ -19,6 +19,8 @@
>>
>>  #include <linux/fs.h>
>>  #include <linux/mfd/core.h>
>> +#include <linux/mfd/cros_ec.h>
>> +#include <linux/mfd/cros_ec_commands.h>
>>  #include <linux/module.h>
>>  #include <linux/mod_devicetable.h>
>>  #include <linux/of_platform.h>
>> @@ -27,7 +29,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/uaccess.h>
>>
>> -#include "cros_ec_dev.h"
>> +#include <uapi/linux/cros_ec_chardev.h>
>>
>>  #define DRV_NAME "cros-ec-dev"
>>
>> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
>> index 1e7a10500b3f..221e709358c0 100644
>> --- a/drivers/platform/chrome/Kconfig
>> +++ b/drivers/platform/chrome/Kconfig
>> @@ -133,6 +133,17 @@ config CROS_KBD_LED_BACKLIGHT
>>           To compile this driver as a module, choose M here: the
>>           module will be called cros_kbd_led_backlight.
>>
>> +config CROS_EC_CHARDEV
>> +       tristate "ChromeOS EC miscdevice"
>> +       depends on MFD_CROS_EC_CHARDEV
>> +       default MFD_CROS_EC_CHARDEV
>> +       help
>> +         This driver adds file operations support to talk with the
>> +         ChromeOS EC from userspace via a character device.
>> +
>> +         To compile this driver as a module, choose M here: the
>> +         module will be called cros_ec_chardev.
>> +
>>  config CROS_EC_LIGHTBAR
>>         tristate "Chromebook Pixel's lightbar support"
>>         depends on MFD_CROS_EC_CHARDEV
>> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
>> index f69e0be98bd6..e6758e967ac5 100644
>> --- a/drivers/platform/chrome/Makefile
>> +++ b/drivers/platform/chrome/Makefile
>> @@ -15,6 +15,7 @@ cros_ec_lpcs-$(CONFIG_CROS_EC_LPC_MEC)        += cros_ec_lpc_mec.o
>>  obj-$(CONFIG_CROS_EC_LPC)              += cros_ec_lpcs.o
>>  obj-$(CONFIG_CROS_EC_PROTO)            += cros_ec_proto.o cros_ec_trace.o
>>  obj-$(CONFIG_CROS_KBD_LED_BACKLIGHT)   += cros_kbd_led_backlight.o
>> +obj-$(CONFIG_CROS_EC_CHARDEV)          += cros_ec_chardev.o
>>  obj-$(CONFIG_CROS_EC_LIGHTBAR)         += cros_ec_lightbar.o
>>  obj-$(CONFIG_CROS_EC_VBC)              += cros_ec_vbc.o
>>  obj-$(CONFIG_CROS_EC_DEBUGFS)          += cros_ec_debugfs.o
>> diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c
>> new file mode 100644
>> index 000000000000..ce77839b0dcb
>> --- /dev/null
>> +++ b/drivers/platform/chrome/cros_ec_chardev.c
>> @@ -0,0 +1,253 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Miscellaneous character driver for ChromeOS Embedded Controller
>> + *
>> + * Copyright 2014 Google, Inc.
>> + * Copyright 2019 Google LLC
>> + *
>> + * This file is a rework and part of the code is ported from
>> + * drivers/mfd/cros_ec_dev.c that was originally written by
>> + * Bill Richardson.
>> + */
>> +
>> +#include <linux/init.h>
>> +#include <linux/device.h>
>> +#include <linux/fs.h>
>> +#include <linux/mfd/cros_ec.h>
>> +#include <linux/mfd/cros_ec_commands.h>
>> +#include <linux/miscdevice.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +#include <linux/types.h>
>> +#include <linux/uaccess.h>
>> +
>> +#include <uapi/linux/cros_ec_chardev.h>
>> +
>> +#define DRV_NAME               "cros-ec-chardev"
>> +
>> +struct chardev_data {
>> +       struct cros_ec_dev *ec_dev;
>> +       struct miscdevice misc;
>> +};
>> +
>> +static int ec_get_version(struct cros_ec_dev *ec, char *str, int maxlen)
>> +{
>> +       static const char * const current_image_name[] = {
>> +               "unknown", "read-only", "read-write", "invalid",
>> +       };
>> +       struct ec_response_get_version *resp;
>> +       struct cros_ec_command *msg;
>> +       int ret;
>> +
>> +       msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
>> +       if (!msg)
>> +               return -ENOMEM;
>> +
>> +       msg->command = EC_CMD_GET_VERSION + ec->cmd_offset;
>> +       msg->insize = sizeof(*resp);
>> +
>> +       ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
>> +       if (ret < 0) {
>> +               snprintf(str, maxlen,
>> +                        "Unknown EC version, returned error: %d\n",
>> +                        msg->result);
>> +               goto exit;
>> +       }
>> +
>> +       resp = (struct ec_response_get_version *)msg->data;
>> +       if (resp->current_image >= ARRAY_SIZE(current_image_name))
>> +               resp->current_image = 3; /* invalid */
>> +
>> +       snprintf(str, maxlen, "%s\n%s\n%s\n",
> We need to keep the same output as it was implemented in
> ec_get_version in cros_ec_dev.c [See "mfd: cros_ec: Switch to use the
> new cros-ec-chardev driver"]:
> In particular, we need to prefix the versions strings with
> CROS_EC_DEV_VERSION ["1.0.0"], as user space tools are relying on that
> marker to keep going.

