增加了LLD3书中的代码...

linux_device_driver_v3/snull/Makefile

@@ -0,0 +1,41 @@
+# 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 -DSBULL_DEBUG # "-O" is needed to expand inlines
+else
+  DEBFLAGS = -O2
+endif
+
+CFLAGS += $(DEBFLAGS)
+CFLAGS += -I..
+
+ifneq ($(KERNELRELEASE),)
+# call from kernel build system
+
+obj-m	:= snull.o
+
+else
+
+KERNELDIR ?= /lib/modules/$(shell uname -r)/build
+PWD       := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+
+endif
+
+
+
+clean:
+	rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
+
+depend .depend dep:
+	$(CC) $(CFLAGS) -M *.c > .depend
+
+
+ifeq (.depend,$(wildcard .depend))
+include .depend
+endif

linux_device_driver_v3/snull/snull.h

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+
+/*
+ * snull.h -- definitions for the network module
+ *
+ * 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.
+ */
+
+/*
+ * Macros to help debugging
+ */
+
+#undef PDEBUG             /* undef it, just in case */
+#ifdef SNULL_DEBUG
+#  ifdef __KERNEL__
+     /* This one if debugging is on, and kernel space */
+#    define PDEBUG(fmt, args...) printk( KERN_DEBUG "snull: " fmt, ## args)
+#  else
+     /* This one for user space */
+#    define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
+#  endif
+#else
+#  define PDEBUG(fmt, args...) /* not debugging: nothing */
+#endif
+
+#undef PDEBUGG
+#define PDEBUGG(fmt, args...) /* nothing: it's a placeholder */
+
+
+/* These are the flags in the statusword */
+#define SNULL_RX_INTR 0x0001
+#define SNULL_TX_INTR 0x0002
+
+/* Default timeout period */
+#define SNULL_TIMEOUT 5   /* In jiffies */
+
+extern struct net_device *snull_devs[];
+
+
+
+

linux_device_driver_v3/snull/snull_load

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+#!/bin/sh
+
+export PATH=/sbin:/bin
+
+# Use a pathname, as new modutils don't look in the current dir by default
+insmod ./snull.ko $*
+ifconfig sn0 local0
+ifconfig sn1 local1

linux_device_driver_v3/snull/snull_unload

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+#!/bin/sh
+
+/sbin/ifconfig sn0 down
+/sbin/ifconfig sn1 down
+/sbin/rmmod snull