[PATCH] Driver core: allow struct device to have a dev_t

This is the first step in moving class_device to being replaced by
struct device.  It allows struct device to export a dev_t and makes it
easy to dynamically create and destroy struct device as long as they are
associated with a specific class.

Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 176 insertions, 1 deletions

diff --git a/drivers/base/class.c b/drivers/base/class.c
index 41a8e0934e3a..50e841a33af0 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -142,6 +142,7 @@ int class_register(struct class * cls)
         pr_debug("device class '%s': registering\n", cls->name);
 
         INIT_LIST_HEAD(&cls->children);
+        INIT_LIST_HEAD(&cls->devices);
         INIT_LIST_HEAD(&cls->interfaces);
         init_MUTEX(&cls->sem);
         error = kobject_set_name(&cls->subsys.kset.kobj, "%s", cls->name);
diff --git a/drivers/base/core.c b/drivers/base/core.c
index d5e15a03584e..252cf403f891 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/kdev_t.h>
 
 #include <asm/semaphore.h>
 
@@ -98,6 +99,8 @@ static int dev_uevent_filter(struct kset *kset, struct kobject *kobj)
                 struct device *dev = to_dev(kobj);
                 if (dev->bus)
                         return 1;
+                if (dev->class)
+                        return 1;
         }
         return 0;
 }
@@ -106,7 +109,11 @@ static const char *dev_uevent_name(struct kset *kset, struct kobject *kobj)
 {
         struct device *dev = to_dev(kobj);
 
-        return dev->bus->name;
+        if (dev->bus)
+                return dev->bus->name;
+        if (dev->class)
+                return dev->class->name;
+        return NULL;
 }
 
 static int dev_uevent(struct kset *kset, struct kobject *kobj, char **envp,
@@ -117,6 +124,16 @@ static int dev_uevent(struct kset *kset, struct kobject *kobj, char **envp,
         int length = 0;
         int retval = 0;
 
+        /* add the major/minor if present */
+        if (MAJOR(dev->devt)) {
+                add_uevent_var(envp, num_envp, &i,
+                               buffer, buffer_size, &length,
+                               "MAJOR=%u", MAJOR(dev->devt));
+                add_uevent_var(envp, num_envp, &i,
+                               buffer, buffer_size, &length,
+                               "MINOR=%u", MINOR(dev->devt));
+        }
+
         /* add bus name of physical device */
         if (dev->bus)
                 add_uevent_var(envp, num_envp, &i,
@@ -161,6 +178,12 @@ static ssize_t store_uevent(struct device *dev, struct device_attribute *attr,
         return count;
 }
 
+static ssize_t show_dev(struct device *dev, struct device_attribute *attr,
+                        char *buf)
+{
+        return print_dev_t(buf, dev->devt);
+}
+
 /*
  *      devices_subsys - structure to be registered with kobject core.
  */
@@ -231,6 +254,7 @@ void device_initialize(struct device *dev)
         klist_init(&dev->klist_children, klist_children_get,
                    klist_children_put);
         INIT_LIST_HEAD(&dev->dma_pools);
+        INIT_LIST_HEAD(&dev->node);
         init_MUTEX(&dev->sem);
         device_init_wakeup(dev, 0);
 }
@@ -274,6 +298,31 @@ int device_add(struct device *dev)
         dev->uevent_attr.store = store_uevent;
         device_create_file(dev, &dev->uevent_attr);
 
+        if (MAJOR(dev->devt)) {
+                struct device_attribute *attr;
+                attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+                if (!attr) {
+                        error = -ENOMEM;
+                        goto PMError;
+                }
+                attr->attr.name = "dev";
+                attr->attr.mode = S_IRUGO;
+                if (dev->driver)
+                        attr->attr.owner = dev->driver->owner;
+                attr->show = show_dev;
+                error = device_create_file(dev, attr);
+                if (error) {
+                        kfree(attr);
+                        goto attrError;
+                }
+
+                dev->devt_attr = attr;
+        }
+
+        if (dev->class)
+                sysfs_create_link(&dev->class->subsys.kset.kobj, &dev->kobj,
+                                  dev->bus_id);
+
         if ((error = device_pm_add(dev)))
                 goto PMError;
         if ((error = bus_add_device(dev)))
@@ -292,6 +341,11 @@ int device_add(struct device *dev)
  BusError:
         device_pm_remove(dev);
  PMError:
+        if (dev->devt_attr) {
+                device_remove_file(dev, dev->devt_attr);
+                kfree(dev->devt_attr);
+        }
+ attrError:
         kobject_uevent(&dev->kobj, KOBJ_REMOVE);
         kobject_del(&dev->kobj);
  Error:
@@ -366,6 +420,10 @@ void device_del(struct device * dev)
 
         if (parent)
                 klist_del(&dev->knode_parent);
+        if (dev->devt_attr)
+                device_remove_file(dev, dev->devt_attr);
+        if (dev->class)
+                sysfs_remove_link(&dev->class->subsys.kset.kobj, dev->bus_id);
         device_remove_file(dev, &dev->uevent_attr);
 