Ok, I'll modify this and send a new version rebased on top of rc1 when released.

Thanks,
~ Enric


>> +                resp->version_string_ro,
>> +                resp->version_string_rw,
>> +                current_image_name[resp->current_image]);
>> +
>> +       ret = 0;
>> +exit:
>> +       kfree(msg);
>> +       return ret;
>> +}
>> +
>> +/*
>> + * Device file ops
>> + */
>> +static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
>> +{
>> +       struct miscdevice *mdev = filp->private_data;
>> +       struct cros_ec_dev *ec_dev = dev_get_drvdata(mdev->parent);
>> +
>> +       filp->private_data = ec_dev;
>> +       nonseekable_open(inode, filp);
>> +
>> +       return 0;
>> +}
>> +
>> +static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
>> +                                    size_t length, loff_t *offset)
>> +{
>> +       char msg[sizeof(struct ec_response_get_version) +
>> +                sizeof(CROS_EC_DEV_VERSION)];
>> +       struct cros_ec_dev *ec = filp->private_data;
>> +       size_t count;
>> +       int ret;
>> +
>> +       if (*offset != 0)
>> +               return 0;
>> +
>> +       ret = ec_get_version(ec, msg, sizeof(msg));
>> +       if (ret)
>> +               return ret;
>> +
>> +       count = min(length, strlen(msg));
>> +
>> +       if (copy_to_user(buffer, msg, count))
>> +               return -EFAULT;
>> +
>> +       *offset = count;
>> +       return count;
>> +}
>> +
>> +/*
>> + * Ioctls
>> + */
>> +static long cros_ec_chardev_ioctl_xcmd(struct cros_ec_dev *ec, void __user *arg)
>> +{
>> +       struct cros_ec_command *s_cmd;
>> +       struct cros_ec_command u_cmd;
>> +       long ret;
>> +
>> +       if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
>> +               return -EFAULT;
>> +
>> +       if (u_cmd.outsize > EC_MAX_MSG_BYTES ||
>> +           u_cmd.insize > EC_MAX_MSG_BYTES)
>> +               return -EINVAL;
>> +
>> +       s_cmd = kmalloc(sizeof(*s_cmd) + max(u_cmd.outsize, u_cmd.insize),
>> +                       GFP_KERNEL);
>> +       if (!s_cmd)
>> +               return -ENOMEM;
>> +
>> +       if (copy_from_user(s_cmd, arg, sizeof(*s_cmd) + u_cmd.outsize)) {
>> +               ret = -EFAULT;
>> +               goto exit;
>> +       }
>> +
>> +       if (u_cmd.outsize != s_cmd->outsize ||
>> +           u_cmd.insize != s_cmd->insize) {
>> +               ret = -EINVAL;
>> +               goto exit;
>> +       }
>> +
>> +       s_cmd->command += ec->cmd_offset;
>> +       ret = cros_ec_cmd_xfer(ec->ec_dev, s_cmd);
>> +       /* Only copy data to userland if data was received. */
>> +       if (ret < 0)
>> +               goto exit;
>> +
>> +       if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
>> +               ret = -EFAULT;
>> +exit:
>> +       kfree(s_cmd);
>> +       return ret;
>> +}
>> +
>> +static long cros_ec_chardev_ioctl_readmem(struct cros_ec_dev *ec,
>> +                                          void __user *arg)
>> +{
>> +       struct cros_ec_device *ec_dev = ec->ec_dev;
>> +       struct cros_ec_readmem s_mem = { };
>> +       long num;
>> +
>> +       /* Not every platform supports direct reads */
>> +       if (!ec_dev->cmd_readmem)
>> +               return -ENOTTY;
>> +
>> +       if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
>> +               return -EFAULT;
>> +
>> +       num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
>> +                                 s_mem.buffer);
>> +       if (num <= 0)
>> +               return num;
>> +
>> +       if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
>> +               return -EFAULT;
>> +
>> +       return num;
>> +}
>> +
>> +static long cros_ec_chardev_ioctl(struct file *filp, unsigned int cmd,
>> +                                  unsigned long arg)
>> +{
