GSoC Warm Up Kernel Task

drivers/char/Kconfig

@@ -535,6 +535,12 @@ config ADI
 	  and SSM (Silicon Secured Memory).  Intended consumers of this
 	  driver include crash and makedumpfile.
 
+config GSOC_DUMMY_CHAR_DEVICE
+	tristate "GSoC Warmup Driver"
+	help
+	This builds the GSoC Dummy Char Driver, which is required for the warmup task.
+	Say Y to build it into the kernel, M to build it as a module and N to not build it.
+
 endmenu
 
 config RANDOM_TRUST_CPU
@@ -559,4 +565,5 @@ config RANDOM_TRUST_BOOTLOADER
 	device randomness. Say Y here to assume the entropy provided by the
 	booloader is trustworthy so it will be added to the kernel's entropy
 	pool. Otherwise, say N here so it will be regarded as device input that
-	only mixes the entropy pool.
+	only mixes the entropy pool.
+

drivers/char/Makefile

@@ -52,3 +52,5 @@ js-rtc-y = rtc.o
 obj-$(CONFIG_XILLYBUS)		+= xillybus/
 obj-$(CONFIG_POWERNV_OP_PANEL)	+= powernv-op-panel.o
 obj-$(CONFIG_ADI)		+= adi.o
+
+obj-$(CONFIG_GSOC_DUMMY_CHAR_DEVICE)    += gsoc-dummy-char-dev.o

drivers/char/gsoc-dummy-char-dev.c

@@ -0,0 +1,140 @@
+/*
+ * GSoC Dummy Driver for warm up exercise
+ *
+ * Author:	Niklas Wantrupp <[email protected]>
+ *        	based on
+ * 				Dummy character driver by
+ *				John Madieu <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/version.h>
+#include <linux/device.h>
+#include <linux/cdev.h>
+#include <linux/uaccess.h>
+
+static int gsoc_char_dev_open(struct inode * inode, struct file * file);
+static int gsoc_char_dev_close(struct inode * inode, struct file * file);
+static ssize_t gsoc_char_dev_read(struct file *file, char __user * buf, size_t count,
+                                loff_t * offset);
+static ssize_t gsoc_char_dev_write(struct file * file, const char __user * buf, size_t count,
+                                loff_t * offset);
+static int gsoc_char_dev_uevent(struct device *dev, struct kobj_uevent_env *env);
+
+static unsigned int major;
+static struct class *gsoc_dummy_class;
+static struct cdev gsoc_dummy_device;
+
+static const struct file_operations gsoc_dummy_dev_file_ops = {
+    .open = gsoc_char_dev_open,
+    .release = gsoc_char_dev_close,
+    .read = gsoc_char_dev_read,
+    .write = gsoc_char_dev_write,
+};
+
+static int __init gsoc_dummy_char_dev_init_module(void)
+{
+    struct device *dummy_device;
+    int err;
+    dev_t gsoc_dev;
+
+    // register a range of char dev numbers 0 to 1 in this case
+    err = alloc_chrdev_region(&gsoc_dev, 0, 1, "gsoc_dummy_char_dev");
+    if (err < 0) {
+        pr_err("Can't get major number\n");
+        return err;
+    }
+    major = MAJOR(gsoc_dev);
+    pr_info("gsoc_dummy_char_dev major number = %d\n",major);
+
+    // Create sysfs class
+    gsoc_dummy_class = class_create(THIS_MODULE, "gsoc_dummy_char_dev_class");
+
+    if (IS_ERR(gsoc_dummy_class)) {
+        pr_err("GSoC char device class could not be created.\n");
+        unregister_chrdev_region(MKDEV(major, 0), 1);
+        return PTR_ERR(gsoc_dummy_class);
+    }
+
+    gsoc_dummy_class->dev_uevent = gsoc_char_dev_uevent;
+
+    // Create device and bind file ops
+    cdev_init(&gsoc_dummy_device, &gsoc_dummy_dev_file_ops);
+    gsoc_dummy_device.owner = THIS_MODULE;
+
+    // add device to system
+    cdev_add(&gsoc_dummy_device, gsoc_dev, 1);
+
+    // create device node
+    dummy_device = device_create(gsoc_dummy_class, NULL, gsoc_dev, NULL, "gsoc_dummy_char_dev"); 
+
+    if (IS_ERR(dummy_device)) {
+        pr_err("GSoC char device could not be created.\n");
+        class_destroy(gsoc_dummy_class);
+        unregister_chrdev_region(gsoc_dev, 1);
+        return -1;
+    }
+
+    pr_info("loaded GSoC dummy driver\n");
+    return 0;
+}
+
+static void __exit gsoc_dummy_char_dev_exit_module(void)
+{
+    unregister_chrdev_region(MKDEV(major, 0), 1);
+    device_destroy(gsoc_dummy_class, MKDEV(major, 0));
+    cdev_del(&gsoc_dummy_device);
+    class_destroy(gsoc_dummy_class);
+
+    pr_info("unloaded GSoC dummy driver\n");
+}
+
+static int gsoc_char_dev_open(struct inode * inode, struct file * file)
+{
+    pr_info("Open function of GSoC dummy driver called.\n");
+    return 0;
+}
+
+static int gsoc_char_dev_close(struct inode * inode, struct file * file)
+{
+    pr_info("Close function of GSoC dummy driver called.\n");
+    return 0;
+}
+
+static ssize_t gsoc_char_dev_read(struct file *file, char __user * buf, size_t count,
+                                loff_t * offset)
+{
+    pr_info("Read function of GSoC dummy driver called.\n");
+    return 0;
+}
+
+static ssize_t gsoc_char_dev_write(struct file * file, const char __user * buf, size_t count,
+                                loff_t * offset)
+{
+    pr_info("Write function of GSoC dummy driver called.\n");
+    return count;
+}
+
+static int gsoc_char_dev_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+    add_uevent_var(env, "DEVMODE=%#o", 0666);
+    return 0;
+}
+
+module_init(gsoc_dummy_char_dev_init_module);
+module_exit(gsoc_dummy_char_dev_exit_module);
+
+MODULE_AUTHOR("Niklas Wantrupp <[email protected]>");
+MODULE_DESCRIPTION("GSoC warm up dummy char device driver");
+MODULE_LICENSE("GPL");