char: vcio: Rewrite as a firmware node child

The old vcio driver is a simple character device that manually locates
the firmware driver. Initialising it before the firmware driver causes
a failure, and no retries are attempted.

Rewrite vcio as a platform driver that depends on a DT node for its
instantiation and the location of the firmware driver, making use of
the miscdevice framework to reduce the code size.

N.B. Using miscdevice changes the udev SUBSYSTEM string, so a change
to the companion udev rule is required in order to continue to set
the correct device permissions, e.g.:

    KERNEL="vcio", GROUP="video", MODE="0660"

See: #4620

Signed-off-by: Phil Elwell <[email protected]>

Author: pelwell

drivers/char/broadcom/vcio.c

@@ -1,15 +1,14 @@
 /*
  *  Copyright (C) 2010 Broadcom
  *  Copyright (C) 2015 Noralf Trønnes
+ *  Copyright (C) 2021 Raspberry Pi (Trading) Ltd.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
  */
 
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
 #include <linux/cdev.h>
 #include <linux/device.h>
 #include <linux/fs.h>
@@ -19,24 +18,22 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/compat.h>
+#include <linux/miscdevice.h>
 #include <soc/bcm2835/raspberrypi-firmware.h>
 
-#define MBOX_CHAN_PROPERTY 8
-
+#define MODULE_NAME "vcio"
 #define VCIO_IOC_MAGIC 100
 #define IOCTL_MBOX_PROPERTY _IOWR(VCIO_IOC_MAGIC, 0, char *)
 #ifdef CONFIG_COMPAT
 #define IOCTL_MBOX_PROPERTY32 _IOWR(VCIO_IOC_MAGIC, 0, compat_uptr_t)
 #endif
 
-static struct {
-	dev_t devt;
-	struct cdev cdev;
-	struct class *class;
+struct vcio_data {
 	struct rpi_firmware *fw;
-} vcio;
+	struct miscdevice misc_dev;
+};
 
-static int vcio_user_property_list(void *user)
+static int vcio_user_property_list(struct vcio_data *vcio, void *user)
 {
 	u32 *buf, size;
 	int ret;
@@ -55,7 +52,7 @@ static int vcio_user_property_list(void *user)
 	}
 
 	/* Strip off protocol encapsulation */
-	ret = rpi_firmware_property_list(vcio.fw, &buf[2], size - 12);
+	ret = rpi_firmware_property_list(vcio->fw, &buf[2], size - 12);
 	if (ret) {
 		kfree(buf);
 		return ret;
@@ -87,9 +84,12 @@ static int vcio_device_release(struct inode *inode, struct file *file)
 static long vcio_device_ioctl(struct file *file, unsigned int ioctl_num,
 			      unsigned long ioctl_param)
 {
+	struct vcio_data *vcio = container_of(file->private_data,
+					      struct vcio_data, misc_dev);
+
 	switch (ioctl_num) {
 	case IOCTL_MBOX_PROPERTY:
-		return vcio_user_property_list((void *)ioctl_param);
+		return vcio_user_property_list(vcio, (void *)ioctl_param);
 	default:
 		pr_err("unknown ioctl: %x\n", ioctl_num);
 		return -EINVAL;
@@ -100,9 +100,12 @@ static long vcio_device_ioctl(struct file *file, unsigned int ioctl_num,
 static long vcio_device_compat_ioctl(struct file *file, unsigned int ioctl_num,
 				     unsigned long ioctl_param)
 {
+	struct vcio_data *vcio = container_of(file->private_data,
+					      struct vcio_data, misc_dev);
+
 	switch (ioctl_num) {
 	case IOCTL_MBOX_PROPERTY32:
-		return vcio_user_property_list(compat_ptr(ioctl_param));
+		return vcio_user_property_list(vcio, compat_ptr(ioctl_param));
 	default:
 		pr_err("unknown ioctl: %x\n", ioctl_num);
 		return -EINVAL;
@@ -119,77 +122,65 @@ const struct file_operations vcio_fops = {
 	.release = vcio_device_release,
 };
 
