sh: Add maple bus support for the SEGA Dreamcast.

The Maple bus is SEGA's proprietary serial bus for peripherals
(keyboard, mouse, controller etc). The bus is capable of some
(limited) hotplugging and operates at up to 2 M/bits.

Drivers of one sort or another existed/exist for 2.4 and a rudimentary
port, which didn't support the 2.6 device driver model was also in
existence.

This driver - for the bus logic itself and for the keyboard (other
drivers will follow) are based on the code and concepts of those old
drivers but have lots of completely rewritten parts.

I have the maple bus code as a built in now as that seems the sane and
rational way to handle something like that - you either want the bus
or you don't.

Signed-off-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

2 files changed, 738 insertions, 0 deletions

diff --git a/drivers/sh/maple/Makefile b/drivers/sh/maple/Makefile
new file mode 100644
index 000000000000..65dfeeb610ef
--- /dev/null
+++ b/drivers/sh/maple/Makefile
@@ -0,0 +1,3 @@
+# Makefile for Maple Bus
+
+obj-$(CONFIG_MAPLE) := maple.o
diff --git a/drivers/sh/maple/maple.c b/drivers/sh/maple/maple.c
new file mode 100644
index 000000000000..161d1021b7eb
--- /dev/null
+++ b/drivers/sh/maple/maple.c
@@ -0,0 +1,735 @@
+/*
+ * Core maple bus functionality
+ *
+ *  Copyright (C) 2007 Adrian McMenamin
+ *
+ * Based on 2.4 code by:
+ *
+ *  Copyright (C) 2000-2001 YAEGASHI Takeshi
+ *  Copyright (C) 2001 M. R. Brown
+ *  Copyright (C) 2001 Paul Mundt
+ *
+ * and others.
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/maple.h>
+#include <linux/dma-mapping.h>
+#include <asm/cacheflush.h>
+#include <asm/dma.h>
+#include <asm/io.h>
+#include <asm/mach/dma.h>
+#include <asm/mach/sysasic.h>
+#include <asm/mach/maple.h>
+
+MODULE_AUTHOR("Yaegshi Takeshi, Paul Mundt, M.R. Brown, Adrian McMenamin");
+MODULE_DESCRIPTION("Maple bus driver for Dreamcast");
+MODULE_LICENSE("GPL v2");
+MODULE_SUPPORTED_DEVICE("{{SEGA, Dreamcast/Maple}}");
+
+static void maple_dma_handler(struct work_struct *work);
+static void maple_vblank_handler(struct work_struct *work);
+
+static DECLARE_WORK(maple_dma_process, maple_dma_handler);
+static DECLARE_WORK(maple_vblank_process, maple_vblank_handler);
+
+static LIST_HEAD(maple_waitq);
+static LIST_HEAD(maple_sentq);
+
+static DEFINE_MUTEX(maple_list_lock);
+
+static struct maple_driver maple_dummy_driver;
+static struct device maple_bus;
+static int subdevice_map[MAPLE_PORTS];
+static unsigned long *maple_sendbuf, *maple_sendptr, *maple_lastptr;
+static unsigned long maple_pnp_time;
+static int started, scanning, liststatus;
+static struct kmem_cache *maple_queue_cache;
+
+struct maple_device_specify {
+       int port;
+       int unit;
+};
+
+/**
+ *  maple_driver_register - register a device driver
+ *  automatically makes the driver bus a maple bus
+ *  @drv: the driver to be registered
+ */
+int maple_driver_register(struct device_driver *drv)
+{
+       if (!drv)
+               return -EINVAL;
+       drv->bus = &maple_bus_type;
+       return driver_register(drv);
+}
+EXPORT_SYMBOL_GPL(maple_driver_register);
+
+/* set hardware registers to enable next round of dma */
+static void maplebus_dma_reset(void)
+{
+       ctrl_outl(MAPLE_MAGIC, MAPLE_RESET);
+       /* set trig type to 0 for software trigger, 1 for hardware (VBLANK) */
+       ctrl_outl(1, MAPLE_TRIGTYPE);
+       ctrl_outl(MAPLE_2MBPS | MAPLE_TIMEOUT(50000), MAPLE_SPEED);
+       ctrl_outl(PHYSADDR(maple_sendbuf), MAPLE_DMAADDR);
+       ctrl_outl(1, MAPLE_ENABLE);
+}
+
+/**
+ * maple_getcond_callback - setup handling MAPLE_COMMAND_GETCOND
+ * @dev: device responding
+ * @callback: handler callback
+ * @interval: interval in jiffies between callbacks
+ * @function: the function code for the device
+ */
+void maple_getcond_callback(struct maple_device *dev,
+                           void (*callback) (struct mapleq * mq),