>> +       struct cros_ec_dev *ec = filp->private_data;
>> +
>> +       if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
>> +               return -ENOTTY;
>> +
>> +       switch (cmd) {
>> +       case CROS_EC_DEV_IOCXCMD:
>> +               return cros_ec_chardev_ioctl_xcmd(ec, (void __user *)arg);
>> +       case CROS_EC_DEV_IOCRDMEM:
>> +               return cros_ec_chardev_ioctl_readmem(ec, (void __user *)arg);
>> +       }
>> +
>> +       return -ENOTTY;
>> +}
>> +
>> +static const struct file_operations chardev_fops = {
>> +       .open           = cros_ec_chardev_open,
>> +       .read           = cros_ec_chardev_read,
>> +       .unlocked_ioctl = cros_ec_chardev_ioctl,
>> +#ifdef CONFIG_COMPAT
>> +       .compat_ioctl   = cros_ec_chardev_ioctl,
>> +#endif
>> +};
>> +
>> +static int cros_ec_chardev_probe(struct platform_device *pdev)
>> +{
>> +       struct cros_ec_dev *ec_dev = dev_get_drvdata(pdev->dev.parent);
>> +       struct cros_ec_platform *ec_platform = dev_get_platdata(ec_dev->dev);
>> +       struct chardev_data *data;
>> +
>> +       /* Create a char device: we want to create it anew */
>> +       data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
>> +       if (!data)
>> +               return -ENOMEM;
>> +
>> +       data->ec_dev = ec_dev;
>> +       data->misc.minor = MISC_DYNAMIC_MINOR;
>> +       data->misc.fops = &chardev_fops;
>> +       data->misc.name = ec_platform->ec_name;
>> +       data->misc.parent = pdev->dev.parent;
>> +
>> +       dev_set_drvdata(&pdev->dev, data);
>> +
>> +       return misc_register(&data->misc);
>> +}
>> +
>> +static int cros_ec_chardev_remove(struct platform_device *pdev)
>> +{
>> +       struct chardev_data *data = dev_get_drvdata(&pdev->dev);
>> +
>> +       misc_deregister(&data->misc);
>> +
>> +       return 0;
>> +}
>> +
>> +static struct platform_driver cros_ec_chardev_driver = {
>> +       .driver = {
>> +               .name = DRV_NAME,
>> +       },
>> +       .probe = cros_ec_chardev_probe,
>> +       .remove = cros_ec_chardev_remove,
>> +};
>> +
>> +module_platform_driver(cros_ec_chardev_driver);
>> +
>> +MODULE_ALIAS("platform:" DRV_NAME);
>> +MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>");
>> +MODULE_DESCRIPTION("ChromeOS EC Miscellaneous Character Driver");
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/mfd/cros_ec_dev.h b/include/uapi/linux/cros_ec_chardev.h
>> similarity index 50%
>> rename from drivers/mfd/cros_ec_dev.h
>> rename to include/uapi/linux/cros_ec_chardev.h
>> index ec750433455a..8aceb4ac8ec5 100644
>> --- a/drivers/mfd/cros_ec_dev.h
>> +++ b/include/uapi/linux/cros_ec_chardev.h
>> @@ -1,28 +1,15 @@
>> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
>>  /*
>> - * cros_ec_dev - expose the Chrome OS Embedded Controller to userspace
>> + * ChromeOS EC device interface.
>>   *
>>   * Copyright (C) 2014 Google, Inc.
>> - *
>> - * This program is free software; you can redistribute it and/or modify
>> - * it under the terms of the GNU General Public License as published by
>> - * the Free Software Foundation; either version 2 of the License, or
>> - * (at your option) any later version.
>> - *
>> - * This program is distributed in the hope that it will be useful,
>> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>> - * GNU General Public License for more details.
>> - *
>> - * You should have received a copy of the GNU General Public License
>> - * along with this program. If not, see <http://www.gnu.org/licenses/>.
>>   */
>>
>> -#ifndef _CROS_EC_DEV_H_
>> -#define _CROS_EC_DEV_H_
>> +#ifndef _UAPI_LINUX_CROS_EC_DEV_H_
>> +#define _UAPI_LINUX_CROS_EC_DEV_H_
>>
>>  #include <linux/ioctl.h>
>>  #include <linux/types.h>
>> -#include <linux/mfd/cros_ec.h>
>>
>>  #define CROS_EC_DEV_VERSION "1.0.0"
>>
>> --
>> 2.20.1
>>