Date:	Tue, 13 Jan 2015 15:40:07 -0800
From:	Gwendal Grignou <gwendal@...omium.org>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Lee Jones <lee.jones@...aro.org>, Olof Johansson <olof@...om.net>,
	Doug Anderson <dianders@...omium.org>,
	Bill Richardson <wfrichar@...omium.org>,
	Simon Glass <sjg@...gle.com>, Jonathan Corbet <corbet@....net>,
	linux-samsung-soc@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND v2 4/7] platform/chrome: Add Chrome OS EC userspace
 device interface

On Fri, Jan 2, 2015 at 5:32 AM, Javier Martinez Canillas
<javier.martinez@...labora.co.uk> wrote:
>
> From: Bill Richardson <wfrichar@...omium.org>
>
> This patch adds a device interface to access the
> Chrome OS Embedded Controller from user-space.
>
> Signed-off-by: Bill Richardson <wfrichar@...omium.org>
> Reviewed-by: Simon Glass <sjg@...gle.com>
> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Reviewed-by: Gwendal Grignou <gwendal@...omium.org>
> ---
>
> Changes since v1:
>  - The cros_ec_dev driver does not belong to drivers/mfd (Lee Jones)
>  - Don't call class_create in the probe function (Gwendal Grignou)
>  - Don't use the deprecated register_chrdev() function (Gwendal Grignou)
>  - Remove struct cros_ec_device *ec global variable (Lee Jones)
>  - Arrange structures to be 64-bit safe instead using the IOCTL compact API
>    (Alan Cox)
>  - Use _CHARDEV instead of _DEV as a postfix to denote that is a character
>    device user-space interface (Lee Jones)
>  - Remove the CROS_CLASS_NAME define and just use the name directly (Lee Jones)
>  - Remove unncessary include headers (Lee Jones)
>  - Add a newline when appropiate and remove double new lines (Lee Jones)
>  - If *offset == 0, there is no need to do *offset +=, just use = (Lee Jones)
>  - Use dev_err() instead of pr_err() when possible (Lee Jones)
>  - Remove unnecesary goto and just return an error instead (Lee Jones)
>  - Don't set .owner to THIS_MODULE since that is made by the core (Lee Jones)
>  - Document the ioctl number used in Documentation/ioctl/ioctl-number.txt
>
>  Documentation/ioctl/ioctl-number.txt  |   1 +
>  drivers/platform/chrome/Kconfig       |  14 +-
>  drivers/platform/chrome/Makefile      |   1 +
>  drivers/platform/chrome/cros_ec_dev.c | 268 ++++++++++++++++++++++++++++++++++
>  drivers/platform/chrome/cros_ec_dev.h |  47 ++++++
>  5 files changed, 328 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/platform/chrome/cros_ec_dev.c
>  create mode 100644 drivers/platform/chrome/cros_ec_dev.h
>
> diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
> index 8136e1f..51f4221 100644
> --- a/Documentation/ioctl/ioctl-number.txt
> +++ b/Documentation/ioctl/ioctl-number.txt
> @@ -321,6 +321,7 @@ Code  Seq#(hex)     Include File            Comments
>  0xDB   00-0F   drivers/char/mwave/mwavepub.h
>  0xDD   00-3F   ZFCP device driver      see drivers/s390/scsi/
>                                         <mailto:aherrman@...ibm.com>
> +0xEC   00-01   drivers/platform/chrome/cros_ec_dev.h   ChromeOS EC driver
>  0xF3   00-3F   drivers/usb/misc/sisusbvga/sisusb.h     sisfb (in development)
>                                         <mailto:thomas@...ischhofer.net>
>  0xF4   00-1F   video/mbxfb.h           mbxfb
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index 440ed77..75dc514 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -4,7 +4,7 @@
>
>  menuconfig CHROME_PLATFORMS
>         bool "Platform support for Chrome hardware"
> -       depends on X86
> +       depends on X86 || ARM
>         ---help---
>           Say Y here to get to see options for platform support for
>           various Chromebooks and Chromeboxes. This option alone does
> @@ -16,8 +16,7 @@ if CHROME_PLATFORMS
>
>  config CHROMEOS_LAPTOP
>         tristate "Chrome OS Laptop"
> -       depends on I2C
> -       depends on DMI
> +       depends on I2C && DMI && X86
>         ---help---
>           This driver instantiates i2c and smbus devices such as
>           light sensors and touchpads.
