[PATCH] i3c: add i3cdev module to expose i3c dev in /dev

[Vitor Soares]

This patch adds user mode support to I3C SDR transfers.

The module is based on spidev with the follow features:
  - Dynamically allocate the char device Major number.
  - Expose SDR (Single Data Rate) transfers

Signed-off-by: Vitor Soares <vitor.soares@xxxxxxxxxxxx>
---
 drivers/i3c/Kconfig             |  15 ++
 drivers/i3c/Makefile            |   1 +
 drivers/i3c/i3cdev.c            | 324 ++++++++++++++++++++++++++++++++
 include/uapi/linux/i3c/i3cdev.h |  38 ++++
 4 files changed, 378 insertions(+)
 create mode 100644 drivers/i3c/i3cdev.c
 create mode 100644 include/uapi/linux/i3c/i3cdev.h

diff --git a/drivers/i3c/Kconfig b/drivers/i3c/Kconfig
index 30a441506f61..01642768ab5f 100644
--- a/drivers/i3c/Kconfig
+++ b/drivers/i3c/Kconfig
@@ -20,5 +20,20 @@ menuconfig I3C
 	  will be called i3c.
 
 if I3C
+
+config I3CDEV
+	tristate "I3C device interface"
+	depends on I3C
+	help
+	  Say Y here to use i3c-* device files, usually found in the /dev
+	  directory on your system.  They make it possible to have user-space
+	  programs use the I3C devices.
+
+	  This support is also available as a module.  If so, the module
+	  will be called i3cdev.
+
+	  Note that this application programming interface is EXPERIMENTAL
+	  and hence SUBJECT TO CHANGE WITHOUT NOTICE while it stabilizes.
+
 source "drivers/i3c/master/Kconfig"
 endif # I3C
diff --git a/drivers/i3c/Makefile b/drivers/i3c/Makefile
index 11982efbc6d9..606d422841b2 100644
--- a/drivers/i3c/Makefile
+++ b/drivers/i3c/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 i3c-y				:= device.o master.o
 obj-$(CONFIG_I3C)		+= i3c.o
+obj-$(CONFIG_I3CDEV)		+= i3cdev.o
 obj-$(CONFIG_I3C)		+= master/
diff --git a/drivers/i3c/i3cdev.c b/drivers/i3c/i3cdev.c
new file mode 100644
index 000000000000..2b408a446ab6
--- /dev/null
+++ b/drivers/i3c/i3cdev.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2020 Synopsys, Inc. and/or its affiliates.
+ *
+ * Author: Vitor Soares <soares@xxxxxxxxxxxx>
+ */
+
+#include <linux/cdev.h>
+#include <linux/compat.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/i3c/device.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <uapi/linux/i3c/i3cdev.h>
+
+#define MAX_I3CDEV_DEVS (MINORMASK + 1)
+
+struct i3cdev_data {
+	struct i3c_device *i3c;
+	struct device *dev;
+	struct cdev cdev;
+	dev_t devt;
+};
+
+static DEFINE_IDA(i3cdev_ida);
+static dev_t i3cdev_first_chrdev;
+
+static ssize_t
+i3cdev_read(struct file *file, char __user *buf, size_t count, loff_t *f_pos)
+{
+	struct i3cdev_data *i3cdev = file->private_data;
+	struct i3c_device *i3c = i3cdev->i3c;
+	struct i3c_priv_xfer xfers = {
+		.rnw = true,
+		.len = count,
+	};
+	char *tmp;
+	int ret;
+
+	tmp = kzalloc(count, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	xfers.data.in = tmp;
+
+	dev_dbg(i3cdev->dev, "Reading %zu bytes.\n", count);
+
+	ret = i3c_device_do_priv_xfers(i3c, &xfers, 1);
+	if (!ret)
+		ret = copy_to_user(buf, tmp, xfers.len) ? -EFAULT : xfers.len;
+
+	kfree(tmp);
+	return ret;
+}
+
+static ssize_t
+i3cdev_write(struct file *file, const char __user *buf, size_t count,
+	     loff_t *f_pos)
+{
+	struct i3cdev_data *i3cdev = file->private_data;
+	struct i3c_device *i3c = i3cdev->i3c;
+	struct i3c_priv_xfer xfers = {
+		.rnw = false,
+		.len = count,
+	};
+	char *tmp;
+	int ret;
+