+                           unsigned long interval, unsigned long function)
+{
+       dev->callback = callback;
+       dev->interval = interval;
+       dev->function = cpu_to_be32(function);
+       dev->when = jiffies;
+}
+EXPORT_SYMBOL_GPL(maple_getcond_callback);
+
+static int maple_dma_done(void)
+{
+       return (ctrl_inl(MAPLE_STATE) & 1) == 0;
+}
+
+static void maple_release_device(struct device *dev)
+{
+       if (dev->type) {
+               kfree(dev->type->name);
+               kfree(dev->type);
+       }
+}
+
+/**
+ * maple_add_packet - add a single instruction to the queue
+ * @mq: instruction to add to waiting queue
+ */
+void maple_add_packet(struct mapleq *mq)
+{
+       mutex_lock(&maple_list_lock);
+       list_add(&mq->list, &maple_waitq);
+       mutex_unlock(&maple_list_lock);
+}
+EXPORT_SYMBOL_GPL(maple_add_packet);
+
+static struct mapleq *maple_allocq(struct maple_device *dev)
+{
+       struct mapleq *mq;
+
+       mq = kmalloc(sizeof(*mq), GFP_KERNEL);
+       if (!mq)
+               return NULL;
+
+       mq->dev = dev;
+       mq->recvbufdcsp = kmem_cache_zalloc(maple_queue_cache, GFP_KERNEL);
+       mq->recvbuf = (void *) P2SEGADDR(mq->recvbufdcsp);
+       if (!mq->recvbuf) {
+               kfree(mq);
+               return NULL;
+       }
+
+       return mq;
+}
+
+static struct maple_device *maple_alloc_dev(int port, int unit)
+{
+       struct maple_device *dev;
+
+       dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+       if (!dev)
+               return NULL;
+
+       dev->port = port;
+       dev->unit = unit;
+       dev->mq = maple_allocq(dev);
+
+       if (!dev->mq) {
+               kfree(dev);
+               return NULL;
+       }
+
+       return dev;
+}
+
+static void maple_free_dev(struct maple_device *mdev)
+{
+       if (!mdev)
+               return;
+       if (mdev->mq) {
+               kmem_cache_free(maple_queue_cache, mdev->mq->recvbufdcsp);
+               kfree(mdev->mq);
+       }
+       kfree(mdev);
+}
+
+/* process the command queue into a maple command block
+ * terminating command has bit 32 of first long set to 0
+ */
+static void maple_build_block(struct mapleq *mq)
+{
+       int port, unit, from, to, len;
+       unsigned long *lsendbuf = mq->sendbuf;
+
+       port = mq->dev->port & 3;
+       unit = mq->dev->unit;
+       len = mq->length;
+       from = port << 6;
+       to = (port << 6) | (unit > 0 ? (1 << (unit - 1)) & 0x1f : 0x20);
+
+       *maple_lastptr &= 0x7fffffff;
+       maple_lastptr = maple_sendptr;
+
+       *maple_sendptr++ = (port << 16) | len | 0x80000000;
+       *maple_sendptr++ = PHYSADDR(mq->recvbuf);
+       *maple_sendptr++ =
+           mq->command | (to << 8) | (from << 16) | (len << 24);
+
+       while (len-- > 0)
+               *maple_sendptr++ = *lsendbuf++;
+}
+
+/* build up command queue */
+static void maple_send(void)
+{
+       int i;
+       int maple_packets;
+       struct mapleq *mq, *nmq;
+
+       if (!list_empty(&maple_sentq))
+               return;
+       if (list_empty(&maple_waitq) || !maple_dma_done())
+               return;
+       maple_packets = 0;
+       maple_sendptr = maple_lastptr = maple_sendbuf;
+       list_for_each_entry_safe(mq, nmq, &maple_waitq, list) {
+               maple_build_block(mq);
+               list_move(&mq->list, &maple_sentq);
+               if (maple_packets++ > MAPLE_MAXPACKETS)
+                       break;
+       }
+       if (maple_packets > 0) {
+               for (i = 0; i < (1 << MAPLE_DMA_PAGES); i++)
+                       dma_cache_sync(0, maple_sendbuf + i * PAGE_SIZE,
+                                      PAGE_SIZE, DMA_BIDIRECTIONAL);
+       }
+}
+
+static int attach_matching_maple_driver(struct device_driver *driver,
+                                       void *devptr)
+{
+       struct maple_driver *maple_drv;
+       struct maple_device *mdev;
+
+       mdev = devptr;
+       maple_drv = to_maple_driver(driver);
