summaryrefslogtreecommitdiffstats
path: root/drivers/s390/char/hmcdrv_dev.c
blob: 20e9cd542e0335b07efceb88e67b9426f7ec2b85 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
// SPDX-License-Identifier: GPL-2.0
/*
 *    HMC Drive CD/DVD Device
 *
 *    Copyright IBM Corp. 2013
 *    Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
 *
 *    This file provides a Linux "misc" character device for access to an
 *    assigned HMC drive CD/DVD-ROM. It works as follows: First create the
 *    device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,
 *    SEEK_END) indicates that a new FTP command follows (not needed on the
 *    first command after open). Then write() the FTP command ASCII string
 *    to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the
 *    end read() the response.
 */

#define KMSG_COMPONENT "hmcdrv"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/miscdevice.h>
#include <linux/device.h>
#include <linux/capability.h>
#include <linux/delay.h>
#include <linux/uaccess.h>

#include "hmcdrv_dev.h"
#include "hmcdrv_ftp.h"

/* If the following macro is defined, then the HMC device creates it's own
 * separated device class (and dynamically assigns a major number). If not
 * defined then the HMC device is assigned to the "misc" class devices.
 *
#define HMCDRV_DEV_CLASS "hmcftp"
 */

#define HMCDRV_DEV_NAME  "hmcdrv"
#define HMCDRV_DEV_BUSY_DELAY	 500 /* delay between -EBUSY trials in ms */
#define HMCDRV_DEV_BUSY_RETRIES  3   /* number of retries on -EBUSY */

struct hmcdrv_dev_node {

#ifdef HMCDRV_DEV_CLASS
	struct cdev dev; /* character device structure */
	umode_t mode;	 /* mode of device node (unused, zero) */
#else
	struct miscdevice dev; /* "misc" device structure */
#endif

};

static int hmcdrv_dev_open(struct inode *inode, struct file *fp);
static int hmcdrv_dev_release(struct inode *inode, struct file *fp);
static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence);
static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
			       size_t len, loff_t *pos);
static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
				size_t len, loff_t *pos);
static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
				   char __user *buf, size_t len);

/*
 * device operations
 */
static const struct file_operations hmcdrv_dev_fops = {
	.open = hmcdrv_dev_open,
	.llseek = hmcdrv_dev_seek,
	.release = hmcdrv_dev_release,
	.read = hmcdrv_dev_read,
	.write = hmcdrv_dev_write,
};

static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */

#ifdef HMCDRV_DEV_CLASS

static struct class *hmcdrv_dev_class; /* device class pointer */
static dev_t hmcdrv_dev_no; /* device number (major/minor) */

/**
 * hmcdrv_dev_name() - provides a naming hint for a device node in /dev
 * @dev: device for which the naming/mode hint is
 * @mode: file mode for device node created in /dev
 *
 * See: devtmpfs.c, function devtmpfs_create_node()
 *
 * Return: recommended device file name in /dev
 */
static char *hmcdrv_dev_name(struct device *dev, umode_t *mode)
{
	char *nodename = NULL;
	const char *devname = dev_name(dev); /* kernel device name */

	if (devname)
		nodename = kasprintf(GFP_KERNEL, "%s", devname);

	/* on device destroy (rmmod) the mode pointer may be NULL
	 */
	if (mode)
		*mode = hmcdrv_dev.mode;

	return nodename;
}

#endif	/* HMCDRV_DEV_CLASS */

/*
 * open()
 */
static int hmcdrv_dev_open(struct inode *inode, struct file *fp)
{
	int rc;

	/* check for non-blocking access, which is really unsupported
	 */
	if (fp->f_flags & O_NONBLOCK)
		return -EINVAL;

	/* Because it makes no sense to open this device read-only (then a
	 * FTP command cannot be emitted), we respond with an error.
	 */
	if ((fp->f_flags & O_ACCMODE) == O_RDONLY)
		return -EINVAL;

	/* prevent unloading this module as long as anyone holds the
	 * device file open - so increment the reference count here
	 */
	if (!try_module_get(THIS_MODULE))
		return -ENODEV;

	fp->private_data = NULL; /* no command yet */
	rc = hmcdrv_ftp_startup();
	if (rc)
		module_put(THIS_MODULE);

	pr_debug("open file '/dev/%pD' with return code %d\n", fp, rc);
	return rc;
}

/*
 * release()
 */
static int hmcdrv_dev_release(struct inode *inode, struct file *fp)
{
	pr_debug("closing file '/dev/%pD'\n", fp);
	kfree(fp->private_data);
	fp->private_data = NULL;
	hmcdrv_ftp_shutdown();
	module_put(THIS_MODULE);
	return 0;
}

/*
 * lseek()
 */
static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence)
{
	switch (whence) {
	case SEEK_CUR: /* relative to current file position */
		pos += fp->f_pos; /* new position stored in 'pos' */
		break;

	case SEEK_SET: /* absolute (relative to beginning of file) */
		break; /* SEEK_SET */