+	tmp = memdup_user(buf, count);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+
+	xfers.data.out = tmp;
+
+	dev_dbg(i3cdev->dev, "Writing %zu bytes.\n", count);
+
+	ret = i3c_device_do_priv_xfers(i3c, &xfers, 1);
+	kfree(tmp);
+
+	return !ret ? count : ret;
+}
+
+static int
+i3cdev_ioctl_priv_xfers(struct i3c_device *i3c,
+			struct i3cdev_priv_xfers __user *uxfers)
+{
+	struct i3cdev_priv_xfers xfers;
+	struct i3cdev_priv_xfer *uxfer_array;
+	struct i3c_priv_xfer *xfer_array;
+	unsigned int i;
+	int ret;
+
+	if (copy_from_user(&xfers, uxfers, sizeof(xfers)))
+		return -EFAULT;
+
+	/* TODO: Add a limit for xfers.nxfers. */
+	uxfer_array = memdup_user(u64_to_user_ptr(xfers.xfers),
+				  xfers.nxfers * sizeof(*uxfer_array));
+	if (!uxfer_array)
+		return -ENOMEM;
+
+	xfer_array = kmalloc_array(xfers.nxfers, sizeof(*xfer_array),
+				   GFP_KERNEL);
+	if (!xfer_array) {
+		ret = -ENOMEM;
+		goto out_free_uxfer_array;
+	}
+
+	/* TODO Add a limit for max in/out size. */
+	for (i = 0; i < xfers.nxfers; i++) {
+		void __user *udata = u64_to_user_ptr(uxfer_array[i].data);
+		void *data;
+
+		xfer_array[i].rnw = uxfer_array[i].rnw;
+		xfer_array[i].len = uxfer_array[i].len;
+
+		if (!xfer_array[i].rnw) {
+			data = memdup_user(udata, xfer_array[i].len);
+		} else {
+			data = kzalloc(xfer_array[i].len, GFP_KERNEL);
+			if (data)
+				data = ERR_PTR(-ENOMEM);
+		}
+
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(xfer_array[i].data.in);
+			goto out_free_xfer_array;
+		}
+
+		xfer_array[i].data.in = data;
+	}
+
+	ret = i3c_device_do_priv_xfers(i3c, xfer_array, xfers.nxfers);
+
+	if (!ret) {
+		for (i = 0; i < xfers.nxfers; i++) {
+			void __user *udata = u64_to_user_ptr(uxfer_array[i].data);
+			void *data = xfer_array[i].data.in;
+
+			if (!xfer_array[i].rnw)
+				continue;
+
+			if (copy_to_user(udata, data, xfer_array[i].len)) {
+				ret = -EFAULT;
+				goto out_free_xfer_array;
+			}
+		}
+	}
+
+out_free_xfer_array:
+	for (i = 0; i < xfers.nxfers; i++)
+		kfree(xfer_array[i].data.in);
+
+	kfree(xfer_array);
+
+out_free_uxfer_array:
+	kfree(uxfer_array);
+	return ret;
+}
+
+static long
+i3cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct i3cdev_data *i3cdev = file->private_data;
+	void __user *udata = (void __user *)arg;
+	int ret = -EACCES;
+
+	dev_dbg(i3cdev->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n", cmd, arg);
+
+	switch (cmd) {
+	case I3CDEV_PRIV_XFER:
+		ret = i3cdev_ioctl_priv_xfers(i3cdev->i3c, udata);
+		break;
+	default:
+		return -ENOTTY;
+	}
+
+	return ret;
+}
+
+static int i3cdev_open(struct inode *inode, struct file *file)
+{
+	struct i3cdev_data *i3cdev = container_of(inode->i_cdev,
+						  struct i3cdev_data,
+						  cdev);
+	file->private_data = i3cdev;
+
+	return 0;
+}
+
+static int i3cdev_release(struct inode *inode, struct file *file)
+{
+	file->private_data = NULL;
+
+	return 0;
+}
+
+static const struct file_operations i3cdev_fops = {
+	.owner = THIS_MODULE,
+	.read = i3cdev_read,
+	.write = i3cdev_write,
+	.unlocked_ioctl	= i3cdev_ioctl,
+	.compat_ioctl = compat_ptr_ioctl,
+	.open = i3cdev_open,
+	.release = i3cdev_release,
+};
+
+/* ------------------------------------------------------------------------- */
+
+static struct class *i3cdev_class;
+
+static int i3cdev_probe(struct i3c_device *i3c)
+{
+	struct device *dev = i3cdev_to_dev(i3c);
+	struct i3cdev_data *i3cdev;
+	int ret;
+	int id;