> @@ -27,6 +26,7 @@ config CHROMEOS_LAPTOP
>
>  config CHROMEOS_PSTORE
>         tristate "Chrome OS pstore support"
> +       depends on X86
>         ---help---
>           This module instantiates the persistent storage on x86 ChromeOS
>           devices. It can be used to store away console logs and crash
> @@ -38,5 +38,13 @@ config CHROMEOS_PSTORE
>           If you have a supported Chromebook, choose Y or M here.
>           The module will be called chromeos_pstore.
>
> +config CROS_EC_CHARDEV
> +        tristate "Chrome OS Embedded Controller userspace device interface"
> +        depends on MFD_CROS_EC
> +        ---help---
> +          This driver adds support to talk with the ChromeOS EC from userspace.
> +
> +          If you have a supported Chromebook, choose Y or M here.
> +          The module will be called cros_ec_dev.
>
>  endif # CHROMEOS_PLATFORMS
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index 2b860ca..10f1361 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -1,3 +1,4 @@
>
>  obj-$(CONFIG_CHROMEOS_LAPTOP)  += chromeos_laptop.o
>  obj-$(CONFIG_CHROMEOS_PSTORE)  += chromeos_pstore.o
> +obj-$(CONFIG_CROS_EC_CHARDEV)  += cros_ec_dev.o
> diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
> new file mode 100644
> index 0000000..04cc8eb
> --- /dev/null
> +++ b/drivers/platform/chrome/cros_ec_dev.c
> @@ -0,0 +1,268 @@
> +/*
> + * cros_ec_dev - expose the Chrome OS Embedded Controller to user-space
> + *
> + * 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/>.
> + */
> +
> +#include <linux/fs.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +
> +#include "cros_ec_dev.h"
> +
> +/* Device variables */
> +#define CROS_MAX_DEV 128
> +static struct class *cros_class;
> +static int ec_major;
> +
> +/* Basic communication */
> +static int ec_get_version(struct cros_ec_device *ec, char *str, int maxlen)
> +{
> +       struct ec_response_get_version *resp;
> +       static const char * const current_image_name[] = {
> +               "unknown", "read-only", "read-write", "invalid",
> +       };
> +       struct cros_ec_command msg = {
> +               .version = 0,
> +               .command = EC_CMD_GET_VERSION,
> +               .outdata = { 0 },
> +               .outsize = 0,
> +               .indata = { 0 },
> +               .insize = sizeof(*resp),
> +       };
> +       int ret;
> +
> +       ret = cros_ec_cmd_xfer(ec, &msg);
> +       if (ret < 0)
> +               return ret;
> +
> +       if (msg.result != EC_RES_SUCCESS) {
> +               snprintf(str, maxlen,
> +                        "%s\nUnknown EC version: EC returned %d\n",
> +                        CROS_EC_DEV_VERSION, msg.result);
> +               return 0;
> +       }
> +
> +       resp = (struct ec_response_get_version *)msg.indata;
> +       if (resp->current_image >= ARRAY_SIZE(current_image_name))
> +               resp->current_image = 3; /* invalid */
> +
> +       snprintf(str, maxlen, "%s\n%s\n%s\n\%s\n", CROS_EC_DEV_VERSION,
> +                resp->version_string_ro, resp->version_string_rw,
> +                current_image_name[resp->current_image]);
> +
> +       return 0;
> +}
> +
> +/* Device file ops */
> +static int ec_device_open(struct inode *inode, struct file *filp)
> +{
> +       filp->private_data = container_of(inode->i_cdev,