+       if (mdev->devinfo.function & be32_to_cpu(maple_drv->function)) {
+               if (maple_drv->connect(mdev) == 0) {
+                       mdev->driver = maple_drv;
+                       return 1;
+               }
+       }
+       return 0;
+}
+
+static void maple_detach_driver(struct maple_device *mdev)
+{
+       if (!mdev)
+               return;
+       if (mdev->driver) {
+               if (mdev->driver->disconnect)
+                       mdev->driver->disconnect(mdev);
+       }
+       mdev->driver = NULL;
+       if (mdev->registered) {
+               maple_release_device(&mdev->dev);
+               device_unregister(&mdev->dev);
+       }
+       mdev->registered = 0;
+       maple_free_dev(mdev);
+}
+
+/* process initial MAPLE_COMMAND_DEVINFO for each device or port */
+static void maple_attach_driver(struct maple_device *dev)
+{
+       char *p;
+
+       char *recvbuf;
+       unsigned long function;
+       int matched, retval;
+
+       recvbuf = dev->mq->recvbuf;
+       memcpy(&dev->devinfo, recvbuf + 4, sizeof(dev->devinfo));
+       memcpy(dev->product_name, dev->devinfo.product_name, 30);
+       memcpy(dev->product_licence, dev->devinfo.product_licence, 60);
+       dev->product_name[30] = '\0';
+       dev->product_licence[60] = '\0';
+
+       for (p = dev->product_name + 29; dev->product_name <= p; p--)
+               if (*p == ' ')
+                       *p = '\0';
+               else
+                       break;
+
+       for (p = dev->product_licence + 59; dev->product_licence <= p; p--)
+               if (*p == ' ')
+                       *p = '\0';
+               else
+                       break;
+
+       function = be32_to_cpu(dev->devinfo.function);
+
+       if (function > 0x200) {
+               /* Do this silently - as not a real device */
+               function = 0;
+               dev->driver = &maple_dummy_driver;
+               sprintf(dev->dev.bus_id, "%d:0.port", dev->port);
+       } else {
+               printk(KERN_INFO
+                      "Maple bus at (%d, %d): Connected function 0x%lX\n",
+                      dev->port, dev->unit, function);
+
+               matched =
+                   bus_for_each_drv(&maple_bus_type, NULL, dev,
+                                    attach_matching_maple_driver);
+
+               if (matched == 0) {
+                       /* Driver does not exist yet */
+                       printk(KERN_INFO
+                              "No maple driver found for this device\n");
+                       dev->driver = &maple_dummy_driver;
+               }
+
+               sprintf(dev->dev.bus_id, "%d:0%d.%lX", dev->port,
+                       dev->unit, function);
+       }
+       dev->function = function;
+       dev->dev.bus = &maple_bus_type;
+       dev->dev.parent = &maple_bus;
+       dev->dev.release = &maple_release_device;
+       retval = device_register(&dev->dev);
+       if (retval) {
+               printk(KERN_INFO
+                      "Maple bus: Attempt to register device (%x, %x) failed.\n",
+                      dev->port, dev->unit);
+               maple_free_dev(dev);
+       }
+       dev->registered = 1;
+}
+
+/*
+ * if device has been registered for the given
+ * port and unit then return 1 - allows identification
+ * of which devices need to be attached or detached
+ */
+static int detach_maple_device(struct device *device, void *portptr)
+{
+       struct maple_device_specify *ds;
+       struct maple_device *mdev;
+
+       ds = portptr;
+       mdev = to_maple_dev(device);
+       if (mdev->port == ds->port && mdev->unit == ds->unit)
+               return 1;
+       return 0;
+}
+
+static int setup_maple_commands(struct device *device, void *ignored)
+{
+       struct maple_device *maple_dev = to_maple_dev(device);
+
+       if ((maple_dev->interval > 0)
+           && time_after(jiffies, maple_dev->when)) {
