1/*
2 *    HMC Drive CD/DVD Device
3 *
4 *    Copyright IBM Corp. 2013
5 *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
6 *
7 *    This file provides a Linux "misc" character device for access to an
8 *    assigned HMC drive CD/DVD-ROM. It works as follows: First create the
9 *    device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,
10 *    SEEK_END) indicates that a new FTP command follows (not needed on the
11 *    first command after open). Then write() the FTP command ASCII string
12 *    to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the
13 *    end read() the response.
14 */
15
16#define KMSG_COMPONENT "hmcdrv"
17#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
18
19#include <linux/kernel.h>
20#include <linux/module.h>
21#include <linux/slab.h>
22#include <linux/fs.h>
23#include <linux/cdev.h>
24#include <linux/miscdevice.h>
25#include <linux/device.h>
26#include <linux/capability.h>
27#include <linux/delay.h>
28#include <linux/uaccess.h>
29
30#include "hmcdrv_dev.h"
31#include "hmcdrv_ftp.h"
32
33/* If the following macro is defined, then the HMC device creates it's own
34 * separated device class (and dynamically assigns a major number). If not
35 * defined then the HMC device is assigned to the "misc" class devices.
36 *
37#define HMCDRV_DEV_CLASS "hmcftp"
38 */
39
40#define HMCDRV_DEV_NAME  "hmcdrv"
41#define HMCDRV_DEV_BUSY_DELAY	 500 /* delay between -EBUSY trials in ms */
42#define HMCDRV_DEV_BUSY_RETRIES  3   /* number of retries on -EBUSY */
43
44struct hmcdrv_dev_node {
45
46#ifdef HMCDRV_DEV_CLASS
47	struct cdev dev; /* character device structure */
48	umode_t mode;	 /* mode of device node (unused, zero) */
49#else
50	struct miscdevice dev; /* "misc" device structure */
51#endif
52
53};
54
55static int hmcdrv_dev_open(struct inode *inode, struct file *fp);
56static int hmcdrv_dev_release(struct inode *inode, struct file *fp);
57static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence);
58static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
59			       size_t len, loff_t *pos);
60static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
61				size_t len, loff_t *pos);
62static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
63				   char __user *buf, size_t len);
64
65/*
66 * device operations
67 */
68static const struct file_operations hmcdrv_dev_fops = {
69	.open = hmcdrv_dev_open,
70	.llseek = hmcdrv_dev_seek,
71	.release = hmcdrv_dev_release,
72	.read = hmcdrv_dev_read,
73	.write = hmcdrv_dev_write,
74};
75
76static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */
77
78#ifdef HMCDRV_DEV_CLASS
79
80static struct class *hmcdrv_dev_class; /* device class pointer */
81static dev_t hmcdrv_dev_no; /* device number (major/minor) */
82
83/**
84 * hmcdrv_dev_name() - provides a naming hint for a device node in /dev
85 * @dev: device for which the naming/mode hint is
86 * @mode: file mode for device node created in /dev
87 *
88 * See: devtmpfs.c, function devtmpfs_create_node()
89 *
90 * Return: recommended device file name in /dev
91 */
92static char *hmcdrv_dev_name(struct device *dev, umode_t *mode)
93{
94	char *nodename = NULL;
95	const char *devname = dev_name(dev); /* kernel device name */
96
97	if (devname)
98		nodename = kasprintf(GFP_KERNEL, "%s", devname);
99
100	/* on device destroy (rmmod) the mode pointer may be NULL
101	 */
102	if (mode)
103		*mode = hmcdrv_dev.mode;
104
105	return nodename;
106}
107
108#endif	/* HMCDRV_DEV_CLASS */
109
110/*
111 * open()
112 */
113static int hmcdrv_dev_open(struct inode *inode, struct file *fp)
114{
115	int rc;
116
117	/* check for non-blocking access, which is really unsupported
118	 */
119	if (fp->f_flags & O_NONBLOCK)
120		return -EINVAL;
121
122	/* Because it makes no sense to open this device read-only (then a
123	 * FTP command cannot be emitted), we respond with an error.
124	 */
125	if ((fp->f_flags & O_ACCMODE) == O_RDONLY)
126		return -EINVAL;
127
128	/* prevent unloading this module as long as anyone holds the
129	 * device file open - so increment the reference count here
130	 */
131	if (!try_module_get(THIS_MODULE))
132		return -ENODEV;
133
134	fp->private_data = NULL; /* no command yet */
135	rc = hmcdrv_ftp_startup();
136	if (rc)
137		module_put(THIS_MODULE);
138
139	pr_debug("open file '/dev/%pD' with return code %d\n", fp, rc);
140	return rc;
141}
142
143/*
144 * release()
145 */
146static int hmcdrv_dev_release(struct inode *inode, struct file *fp)
147{
148	pr_debug("closing file '/dev/%pD'\n", fp);
149	kfree(fp->private_data);
150	fp->private_data = NULL;
151	hmcdrv_ftp_shutdown();
152	module_put(THIS_MODULE);
153	return 0;
154}
155
156/*
157 * lseek()
158 */
159static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence)
160{
161	switch (whence) {
162	case SEEK_CUR: /* relative to current file position */
163		pos += fp->f_pos; /* new position stored in 'pos' */
164		break;
165
166	case SEEK_SET: /* absolute (relative to beginning of file) */
167		break; /* SEEK_SET */
168
169		/* We use SEEK_END as a special indicator for a SEEK_SET
170		 * (set absolute position), combined with a FTP command
171		 * clear.