		/* We use SEEK_END as a special indicator for a SEEK_SET
		 * (set absolute position), combined with a FTP command
		 * clear.
		 */
	case SEEK_END:
		if (fp->private_data) {
			kfree(fp->private_data);
			fp->private_data = NULL;
		}

		break; /* SEEK_END */

	default: /* SEEK_DATA, SEEK_HOLE: unsupported */
		return -EINVAL;
	}

	if (pos < 0)
		return -EINVAL;

	if (fp->f_pos != pos)
		++fp->f_version;

	fp->f_pos = pos;
	return pos;
}

/*
 * transfer (helper function)
 */
static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
				   char __user *buf, size_t len)
{
	ssize_t retlen;
	unsigned trials = HMCDRV_DEV_BUSY_RETRIES;

	do {
		retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);

		if (retlen != -EBUSY)
			break;

		msleep(HMCDRV_DEV_BUSY_DELAY);

	} while (--trials > 0);

	return retlen;
}

/*
 * read()
 */
static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
			       size_t len, loff_t *pos)
{
	ssize_t retlen;

	if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
	    (fp->private_data == NULL)) { /* no FTP cmd defined ? */
		return -EBADF;
	}

	retlen = hmcdrv_dev_transfer((char *) fp->private_data,
				     *pos, ubuf, len);

	pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",
		 fp, (long long) *pos, retlen, len);

	if (retlen > 0)
		*pos += retlen;

	return retlen;
}

/*
 * write()
 */
static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
				size_t len, loff_t *pos)
{
	ssize_t retlen;

	pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",
		 fp, (long long) *pos, len);

	if (!fp->private_data) { /* first expect a cmd write */
		fp->private_data = kmalloc(len + 1, GFP_KERNEL);

		if (!fp->private_data)
			return -ENOMEM;

		if (!copy_from_user(fp->private_data, ubuf, len)) {
			((char *)fp->private_data)[len] = '\0';
			return len;
		}

		kfree(fp->private_data);
		fp->private_data = NULL;
		return -EFAULT;
	}

	retlen = hmcdrv_dev_transfer((char *) fp->private_data,
				     *pos, (char __user *) ubuf, len);
	if (retlen > 0)
		*pos += retlen;

	pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);

	return retlen;
}

/**
 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device
 *
 * This function creates a HMC drive CD/DVD kernel device and an associated
 * device under /dev, using a dynamically allocated major number.
 *
 * Return: 0 on success, else an error code.
 */
int hmcdrv_dev_init(void)
{
	int rc;

#ifdef HMCDRV_DEV_CLASS
	struct device *dev;

	rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);

	if (rc)
		goto out_err;

	cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
	hmcdrv_dev.dev.owner = THIS_MODULE;
	rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);

	if (rc)
		goto out_unreg;

	/* At this point the character device exists in the kernel (see
	 * /proc/devices), but not under /dev nor /sys/devices/virtual. So
	 * we have to create an associated class (see /sys/class).
	 */
	hmcdrv_dev_class = class_create(THIS_MODULE, HMCDRV_DEV_CLASS);

	if (IS_ERR(hmcdrv_dev_class)) {
		rc = PTR_ERR(hmcdrv_dev_class);
		goto out_devdel;
	}

	/* Finally a device node in /dev has to be established (as 'mkdev'
	 * does from the command line). Notice that assignment of a device
	 * node name/mode function is optional (only for mode != 0600).
	 */
	hmcdrv_dev.mode = 0; /* "unset" */
	hmcdrv_dev_class->devnode = hmcdrv_dev_name;

	dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
			    "%s", HMCDRV_DEV_NAME);
	if (!IS_ERR(dev))
		return 0;

	rc = PTR_ERR(dev);
	class_destroy(hmcdrv_dev_class);
	hmcdrv_dev_class = NULL;

out_devdel:
	cdev_del(&hmcdrv_dev.dev);

out_unreg:
	unregister_chrdev_region(hmcdrv_dev_no, 1);

out_err:

#else  /* !HMCDRV_DEV_CLASS */
	hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
	hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
	hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
	hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
	rc = misc_register(&hmcdrv_dev.dev);
#endif	/* HMCDRV_DEV_CLASS */

	return rc;
}

/**
 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
 */
void hmcdrv_dev_exit(void)
{
#ifdef HMCDRV_DEV_CLASS
	if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
		device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
		class_destroy(hmcdrv_dev_class);
	}

	cdev_del(&hmcdrv_dev.dev);
	unregister_chrdev_region(hmcdrv_dev_no, 1);
#else  /* !HMCDRV_DEV_CLASS */
	misc_deregister(&hmcdrv_dev.dev);
#endif	/* HMCDRV_DEV_CLASS */
}