+               maple_dev->when = jiffies + maple_dev->interval;
+               maple_dev->mq->command = MAPLE_COMMAND_GETCOND;
+               maple_dev->mq->sendbuf = &maple_dev->function;
+               maple_dev->mq->length = 1;
+               maple_add_packet(maple_dev->mq);
+               liststatus++;
+       } else {
+               if (time_after(jiffies, maple_pnp_time)) {
+                       maple_dev->mq->command = MAPLE_COMMAND_DEVINFO;
+                       maple_dev->mq->length = 0;
+                       maple_add_packet(maple_dev->mq);
+                       liststatus++;
+               }
+       }
+
+       return 0;
+}
+
+/* VBLANK bottom half - implemented via workqueue */
+static void maple_vblank_handler(struct work_struct *work)
+{
+       if (!maple_dma_done())
+               return;
+       if (!list_empty(&maple_sentq))
+               return;
+       ctrl_outl(0, MAPLE_ENABLE);
+       liststatus = 0;
+       bus_for_each_dev(&maple_bus_type, NULL, NULL,
+                        setup_maple_commands);
+       if (time_after(jiffies, maple_pnp_time))
+               maple_pnp_time = jiffies + MAPLE_PNP_INTERVAL;
+       if (liststatus && list_empty(&maple_sentq)) {
+               INIT_LIST_HEAD(&maple_sentq);
+               maple_send();
+       }
+       maplebus_dma_reset();
+}
+
+/* handle devices added via hotplugs - placing them on queue for DEVINFO*/
+static void maple_map_subunits(struct maple_device *mdev, int submask)
+{
+       int retval, k, devcheck;
+       struct maple_device *mdev_add;
+       struct maple_device_specify ds;
+
+       for (k = 0; k < 5; k++) {
+               ds.port = mdev->port;
+               ds.unit = k + 1;
+               retval =
+                   bus_for_each_dev(&maple_bus_type, NULL, &ds,
+                                    detach_maple_device);
+               if (retval) {
+                       submask = submask >> 1;
+                       continue;
+               }
+               devcheck = submask & 0x01;
+               if (devcheck) {
+                       mdev_add = maple_alloc_dev(mdev->port, k + 1);
+                       if (!mdev_add)
+                               return;
+                       mdev_add->mq->command = MAPLE_COMMAND_DEVINFO;
+                       mdev_add->mq->length = 0;
+                       maple_add_packet(mdev_add->mq);
+                       scanning = 1;
+               }
+               submask = submask >> 1;
+       }
+}
+
+/* mark a device as removed */
+static void maple_clean_submap(struct maple_device *mdev)
+{
+       int killbit;
+
+       killbit = (mdev->unit > 0 ? (1 << (mdev->unit - 1)) & 0x1f : 0x20);
+       killbit = ~killbit;
+       killbit &= 0xFF;
+       subdevice_map[mdev->port] = subdevice_map[mdev->port] & killbit;
+}
+
+/* handle empty port or hotplug removal */
+static void maple_response_none(struct maple_device *mdev,
+                               struct mapleq *mq)
+{
+       if (mdev->unit != 0) {
+               list_del(&mq->list);
+               maple_clean_submap(mdev);
+               printk(KERN_INFO
+                      "Maple bus device detaching at (%d, %d)\n",
+                      mdev->port, mdev->unit);
+               maple_detach_driver(mdev);
+               return;
+       }
+       if (!started) {
+               printk(KERN_INFO "No maple devices attached to port %d\n",
+                      mdev->port);
+               return;
+       }
+       maple_clean_submap(mdev);
+}
+
+/* preprocess hotplugs or scans */
+static void maple_response_devinfo(struct maple_device *mdev,
+                                  char *recvbuf)
+{
+       char submask;
+       if ((!started) || (scanning == 2)) {
+               maple_attach_driver(mdev);
+               return;
+       }
+       if (mdev->unit == 0) {
+               submask = recvbuf[2] & 0x1F;
+               if (submask ^ subdevice_map[mdev->port]) {