> +                                         struct cros_ec_device, cdev);
> +       return 0;
> +}
> +
> +static int ec_device_release(struct inode *inode, struct file *filp)
> +{
> +       return 0;
> +}
> +
> +static ssize_t ec_device_read(struct file *filp, char __user *buffer,
> +                             size_t length, loff_t *offset)
> +{
> +       struct cros_ec_device *ec = filp->private_data;
> +       char msg[sizeof(struct ec_response_get_version) +
> +                sizeof(CROS_EC_DEV_VERSION)];
> +       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 ec_device_ioctl_xcmd(struct cros_ec_device *ec, void __user *arg)
> +{
> +       long ret;
> +       struct cros_ec_command s_cmd = { };
> +
> +       if (copy_from_user(&s_cmd, arg, sizeof(s_cmd)))
> +               return -EFAULT;
> +
> +       ret = cros_ec_cmd_xfer(ec, &s_cmd);
> +       /* Only copy data to userland if data was received. */
> +       if (ret < 0)
> +               return ret;
> +
> +       if (copy_to_user(arg, &s_cmd, sizeof(s_cmd)))
> +               return -EFAULT;
> +
> +       return 0;
> +}
> +
> +static long ec_device_ioctl_readmem(struct cros_ec_device *ec, void __user *arg)
> +{
> +       struct cros_ec_readmem s_mem = { };
> +       long num;
> +
> +       /* Not every platform supports direct reads */
> +       if (!ec->cmd_readmem)
> +               return -ENOTTY;
> +
> +       if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
> +               return -EFAULT;
> +
> +       num = ec->cmd_readmem(ec, 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 0;
> +}
> +
> +static long ec_device_ioctl(struct file *filp, unsigned int cmd,
> +                           unsigned long arg)
> +{
> +       struct cros_ec_device *ec = filp->private_data;
> +
> +       if (_IOC_TYPE(cmd) != CROS_EC_DEV_IOC)
> +               return -ENOTTY;
> +
> +       switch (cmd) {
> +       case CROS_EC_DEV_IOCXCMD:
> +               return ec_device_ioctl_xcmd(ec, (void __user *)arg);
> +       case CROS_EC_DEV_IOCRDMEM:
> +               return ec_device_ioctl_readmem(ec, (void __user *)arg);
> +       }
> +
> +       return -ENOTTY;
> +}
> +
> +/* Module initialization */
> +static const struct file_operations fops = {
> +       .open = ec_device_open,
> +       .release = ec_device_release,
> +       .read = ec_device_read,
> +       .unlocked_ioctl = ec_device_ioctl,
> +};
> +
> +static int ec_device_probe(struct platform_device *pdev)
> +{
> +       struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> +       int retval = -ENOTTY;
> +       dev_t devno = MKDEV(ec_major, 0);
> +
> +       /* Instantiate it (and remember the EC) */
> +       cdev_init(&ec->cdev, &fops);
> +
> +       retval = cdev_add(&ec->cdev, devno, 1);
> +       if (retval) {
> +               dev_err(&pdev->dev, ": failed to add character device\n");
> +               return retval;
> +       }
> +
> +       ec->vdev = device_create(cros_class, NULL, devno, ec,
> +                                CROS_EC_DEV_NAME);
> +       if (IS_ERR(ec->vdev)) {
> +               retval = PTR_ERR(ec->vdev);
> +               dev_err(&pdev->dev, ": failed to create device\n");
> +               cdev_del(&ec->cdev);
> +               return retval;
> +       }
> +
> +       return 0;
> +}
> +
> +static int ec_device_remove(struct platform_device *pdev)