+
+	i3cdev = devm_kzalloc(dev, sizeof(*i3cdev), GFP_KERNEL);
+	if (!i3cdev)
+		return -ENOMEM;
+
+	ret = ida_simple_get(&i3cdev_ida, 0, MAX_I3CDEV_DEVS, GFP_KERNEL);
+	if (ret < 0) {
+		dev_err(dev, "no minor number available!\n");
+		return ret;
+	}
+
+	i3cdev->i3c = i3c;
+	i3cdev->devt = MKDEV(MAJOR(i3cdev_first_chrdev),
+			     MINOR(i3cdev_first_chrdev) + ret);
+	i3cdev_set_drvdata(i3c, i3cdev);
+	cdev_init(&i3cdev->cdev, &i3cdev_fops);
+	i3cdev->cdev.owner = THIS_MODULE;
+	ret = cdev_add(&i3cdev->cdev, i3cdev->devt, 1);
+	if (ret)
+		goto error_free_id;
+
+	i3cdev->dev = device_create(i3cdev_class, dev, i3cdev->devt,
+				    NULL, "i3cdev%d", id);
+	if (IS_ERR(i3cdev->dev)) {
+		ret = PTR_ERR(i3cdev->dev);
+		goto error_free_cdev;
+	}
+
+	return 0;
+
+error_free_cdev:
+	cdev_del(&i3cdev->cdev);
+error_free_id:
+	ida_free(&i3cdev_ida,
+		 MINOR(i3cdev->devt) - MINOR(i3cdev_first_chrdev));
+	return ret;
+}
+
+static int i3cdev_remove(struct i3c_device *i3c)
+{
+	struct i3cdev_data *i3cdev;
+
+	i3cdev = i3cdev_get_drvdata(i3c);
+
+	device_destroy(i3cdev_class, i3cdev->devt);
+	cdev_del(&i3cdev->cdev);
+	ida_simple_remove(&i3cdev_ida,
+			  MINOR(i3cdev->devt) - MINOR(i3cdev_first_chrdev));
+
+	return 0;
+}
+
+static const struct i3c_device_id i3cdev_ids[] = {
+	{ /* Sentinel */ },
+};
+
+static struct i3c_driver i3cdev_driver = {
+	.probe = i3cdev_probe,
+	.remove = i3cdev_remove,
+	.id_table = i3cdev_ids,
+};
+
+static int __init i3cdev_init(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&i3cdev_first_chrdev, 0, MAX_I3CDEV_DEVS,
+				  "i3cdev");
+	if (ret)
+		return ret;
+
+	i3cdev_class = class_create(THIS_MODULE, "i3cdev");
+	if (IS_ERR(i3cdev_class))
+		goto err_unreg_chrdev_region;
+
+	ret = i3c_driver_register(&i3cdev_driver);
+	if (ret)
+		goto err_destroy_class;
+
+	return 0;
+
+err_destroy_class:
+	class_destroy(i3cdev_class);
+err_unreg_chrdev_region:
+	unregister_chrdev_region(i3cdev_first_chrdev, MAX_I3CDEV_DEVS);
+	return ret;
+}
+module_init(i3cdev_init);
+
+static void __exit i3cdev_exit(void)
+{
+	i3c_driver_unregister(&i3cdev_driver);
+	class_destroy(i3cdev_class);
+	unregister_chrdev_region(i3cdev_first_chrdev, MAX_I3CDEV_DEVS);
+}
+module_exit(i3cdev_exit);
+
+MODULE_AUTHOR("Vitor Soares <soares@xxxxxxxxxxxx>");
+MODULE_DESCRIPTION("I3C /dev entries driver");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/i3c/i3cdev.h b/include/uapi/linux/i3c/i3cdev.h
new file mode 100644
index 000000000000..305dc029ca2d
--- /dev/null
+++ b/include/uapi/linux/i3c/i3cdev.h
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Copyright (c) 2020 Synopsys, Inc. and/or its affiliates.
+ *
+ * Author: Vitor Soares <vitor.soares@xxxxxxxxxxxx>
+ */
+
+#ifndef _UAPI_I3C_DEV_H_
+#define _UAPI_I3C_DEV_H_
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+/* IOCTL commands */
+#define I3C_DEV_IOC_MAGIC	0x07
+
+/**
+ * struct i3c_ioc_priv_xfer - I3C SDR ioctl private transfer
+ * @data: Holds pointer to userspace buffer with transmit data.
+ * @len: Length of data buffer buffers, in bytes.
+ * @rnw: encodes the transfer direction. true for a read, false for a write
+ */
+struct i3cdev_priv_xfer {
+	__u64 data;
+	__u16 len;
+	__u8 rnw;
+	__u8 pad[5];
+};
+
+struct i3cdev_priv_xfers {
+	__u64 nxfers;
+	__u64 xfers;
+};
+
+#define I3CDEV_PRIV_XFER \
+	_IOWR(I3C_DEV_IOC_MAGIC, 0, struct i3cdev_priv_xfers)
+
+#endif
-- 
2.24.1