+                       maple_map_subunits(mdev, submask);
+                       subdevice_map[mdev->port] = submask;
+               }
+       }
+}
+
+/* maple dma end bottom half - implemented via workqueue */
+static void maple_dma_handler(struct work_struct *work)
+{
+       struct mapleq *mq, *nmq;
+       struct maple_device *dev;
+       char *recvbuf;
+       enum maple_code code;
+
+       if (!maple_dma_done())
+               return;
+       ctrl_outl(0, MAPLE_ENABLE);
+       if (!list_empty(&maple_sentq)) {
+               list_for_each_entry_safe(mq, nmq, &maple_sentq, list) {
+                       recvbuf = mq->recvbuf;
+                       code = recvbuf[0];
+                       dev = mq->dev;
+                       switch (code) {
+                       case MAPLE_RESPONSE_NONE:
+                               maple_response_none(dev, mq);
+                               break;
+
+                       case MAPLE_RESPONSE_DEVINFO:
+                               maple_response_devinfo(dev, recvbuf);
+                               break;
+
+                       case MAPLE_RESPONSE_DATATRF:
+                               if (dev->callback)
+                                       dev->callback(mq);
+                               break;
+
+                       case MAPLE_RESPONSE_FILEERR:
+                       case MAPLE_RESPONSE_AGAIN:
+                       case MAPLE_RESPONSE_BADCMD:
+                       case MAPLE_RESPONSE_BADFUNC:
+                               printk(KERN_DEBUG
+                                      "Maple non-fatal error 0x%X\n",
+                                      code);
+                               break;
+
+                       case MAPLE_RESPONSE_ALLINFO:
+                               printk(KERN_DEBUG
+                                      "Maple - extended device information not supported\n");
+                               break;
+
+                       case MAPLE_RESPONSE_OK:
+                               break;
+
+                       default:
+                               break;
+                       }
+               }
+               INIT_LIST_HEAD(&maple_sentq);
+               if (scanning == 1) {
+                       maple_send();
+                       scanning = 2;
+               } else
+                       scanning = 0;
+
+               if (started == 0)
+                       started = 1;
+       }
+       maplebus_dma_reset();
+}
+
+static irqreturn_t maplebus_dma_interrupt(int irq, void *dev_id)
+{
+       /* Load everything into the bottom half */
+       schedule_work(&maple_dma_process);
+       return IRQ_HANDLED;
+}
+
+static irqreturn_t maplebus_vblank_interrupt(int irq, void *dev_id)
+{
+       schedule_work(&maple_vblank_process);
+       return IRQ_HANDLED;
+}
+
+static struct irqaction maple_dma_irq = {
+       .name = "maple bus DMA handler",
+       .handler = maplebus_dma_interrupt,
+       .flags = IRQF_SHARED,
+};
+
+static struct irqaction maple_vblank_irq = {
+       .name = "maple bus VBLANK handler",
+       .handler = maplebus_vblank_interrupt,
+       .flags = IRQF_SHARED,
+};
+
+static int maple_set_dma_interrupt_handler(void)
+{
+       return setup_irq(HW_EVENT_MAPLE_DMA, &maple_dma_irq);
+}
+
+static int maple_set_vblank_interrupt_handler(void)
+{
+       return setup_irq(HW_EVENT_VSYNC, &maple_vblank_irq);
+}
+
+static int maple_get_dma_buffer(void)
+{
+       maple_sendbuf =
+           (void *) __get_free_pages(GFP_KERNEL | __GFP_ZERO,
+                                     MAPLE_DMA_PAGES);
+       if (!maple_sendbuf)
+               return -ENOMEM;
+       return 0;
+}
+
+static int match_maple_bus_driver(struct device *devptr,
+                                 struct device_driver *drvptr)
+{
+       struct maple_driver *maple_drv;
+       struct maple_device *maple_dev;
+
+       maple_drv = container_of(drvptr, struct maple_driver, drv);
