Linux Device Drivers 3 examples

Author: martinezjavier

LICENSE

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+
+
+Unless  otherwise stated, the  source code distributed  with this book
+can   be  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 BOOK  by AUTHOR, published by O'Reilly &
+Associates.  This  code is under copyright and  cannot be  included in
+any other book, publication, or educational product without permission
+from O'Reilly &  Associates. No warranty  is attached; we  cannot take
+responsibility for errors or fitness for use.
+
+
+There are a few exception to this licence, however: a few sources
+herein are distributed according to the GNU General Public License,
+version 2. You'll find a copy of the license in
+/usr/src/linux/COPYING, and in other places in your filesystem. The
+affected source files are:
+
+	pci/pci_skel.c
+	tty/tiny_serial.c
+	tty/tiny_tty.c
+	usb/usb-skeleton.c
+
+The files in ./pci ./tty and ./usb inherit the GPL from the kernel
+sources, as most of their code comes straight from the kernel
+(usb-skeleton.c being part of the kernel source tree directly.)
+

Makefile

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+
+SUBDIRS =  misc-progs misc-modules \
+           skull scull scullc sculld scullp scullv sbull snull\
+	   short shortprint pci simple usb tty lddbus
+
+all: subdirs
+
+subdirs:
+	for n in $(SUBDIRS); do $(MAKE) -C $$n || exit 1; done
+
+clean:
+	for n in $(SUBDIRS); do $(MAKE) -C $$n clean; done

include/lddbus.h

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+/*
+ * Definitions for the virtual LDD bus.
+ *
+ * $Id: lddbus.h,v 1.4 2004/08/20 18:49:44 corbet Exp $
+ */
+
+//extern struct device ldd_bus;
+extern struct bus_type ldd_bus_type;
+
+
+/*
+ * The LDD driver type.
+ */
+
+struct ldd_driver {
+	char *version;
+	struct module *module;
+	struct device_driver driver;
+	struct driver_attribute version_attr;
+};
+
+#define to_ldd_driver(drv) container_of(drv, struct ldd_driver, driver);
+
+/*
+ * A device type for things "plugged" into the LDD bus.
+ */
+
+struct ldd_device {
+	char *name;
+	struct ldd_driver *driver;
+	struct device dev;
+};
+
+#define to_ldd_device(dev) container_of(dev, struct ldd_device, dev);
+
+extern int register_ldd_device(struct ldd_device *);
+extern void unregister_ldd_device(struct ldd_device *);
+extern int register_ldd_driver(struct ldd_driver *);
+extern void unregister_ldd_driver(struct ldd_driver *);

lddbus/Makefile

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+# Comment/uncomment the following line to disable/enable debugging
+#DEBUG = y
+
+# Add your debugging flag (or not) to CFLAGS
+ifeq ($(DEBUG),y)
+  DEBFLAGS = -O -g # "-O" is needed to expand inlines
+else
+  DEBFLAGS = -O2
+endif
+CFLAGS  += $(DEBFLAGS) -I$(LDDINCDIR)
+
+
+ifneq ($(KERNELRELEASE),)
+# call from kernel build system
+
+obj-m	:= lddbus.o
+
+else
+
+KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+PWD       := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KERNELDIR) SUBDIRS=$(PWD) LDDINCDIR=$(PWD)/../include modules
+
+endif
+
+
+
+clean:
+	rm -rf *.o *.ko *~ core .depend *.mod.c .*.cmd .tmp_versions .*.o.d
+
+depend .depend dep:
+	$(CC) $(CFLAGS) -M *.c > .depend
+
+
+ifeq (.depend,$(wildcard .depend))
+include .depend
+endif

lddbus/lddbus.c

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+/*
+ * 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);

misc-modules/Makefile

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+
+# To build modules outside of the kernel tree, we run "make"
+# in the kernel source tree; the Makefile these then includes this
+# Makefile once again.
+# This conditional selects whether we are being included from the
+# kernel Makefile or not.
+ifeq ($(KERNELRELEASE),)
+
+    # Assume the source tree is where the running kernel was built
+    # You should set KERNELDIR in the environment if it's elsewhere
+    KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+    # The current directory is passed to sub-makes as argument
+    PWD := $(shell pwd)
+
+modules:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+
+modules_install:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install
+
+clean:
+	rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
+
+.PHONY: modules modules_install clean
+
+else
+    # called from kernel build system: just declare what our modules are
+    obj-m := hello.o hellop.o seq.o jit.o jiq.o sleepy.o complete.o \
+             silly.o faulty.o kdatasize.o kdataalign.o
+endif
+
+