> +{
> +       struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> +
> +       device_destroy(cros_class, MKDEV(ec_major, 0));
> +       cdev_del(&ec->cdev);
> +       return 0;
> +}
> +
> +static struct platform_driver cros_ec_dev_driver = {
> +       .driver = {
> +               .name = "cros-ec-dev",
> +       },
> +       .probe = ec_device_probe,
> +       .remove = ec_device_remove,
> +};
> +
> +static int __init cros_ec_dev_init(void)
> +{
> +       int ret;
> +       dev_t dev = 0;
> +
> +       cros_class = class_create(THIS_MODULE, "chromeos");
> +       if (IS_ERR(cros_class)) {
> +               pr_err(CROS_EC_DEV_NAME ": failed to register device class\n");
> +               return PTR_ERR(cros_class);
> +       }
> +
> +       /* Get a range of minor numbers (starting with 0) to work with */
> +       ret = alloc_chrdev_region(&dev, 0, CROS_MAX_DEV, CROS_EC_DEV_NAME);
> +       if (ret < 0) {
> +               pr_err(CROS_EC_DEV_NAME ": alloc_chrdev_region() failed\n");
> +               goto failed_chrdevreg;
> +       }
> +       ec_major = MAJOR(dev);
> +
> +       /* Register the driver */
> +       ret = platform_driver_register(&cros_ec_dev_driver);
> +       if (ret < 0) {
> +               pr_warn(CROS_EC_DEV_NAME ": can't register driver: %d\n", ret);
> +               goto failed_devreg;
> +       }
> +       return 0;
> +
> +failed_devreg:
> +       unregister_chrdev_region(MKDEV(ec_major, 0), CROS_MAX_DEV);
> +failed_chrdevreg:
> +       class_destroy(cros_class);
> +       return ret;
> +}
> +
> +static void __exit cros_ec_dev_exit(void)
> +{
> +       platform_driver_unregister(&cros_ec_dev_driver);
> +       unregister_chrdev(ec_major, CROS_EC_DEV_NAME);
> +       class_destroy(cros_class);
> +}
> +
> +module_init(cros_ec_dev_init);
> +module_exit(cros_ec_dev_exit);
> +
> +MODULE_AUTHOR("Bill Richardson <wfrichar@...omium.org>");
> +MODULE_DESCRIPTION("Userspace interface to the Chrome OS Embedded Controller");
> +MODULE_VERSION("1.0");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/platform/chrome/cros_ec_dev.h b/drivers/platform/chrome/cros_ec_dev.h
> new file mode 100644
> index 0000000..15c54c4
> --- /dev/null
> +++ b/drivers/platform/chrome/cros_ec_dev.h
> @@ -0,0 +1,47 @@
> +/*
> + * cros_ec_dev - expose the Chrome OS Embedded Controller to userspace
> + *
> + * 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_
> +
> +#include <linux/ioctl.h>
> +#include <linux/types.h>
> +#include <linux/mfd/cros_ec.h>
> +
> +#define CROS_EC_DEV_NAME "cros_ec"
> +#define CROS_EC_DEV_VERSION "1.0.0"
> +
> +/*
> + * @offset: within EC_LPC_ADDR_MEMMAP region
> + * @bytes: number of bytes to read. zero means "read a string" (including '\0')
> + *         (at most only EC_MEMMAP_SIZE bytes can be read)
> + * @buffer: where to store the result
> + * ioctl returns the number of bytes read, negative on error
> + */
> +struct cros_ec_readmem {
> +       uint32_t offset;
> +       uint32_t bytes;
> +       uint8_t buffer[EC_MEMMAP_SIZE];
> +};
> +
> +#define CROS_EC_DEV_IOC       0xEC
> +#define CROS_EC_DEV_IOCXCMD   _IOWR(CROS_EC_DEV_IOC, 0, struct cros_ec_command)
> +#define CROS_EC_DEV_IOCRDMEM  _IOWR(CROS_EC_DEV_IOC, 1, struct cros_ec_readmem)
> +
> +#endif /* _CROS_EC_DEV_H_ */
> --
> 2.1.3
>
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