Linux Device Drivers 3 examples

1 files changed, 177 insertions, 0 deletions

diff --git a/lddbus/lddbus.c b/lddbus/lddbus.c
new file mode 100644
index 0000000..be37c6c
--- /dev/null
+++ b/lddbus/lddbus.c
@@ -0,0 +1,177 @@
+/*
+ * A virtual bus for LDD sample code devices to plug into.  This
+ * code is heavily borrowed from drivers/base/sys.c
+ *
+ * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
+ * Copyright (C) 2001 O'Reilly & Associates
+ *
+ * The source code in this file can be freely used, adapted,
+ * and redistributed in source or binary form, so long as an
+ * acknowledgment appears in derived source files.  The citation
+ * should list that the code comes from the book "Linux Device
+ * Drivers" by Alessandro Rubini and Jonathan Corbet, published
+ * by O'Reilly & Associates.   No warranty is attached;
+ * we cannot take responsibility for errors or fitness for use.
+ *
+ */
+/* $Id: lddbus.c,v 1.9 2004/09/26 08:12:27 gregkh Exp $ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include "lddbus.h"
+
+MODULE_AUTHOR("Jonathan Corbet");
+MODULE_LICENSE("Dual BSD/GPL");
+static char *Version = "$Revision: 1.9 $";
+
+/*
+ * Respond to hotplug events.
+ */
+static int ldd_hotplug(struct device *dev, char **envp, int num_envp,
+		char *buffer, int buffer_size)
+{
+	envp[0] = buffer;
+	if (snprintf(buffer, buffer_size, "LDDBUS_VERSION=%s",
+			    Version) >= buffer_size)
+		return -ENOMEM;
+	envp[1] = NULL;
+	return 0;
+}
+
+/*
+ * Match LDD devices to drivers.  Just do a simple name test.
+ */
+static int ldd_match(struct device *dev, struct device_driver *driver)
+{
+	return !strncmp(dev->bus_id, driver->name, strlen(driver->name));
+}
+
+
+/*
+ * The LDD bus device.
+ */
+static void ldd_bus_release(struct device *dev)
+{
+	printk(KERN_DEBUG "lddbus release\n");
+}
+	
+struct device ldd_bus = {
+	.bus_id   = "ldd0",
+	.release  = ldd_bus_release
+};
+
+
+/*
+ * And the bus type.
+ */
+struct bus_type ldd_bus_type = {
+	.name = "ldd",
+	.match = ldd_match,
+	.hotplug  = ldd_hotplug,
+};
+
+/*
+ * Export a simple attribute.
+ */
+static ssize_t show_bus_version(struct bus_type *bus, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%s\n", Version);
+}
+
+static BUS_ATTR(version, S_IRUGO, show_bus_version, NULL);
+
+
+
+/*
+ * LDD devices.
+ */
+
+/*
+ * For now, no references to LDDbus devices go out which are not
+ * tracked via the module reference count, so we use a no-op
+ * release function.
+ */
+static void ldd_dev_release(struct device *dev)
+{ }
+
+int register_ldd_device(struct ldd_device *ldddev)
+{
+	ldddev->dev.bus = &ldd_bus_type;
+	ldddev->dev.parent = &ldd_bus;
+	ldddev->dev.release = ldd_dev_release;
+	strncpy(ldddev->dev.bus_id, ldddev->name, BUS_ID_SIZE);
+	return device_register(&ldddev->dev);
+}
+EXPORT_SYMBOL(register_ldd_device);
+
+void unregister_ldd_device(struct ldd_device *ldddev)
+{
+	device_unregister(&ldddev->dev);
+}
+EXPORT_SYMBOL(unregister_ldd_device);
+
+/*
+ * Crude driver interface.
+ */
+
+
+static ssize_t show_version(struct device_driver *driver, char *buf)
+{
+	struct ldd_driver *ldriver = to_ldd_driver(driver);
+
+	sprintf(buf, "%s\n", ldriver->version);
+	return strlen(buf);
+}
+		
+
+int register_ldd_driver(struct ldd_driver *driver)
+{
+	int ret;
+	
+	driver->driver.bus = &ldd_bus_type;
+	ret = driver_register(&driver->driver);
+	if (ret)
+		return ret;
+	driver->version_attr.attr.name = "version";
+	driver->version_attr.attr.owner = driver->module;
+	driver->version_attr.attr.mode = S_IRUGO;
+	driver->version_attr.show = show_version;
+	driver->version_attr.store = NULL;
+	return driver_create_file(&driver->driver, &driver->version_attr);
+}
+
+void unregister_ldd_driver(struct ldd_driver *driver)
+{
+	driver_unregister(&driver->driver);
+}
+EXPORT_SYMBOL(register_ldd_driver);
+EXPORT_SYMBOL(unregister_ldd_driver);
+
+
+
+static int __init ldd_bus_init(void)
+{
+	int ret;
+
+	ret = bus_register(&ldd_bus_type);
+	if (ret)
+		return ret;
+	if (bus_create_file(&ldd_bus_type, &bus_attr_version))
+		printk(KERN_NOTICE "Unable to create version attribute\n");
+	ret = device_register(&ldd_bus);
+	if (ret)
+		printk(KERN_NOTICE "Unable to register ldd0\n");
+	return ret;
+}
+
+static void ldd_bus_exit(void)
+{
+	device_unregister(&ldd_bus);
+	bus_unregister(&ldd_bus_type);
+}
+
+module_init(ldd_bus_init);
+module_exit(ldd_bus_exit);