172		 */
173	case SEEK_END:
174		if (fp->private_data) {
175			kfree(fp->private_data);
176			fp->private_data = NULL;
177		}
178
179		break; /* SEEK_END */
180
181	default: /* SEEK_DATA, SEEK_HOLE: unsupported */
182		return -EINVAL;
183	}
184
185	if (pos < 0)
186		return -EINVAL;
187
188	if (fp->f_pos != pos)
189		++fp->f_version;
190
191	fp->f_pos = pos;
192	return pos;
193}
194
195/*
196 * transfer (helper function)
197 */
198static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
199				   char __user *buf, size_t len)
200{
201	ssize_t retlen;
202	unsigned trials = HMCDRV_DEV_BUSY_RETRIES;
203
204	do {
205		retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);
206
207		if (retlen != -EBUSY)
208			break;
209
210		msleep(HMCDRV_DEV_BUSY_DELAY);
211
212	} while (--trials > 0);
213
214	return retlen;
215}
216
217/*
218 * read()
219 */
220static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
221			       size_t len, loff_t *pos)
222{
223	ssize_t retlen;
224
225	if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
226	    (fp->private_data == NULL)) { /* no FTP cmd defined ? */
227		return -EBADF;
228	}
229
230	retlen = hmcdrv_dev_transfer((char *) fp->private_data,
231				     *pos, ubuf, len);
232
233	pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",
234		 fp, (long long) *pos, retlen, len);
235
236	if (retlen > 0)
237		*pos += retlen;
238
239	return retlen;
240}
241
242/*
243 * write()
244 */
245static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
246				size_t len, loff_t *pos)
247{
248	ssize_t retlen;
249
250	pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",
251		 fp, (long long) *pos, len);
252
253	if (!fp->private_data) { /* first expect a cmd write */
254		fp->private_data = kmalloc(len + 1, GFP_KERNEL);
255
256		if (!fp->private_data)
257			return -ENOMEM;
258
259		if (!copy_from_user(fp->private_data, ubuf, len)) {
260			((char *)fp->private_data)[len] = '\0';
261			return len;
262		}
263
264		kfree(fp->private_data);
265		fp->private_data = NULL;
266		return -EFAULT;
267	}
268
269	retlen = hmcdrv_dev_transfer((char *) fp->private_data,
270				     *pos, (char __user *) ubuf, len);
271	if (retlen > 0)
272		*pos += retlen;
273
274	pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);
275
276	return retlen;
277}
278
279/**
280 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device
281 *
282 * This function creates a HMC drive CD/DVD kernel device and an associated
283 * device under /dev, using a dynamically allocated major number.
284 *
285 * Return: 0 on success, else an error code.
286 */
287int hmcdrv_dev_init(void)
288{
289	int rc;
290
291#ifdef HMCDRV_DEV_CLASS
292	struct device *dev;
293
294	rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);
295
296	if (rc)
297		goto out_err;
298
299	cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
300	hmcdrv_dev.dev.owner = THIS_MODULE;
301	rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);
302
303	if (rc)
304		goto out_unreg;
305
306	/* At this point the character device exists in the kernel (see
307	 * /proc/devices), but not under /dev nor /sys/devices/virtual. So
308	 * we have to create an associated class (see /sys/class).
309	 */
310	hmcdrv_dev_class = class_create(THIS_MODULE, HMCDRV_DEV_CLASS);
311
312	if (IS_ERR(hmcdrv_dev_class)) {
313		rc = PTR_ERR(hmcdrv_dev_class);
314		goto out_devdel;
315	}
316
317	/* Finally a device node in /dev has to be established (as 'mkdev'
318	 * does from the command line). Notice that assignment of a device
319	 * node name/mode function is optional (only for mode != 0600).
320	 */
321	hmcdrv_dev.mode = 0; /* "unset" */
322	hmcdrv_dev_class->devnode = hmcdrv_dev_name;
323
324	dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
325			    "%s", HMCDRV_DEV_NAME);
326	if (!IS_ERR(dev))
327		return 0;
328
329	rc = PTR_ERR(dev);
330	class_destroy(hmcdrv_dev_class);
331	hmcdrv_dev_class = NULL;
332
333out_devdel:
334	cdev_del(&hmcdrv_dev.dev);
335
336out_unreg:
337	unregister_chrdev_region(hmcdrv_dev_no, 1);
338
339out_err:
340
341#else  /* !HMCDRV_DEV_CLASS */
342	hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
343	hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
344	hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
345	hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
346	rc = misc_register(&hmcdrv_dev.dev);
347#endif	/* HMCDRV_DEV_CLASS */
348
349	return rc;
350}
351
352/**
353 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
354 */
355void hmcdrv_dev_exit(void)
356{
357#ifdef HMCDRV_DEV_CLASS
358	if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
359		device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
360		class_destroy(hmcdrv_dev_class);
361	}
362
363	cdev_del(&hmcdrv_dev.dev);
364	unregister_chrdev_region(hmcdrv_dev_no, 1);
365#else  /* !HMCDRV_DEV_CLASS */
366	misc_deregister(&hmcdrv_dev.dev);
367#endif	/* HMCDRV_DEV_CLASS */
368}
369