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

[Enric Balletbo i Serra]

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>
---

 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@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 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);
+
+	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;
+	}
+
+	spin_lock(&chardev_lock);
+	list_del(&data->list);
+	spin_unlock(&chardev_lock);
+	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 70%
rename from drivers/mfd/cros_ec_dev.h
rename to include/uapi/linux/cros_ec_chardev.h
index 7a42c3ef50e4..c6dd2549a2a5 100644
--- a/drivers/mfd/cros_ec_dev.h
+++ b/include/uapi/linux/cros_ec_chardev.h
@@ -1,12 +1,12 @@
-/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* 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.
  */
 
-#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>
@@ -20,16 +20,16 @@
  * @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. The ioctl returns the number of bytes
- *         read or negative on error.
+ *          read or negative on error.
  */
 struct cros_ec_readmem {
-	uint32_t offset;
-	uint32_t bytes;
-	uint8_t buffer[EC_MEMMAP_SIZE];
+	__u32	offset;
+	__u32	bytes;
+	__u8	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_ */
+#endif /* _UAPI_LINUX_CROS_EC_DEV_H_ */
-- 
2.20.1