         /* Notify the platform of the removal, in case they
@@ -450,3 +508,105 @@ EXPORT_SYMBOL_GPL(put_device);
 
 EXPORT_SYMBOL_GPL(device_create_file);
 EXPORT_SYMBOL_GPL(device_remove_file);
+
+
+static void device_create_release(struct device *dev)
+{
+        pr_debug("%s called for %s\n", __FUNCTION__, dev->bus_id);
+        kfree(dev);
+}
+
+/**
+ * device_create - creates a device and registers it with sysfs
+ * @cs: pointer to the struct class that this device should be registered to.
+ * @parent: pointer to the parent struct device of this new device, if any.
+ * @dev: the dev_t for the char device to be added.
+ * @fmt: string for the class device's name
+ *
+ * This function can be used by char device classes.  A struct
+ * device will be created in sysfs, registered to the specified
+ * class.
+ * A "dev" file will be created, showing the dev_t for the device, if
+ * the dev_t is not 0,0.
+ * If a pointer to a parent struct device is passed in, the newly
+ * created struct device will be a child of that device in sysfs.  The
+ * pointer to the struct device will be returned from the call.  Any
+ * further sysfs files that might be required can be created using this
+ * pointer.
+ *
+ * Note: the struct class passed to this function must have previously
+ * been created with a call to class_create().
+ */
+struct device *device_create(struct class *class, struct device *parent,
+                             dev_t devt, char *fmt, ...)
+{
+        va_list args;
+        struct device *dev = NULL;
+        int retval = -ENODEV;
+
+        if (class == NULL || IS_ERR(class))
+                goto error;
+        if (parent == NULL) {
+                printk(KERN_WARNING "%s does not work yet for NULL parents\n", __FUNCTION__);
+                goto error;
+        }
+
+        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+        if (!dev) {
+                retval = -ENOMEM;
+                goto error;
+        }
+
+        dev->devt = devt;
+        dev->class = class;
+        dev->parent = parent;
+        dev->release = device_create_release;
+
+        va_start(args, fmt);
+        vsnprintf(dev->bus_id, BUS_ID_SIZE, fmt, args);
+        va_end(args);
+        retval = device_register(dev);
+        if (retval)
+                goto error;
+
+        /* tie the class to the device */
+        down(&class->sem);
+        list_add_tail(&dev->node, &class->devices);
+        up(&class->sem);
+
+        return dev;
+
+error:
+        kfree(dev);
+        return ERR_PTR(retval);
+}
+EXPORT_SYMBOL_GPL(device_create);
+
+/**
+ * device_destroy - removes a device that was created with device_create()
+ * @class: the pointer to the struct class that this device was registered * with.
+ * @dev: the dev_t of the device that was previously registered.
+ *
+ * This call unregisters and cleans up a class device that was created with a
+ * call to class_device_create()
+ */
+void device_destroy(struct class *class, dev_t devt)
+{
+        struct device *dev = NULL;
+        struct device *dev_tmp;
+
+        down(&class->sem);
+        list_for_each_entry(dev_tmp, &class->devices, node) {
+                if (dev_tmp->devt == devt) {
+                        dev = dev_tmp;
+                        break;
+                }
+        }
+        up(&class->sem);
+
+        if (dev) {
+                list_del_init(&dev->node);
+                device_unregister(dev);
+        }
+}
+EXPORT_SYMBOL_GPL(device_destroy);
diff --git a/include/linux/device.h b/include/linux/device.h
index ade10dd6b779..b473f4278910 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -142,6 +142,7 @@ struct class {
 
         struct subsystem        subsys;
         struct list_head        children;
+        struct list_head        devices;
         struct list_head        interfaces;
         struct semaphore        sem;    /* locks both the children and interfaces lists */
 
@@ -305,6 +306,7 @@ struct device {
         struct kobject kobj;
         char    bus_id[BUS_ID_SIZE];    /* position on parent bus */
         struct device_attribute uevent_attr;
+        struct device_attribute *devt_attr;
 
         struct semaphore        sem;    /* semaphore to synchronize calls to
                                          * its driver.
@@ -332,6 +334,11 @@ struct device {
         struct dma_coherent_mem *dma_mem; /* internal for coherent mem
                                              override */
 
+        /* class_device migration path */
+        struct list_head        node;
+        struct class            *class;         /* optional*/
+        dev_t                   devt;           /* dev_t, creates the sysfs "dev" */
+
         void    (*release)(struct device * dev);
 };
 
@@ -373,6 +380,13 @@ extern int  device_attach(struct device * dev);
 extern void driver_attach(struct device_driver * drv);
 extern void device_reprobe(struct device *dev);
 
+/*
+ * Easy functions for dynamically creating devices on the fly
+ */
+extern struct device *device_create(struct class *cls, struct device *parent,
+                                    dev_t devt, char *fmt, ...)
+                                    __attribute__((format(printf,4,5)));
+extern void device_destroy(struct class *cls, dev_t devt);
 
 /*
  * Platform "fixup" functions - allow the platform to have their say