-static int __init vcio_init(void)
+static int vcio_probe(struct platform_device *pdev)
 {
-	struct device_node *np;
-	static struct device *dev;
-	int ret;
-
-	np = of_find_compatible_node(NULL, NULL,
-				     "raspberrypi,bcm2835-firmware");
-	if (!of_device_is_available(np))
-		return -ENODEV;
-
-	vcio.fw = rpi_firmware_get(np);
-	if (!vcio.fw)
-		return -ENODEV;
-
-	ret = alloc_chrdev_region(&vcio.devt, 0, 1, "vcio");
-	if (ret) {
-		pr_err("failed to allocate device number\n");
-		return ret;
-	}
-
-	cdev_init(&vcio.cdev, &vcio_fops);
-	vcio.cdev.owner = THIS_MODULE;
-	ret = cdev_add(&vcio.cdev, vcio.devt, 1);
-	if (ret) {
-		pr_err("failed to register device\n");
-		goto err_unregister_chardev;
-	}
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *fw_node;
+	struct rpi_firmware *fw;
+	struct vcio_data *vcio;
 
-	/*
-	 * Create sysfs entries
-	 * 'bcm2708_vcio' is used for backwards compatibility so we don't break
-	 * userspace. Raspian has a udev rule that changes the permissions.
-	 */
-	vcio.class = class_create(THIS_MODULE, "bcm2708_vcio");
-	if (IS_ERR(vcio.class)) {
-		ret = PTR_ERR(vcio.class);
-		pr_err("failed to create class\n");
-		goto err_cdev_del;
+	fw_node = of_get_parent(np);
+	if (!fw_node) {
+		dev_err(dev, "Missing firmware node\n");
+		return -ENOENT;
 	}
 
-	dev = device_create(vcio.class, NULL, vcio.devt, NULL, "vcio");
-	if (IS_ERR(dev)) {
-		ret = PTR_ERR(dev);
-		pr_err("failed to create device\n");
-		goto err_class_destroy;
-	}
+	fw = rpi_firmware_get(fw_node);
+	of_node_put(fw_node);
+	if (!fw)
+		return -EPROBE_DEFER;
 
-	return 0;
+	vcio = devm_kzalloc(dev, sizeof(struct vcio_data), GFP_KERNEL);
+	if (!vcio)
+		return -ENOMEM;
 
-err_class_destroy:
-	class_destroy(vcio.class);
-err_cdev_del:
-	cdev_del(&vcio.cdev);
-err_unregister_chardev:
-	unregister_chrdev_region(vcio.devt, 1);
+	vcio->fw = fw;
+	vcio->misc_dev.fops = &vcio_fops;
+	vcio->misc_dev.minor = MISC_DYNAMIC_MINOR;
+	vcio->misc_dev.name = "vcio";
+	vcio->misc_dev.parent = dev;
 
-	return ret;
+	return misc_register(&vcio->misc_dev);
 }
-module_init(vcio_init);
 
-static void __exit vcio_exit(void)
+static int vcio_remove(struct platform_device *pdev)
 {
-	device_destroy(vcio.class, vcio.devt);
-	class_destroy(vcio.class);
-	cdev_del(&vcio.cdev);
-	unregister_chrdev_region(vcio.devt, 1);
+	struct device *dev = &pdev->dev;
+
+	misc_deregister(dev_get_drvdata(dev));
+	return 0;
 }
-module_exit(vcio_exit);
+
+static const struct of_device_id vcio_ids[] = {
+	{ .compatible = "raspberrypi,vcio" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, vcio_ids);
+
+static struct platform_driver vcio_driver = {
+	.driver	= {
+		.name		= MODULE_NAME,
+		.of_match_table	= of_match_ptr(vcio_ids),
+	},
+	.probe	= vcio_probe,
+	.remove = vcio_remove,
+};
+
+module_platform_driver(vcio_driver);
 
 MODULE_AUTHOR("Gray Girling");
 MODULE_AUTHOR("Noralf Trønnes");
 MODULE_DESCRIPTION("Mailbox userspace access");
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:rpi-vcio");