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SubjectRe: [PATCH 03/10] mfd / platform: cros_ec: Miscellaneous character device to talk with the EC
Hi Greg,

Many thanks for your comments,

Missatge de Greg Kroah-Hartman <gregkh@linuxfoundation.org> del dia
dt., 4 de juny 2019 a les 17:53:
>
> On Tue, Jun 04, 2019 at 05:20:12PM +0200, Enric Balletbo i Serra 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@collabora.com>
> > ---
> >
> > Documentation/ioctl/ioctl-number.txt | 2 +-
> > drivers/mfd/cros_ec_dev.c | 2 +-
> > drivers/platform/chrome/Kconfig | 11 +
> > drivers/platform/chrome/Makefile | 1 +
> > drivers/platform/chrome/cros_ec_chardev.c | 279 ++++++++++++++++++
> > .../uapi/linux/cros_ec_chardev.h | 18 +-
> > 6 files changed, 302 insertions(+), 11 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 (70%)
> >
> > 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@de.ibm.com>
> > 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@winischhofer.net>
> > 0xF4 00-1F video/mbxfb.h mbxfb
> > diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> > index 607383b67cf1..11b791c28f84 100644
> > --- a/drivers/mfd/cros_ec_dev.c
> > +++ b/drivers/mfd/cros_ec_dev.c
> > @@ -15,7 +15,7 @@
> > #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 9417b982ad92..3a9ad001838a 100644
> > --- a/drivers/platform/chrome/Kconfig
> > +++ b/drivers/platform/chrome/Kconfig
> > @@ -147,6 +147,17 @@ 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 ebb57e21923b..d47a7e1097ee 100644
> > --- a/drivers/platform/chrome/Makefile
> > +++ b/drivers/platform/chrome/Makefile
> > @@ -16,6 +16,7 @@ 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..1a0a27080026
> > --- /dev/null
> > +++ b/drivers/platform/chrome/cros_ec_chardev.c
> > @@ -0,0 +1,279 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Miscellaneous character driver for ChromeOS Embedded Controller
> > + *
> > + * Copyright 2019 Google LLC
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/device.h>
> > +#include <linux/fs.h>
> > +#include <linux/list.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/spinlock.h>
> > +#include <linux/types.h>
> > +#include <linux/uaccess.h>
> > +
> > +#include <uapi/linux/cros_ec_chardev.h>
> > +
> > +#define DRV_NAME "cros-ec-chardev"
> > +
> > +static LIST_HEAD(chardev_devices);
> > +static DEFINE_SPINLOCK(chardev_lock);
> > +
> > +struct chardev_data {
> > + struct list_head list;
> > + 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",
> > + 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;
> > + int ret;
> > +
> > + /* 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;
> > +
> > + ret = misc_register(&data->misc);
> > + if (ret)
> > + return ret;
> > +
> > + spin_lock(&chardev_lock);
> > + list_add(&data->list, &chardev_devices);
> > + spin_unlock(&chardev_lock);
> > +
> > + dev_info(&pdev->dev, "Created misc device /dev/%s\n",
> > + data->misc.name);
>
> No need to be noisy, if all goes well, your code should be quiet.

Ok, I'll remove on next version.

> > +
> > + return 0;
> > +}
> > +
> > +static int cros_ec_chardev_remove(struct platform_device *pdev)
> > +{
> > + struct cros_ec_dev *ec_dev = dev_get_drvdata(pdev->dev.parent);
> > + struct chardev_data *data;
> > +
> > + list_for_each_entry(data, &chardev_devices, list)
> > + if (data->ec_dev == ec_dev)
> > + break;
> > +
> > + if (data->ec_dev != ec_dev) {
> > + dev_err(&pdev->dev,
> > + "remove called but miscdevice %s not found\n",
> > + data->misc.name);
> > + return -ENODEV;
> > + }
>
> Why do you have this separate list of devices? You don't seem to need
> it, you only iterate over it, why is it needed?
>

Right, my bad, I was carrying some code from an old version that is
not needed at all now. I'll remove all the related code.

> > + spin_lock(&chardev_lock);
> > + list_del(&data->list);
> > + spin_unlock(&chardev_lock);
> > + misc_deregister(&data->misc);
> > +
> > + return 0;
> > +}
>
> You also iterate over the list without the lock, so why even have the
> lock? Are you sure the list, and the lock, is even needed?
>

Right, not needed. Removed on next version.

Thanks,
Enric

> thanks,
>
> greg k-h

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