1// SPDX-License-Identifier: GPL-2.0
2/*
3 * HMC Drive CD/DVD Device
4 *
5 * Copyright IBM Corp. 2013
6 * Author(s): Ralf Hoppe (rhoppe@de.ibm.com)
7 *
8 * This file provides a Linux "misc" character device for access to an
9 * assigned HMC drive CD/DVD-ROM. It works as follows: First create the
10 * device by calling hmcdrv_dev_init(). After open() a lseek(fd, 0,
11 * SEEK_END) indicates that a new FTP command follows (not needed on the
12 * first command after open). Then write() the FTP command ASCII string
13 * to it, e.g. "dir /" or "nls <directory>" or "get <filename>". At the
14 * end read() the response.
15 */
16
17#define pr_fmt(fmt) "hmcdrv: " 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(const 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(objp: 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(objp: 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 fp->f_pos = pos;
189 return pos;
190}
191
192/*
193 * transfer (helper function)
194 */
195static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
196 char __user *buf, size_t len)
197{
198 ssize_t retlen;
199 unsigned trials = HMCDRV_DEV_BUSY_RETRIES;
200
201 do {
202 retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);
203
204 if (retlen != -EBUSY)
205 break;
206
207 msleep(HMCDRV_DEV_BUSY_DELAY);
208
209 } while (--trials > 0);
210
211 return retlen;
212}
213
214/*
215 * read()
216 */
217static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
218 size_t len, loff_t *pos)
219{
220 ssize_t retlen;
221
222 if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
223 (fp->private_data == NULL)) { /* no FTP cmd defined ? */
224 return -EBADF;
225 }
226
227 retlen = hmcdrv_dev_transfer(cmd: (char *) fp->private_data,
228 offset: *pos, buf: ubuf, len);
229
230 pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",
231 fp, (long long) *pos, retlen, len);
232
233 if (retlen > 0)
234 *pos += retlen;
235
236 return retlen;
237}
238
239/*
240 * write()
241 */
242static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
243 size_t len, loff_t *pos)
244{
245 ssize_t retlen;
246 void *pdata;
247
248 pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",
249 fp, (long long) *pos, len);
250
251 if (!fp->private_data) { /* first expect a cmd write */
252 pdata = memdup_user_nul(ubuf, len);
253 if (IS_ERR(ptr: pdata))
254 return PTR_ERR(ptr: pdata);
255 fp->private_data = pdata;
256 return len;
257 }
258
259 retlen = hmcdrv_dev_transfer(cmd: (char *) fp->private_data,
260 offset: *pos, buf: (char __user *) ubuf, len);
261 if (retlen > 0)
262 *pos += retlen;
263
264 pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);
265
266 return retlen;
267}
268
269/**
270 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device
271 *
272 * This function creates a HMC drive CD/DVD kernel device and an associated
273 * device under /dev, using a dynamically allocated major number.
274 *
275 * Return: 0 on success, else an error code.
276 */
277int hmcdrv_dev_init(void)
278{
279 int rc;
280
281#ifdef HMCDRV_DEV_CLASS
282 struct device *dev;
283
284 rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);
285
286 if (rc)
287 goto out_err;
288
289 cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
290 hmcdrv_dev.dev.owner = THIS_MODULE;
291 rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);
292
293 if (rc)
294 goto out_unreg;
295
296 /* At this point the character device exists in the kernel (see
297 * /proc/devices), but not under /dev nor /sys/devices/virtual. So
298 * we have to create an associated class (see /sys/class).
299 */
300 hmcdrv_dev_class = class_create(HMCDRV_DEV_CLASS);
301
302 if (IS_ERR(hmcdrv_dev_class)) {
303 rc = PTR_ERR(hmcdrv_dev_class);
304 goto out_devdel;
305 }
306
307 /* Finally a device node in /dev has to be established (as 'mkdev'
308 * does from the command line). Notice that assignment of a device
309 * node name/mode function is optional (only for mode != 0600).
310 */
311 hmcdrv_dev.mode = 0; /* "unset" */
312 hmcdrv_dev_class->devnode = hmcdrv_dev_name;
313
314 dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
315 "%s", HMCDRV_DEV_NAME);
316 if (!IS_ERR(dev))
317 return 0;
318
319 rc = PTR_ERR(dev);
320 class_destroy(hmcdrv_dev_class);
321 hmcdrv_dev_class = NULL;
322
323out_devdel:
324 cdev_del(&hmcdrv_dev.dev);
325
326out_unreg:
327 unregister_chrdev_region(hmcdrv_dev_no, 1);
328
329out_err:
330
331#else /* !HMCDRV_DEV_CLASS */
332 hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
333 hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
334 hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
335 hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
336 rc = misc_register(misc: &hmcdrv_dev.dev);
337#endif /* HMCDRV_DEV_CLASS */
338
339 return rc;
340}
341
342/**
343 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
344 */
345void hmcdrv_dev_exit(void)
346{
347#ifdef HMCDRV_DEV_CLASS
348 if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
349 device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
350 class_destroy(hmcdrv_dev_class);
351 }
352
353 cdev_del(&hmcdrv_dev.dev);
354 unregister_chrdev_region(hmcdrv_dev_no, 1);
355#else /* !HMCDRV_DEV_CLASS */
356 misc_deregister(misc: &hmcdrv_dev.dev);
357#endif /* HMCDRV_DEV_CLASS */
358}
359

source code of linux/drivers/s390/char/hmcdrv_dev.c