+       maple_dev = container_of(devptr, struct maple_device, dev);
+       /* Trap empty port case */
+       if (maple_dev->devinfo.function == 0xFFFFFFFF)
+               return 0;
+       else if (maple_dev->devinfo.function &
+                be32_to_cpu(maple_drv->function))
+               return 1;
+       return 0;
+}
+
+static int maple_bus_uevent(struct device *dev, char **envp,
+                           int num_envp, char *buffer, int buffer_size)
+{
+       return 0;
+}
+
+static void maple_bus_release(struct device *dev)
+{
+}
+
+static struct maple_driver maple_dummy_driver = {
+       .drv = {
+               .name = "maple_dummy_driver",
+               .bus =  &maple_bus_type,
+       },
+};
+
+struct bus_type maple_bus_type = {
+       .name =         "maple",
+       .match =        match_maple_bus_driver,
+       .uevent =       maple_bus_uevent,
+};
+EXPORT_SYMBOL_GPL(maple_bus_type);
+
+static struct device maple_bus = {
+       .bus_id = "maple",
+       .release = maple_bus_release,
+};
+
+static int __init maple_bus_init(void)
+{
+       int retval, i;
+       struct maple_device *mdev[MAPLE_PORTS];
+       ctrl_outl(0, MAPLE_STATE);
+
+       retval = device_register(&maple_bus);
+       if (retval)
+               goto cleanup;
+
+       retval = bus_register(&maple_bus_type);
+       if (retval)
+               goto cleanup_device;
+
+       retval = driver_register(&maple_dummy_driver.drv);
+
+       if (retval)
+               goto cleanup_bus;
+
+       /* allocate memory for maple bus dma */
+       retval = maple_get_dma_buffer();
+       if (retval) {
+               printk(KERN_INFO
+                      "Maple bus: Failed to allocate Maple DMA buffers\n");
+               goto cleanup_basic;
+       }
+
+       /* set up DMA interrupt handler */
+       retval = maple_set_dma_interrupt_handler();
+       if (retval) {
+               printk(KERN_INFO
+                      "Maple bus: Failed to grab maple DMA IRQ\n");
+               goto cleanup_dma;
+       }
+
+       /* set up VBLANK interrupt handler */
+       retval = maple_set_vblank_interrupt_handler();
+       if (retval) {
+               printk(KERN_INFO "Maple bus: Failed to grab VBLANK IRQ\n");
+               goto cleanup_irq;
+       }
+
+       maple_queue_cache =
+           kmem_cache_create("maple_queue_cache", 0x400, 0,
+                             SLAB_HWCACHE_ALIGN, NULL);
+
+       if (!maple_queue_cache)
+               goto cleanup_bothirqs;
+
+       /* setup maple ports */
+       for (i = 0; i < MAPLE_PORTS; i++) {
+               mdev[i] = maple_alloc_dev(i, 0);
+               if (!mdev[i]) {
+                       while (i-- > 0)
+                               maple_free_dev(mdev[i]);
+                       goto cleanup_cache;
+               }
+               mdev[i]->registered = 0;
+               mdev[i]->mq->command = MAPLE_COMMAND_DEVINFO;
+               mdev[i]->mq->length = 0;
+               maple_attach_driver(mdev[i]);
+               maple_add_packet(mdev[i]->mq);
+               subdevice_map[i] = 0;
+       }
+
+       /* setup maplebus hardware */
+       maplebus_dma_reset();
+
+       /* initial detection */
+       maple_send();
+
+       maple_pnp_time = jiffies;
+
+       printk(KERN_INFO "Maple bus core now registered.\n");
+
+       return 0;
+
+cleanup_cache:
+       kmem_cache_destroy(maple_queue_cache);
+
+cleanup_bothirqs:
+       free_irq(HW_EVENT_VSYNC, 0);
+
+cleanup_irq:
+       free_irq(HW_EVENT_MAPLE_DMA, 0);
+
+cleanup_dma:
+       free_pages((unsigned long) maple_sendbuf, MAPLE_DMA_PAGES);
+
+cleanup_basic:
+       driver_unregister(&maple_dummy_driver.drv);
+
+cleanup_bus:
+       bus_unregister(&maple_bus_type);
+
+cleanup_device:
+       device_unregister(&maple_bus);
+
+cleanup:
+       printk(KERN_INFO "Maple bus registration failed\n");
+       return retval;
+}
+subsys_initcall(maple_bus_init);