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 KMSG_COMPONENT "hmcdrv" 18 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt 19 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/slab.h> 23 #include <linux/fs.h> 24 #include <linux/cdev.h> 25 #include <linux/miscdevice.h> 26 #include <linux/device.h> 27 #include <linux/capability.h> 28 #include <linux/delay.h> 29 #include <linux/uaccess.h> 30 31 #include "hmcdrv_dev.h" 32 #include "hmcdrv_ftp.h" 33 34 /* If the following macro is defined, then the HMC device creates it's own 35 * separated device class (and dynamically assigns a major number). If not 36 * defined then the HMC device is assigned to the "misc" class devices. 37 * 38 #define HMCDRV_DEV_CLASS "hmcftp" 39 */ 40 41 #define HMCDRV_DEV_NAME "hmcdrv" 42 #define HMCDRV_DEV_BUSY_DELAY 500 /* delay between -EBUSY trials in ms */ 43 #define HMCDRV_DEV_BUSY_RETRIES 3 /* number of retries on -EBUSY */ 44 45 struct hmcdrv_dev_node { 46 47 #ifdef HMCDRV_DEV_CLASS 48 struct cdev dev; /* character device structure */ 49 umode_t mode; /* mode of device node (unused, zero) */ 50 #else 51 struct miscdevice dev; /* "misc" device structure */ 52 #endif 53 54 }; 55 56 static int hmcdrv_dev_open(struct inode *inode, struct file *fp); 57 static int hmcdrv_dev_release(struct inode *inode, struct file *fp); 58 static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence); 59 static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf, 60 size_t len, loff_t *pos); 61 static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf, 62 size_t len, loff_t *pos); 63 static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset, 64 char __user *buf, size_t len); 65 66 /* 67 * device operations 68 */ 69 static const struct file_operations hmcdrv_dev_fops = { 70 .open = hmcdrv_dev_open, 71 .llseek = hmcdrv_dev_seek, 72 .release = hmcdrv_dev_release, 73 .read = hmcdrv_dev_read, 74 .write = hmcdrv_dev_write, 75 }; 76 77 static struct hmcdrv_dev_node hmcdrv_dev; /* HMC device struct (static) */ 78 79 #ifdef HMCDRV_DEV_CLASS 80 81 static struct class *hmcdrv_dev_class; /* device class pointer */ 82 static dev_t hmcdrv_dev_no; /* device number (major/minor) */ 83 84 /** 85 * hmcdrv_dev_name() - provides a naming hint for a device node in /dev 86 * @dev: device for which the naming/mode hint is 87 * @mode: file mode for device node created in /dev 88 * 89 * See: devtmpfs.c, function devtmpfs_create_node() 90 * 91 * Return: recommended device file name in /dev 92 */ 93 static char *hmcdrv_dev_name(const struct device *dev, umode_t *mode) 94 { 95 char *nodename = NULL; 96 const char *devname = dev_name(dev); /* kernel device name */ 97 98 if (devname) 99 nodename = kasprintf(GFP_KERNEL, "%s", devname); 100 101 /* on device destroy (rmmod) the mode pointer may be NULL 102 */ 103 if (mode) 104 *mode = hmcdrv_dev.mode; 105 106 return nodename; 107 } 108 109 #endif /* HMCDRV_DEV_CLASS */ 110 111 /* 112 * open() 113 */ 114 static int hmcdrv_dev_open(struct inode *inode, struct file *fp) 115 { 116 int rc; 117 118 /* check for non-blocking access, which is really unsupported 119 */ 120 if (fp->f_flags & O_NONBLOCK) 121 return -EINVAL; 122 123 /* Because it makes no sense to open this device read-only (then a 124 * FTP command cannot be emitted), we respond with an error. 125 */ 126 if ((fp->f_flags & O_ACCMODE) == O_RDONLY) 127 return -EINVAL; 128 129 /* prevent unloading this module as long as anyone holds the 130 * device file open - so increment the reference count here 131 */ 132 if (!try_module_get(THIS_MODULE)) 133 return -ENODEV; 134 135 fp->private_data = NULL; /* no command yet */ 136 rc = hmcdrv_ftp_startup(); 137 if (rc) 138 module_put(THIS_MODULE); 139 140 pr_debug("open file '/dev/%pD' with return code %d\n", fp, rc); 141 return rc; 142 } 143 144 /* 145 * release() 146 */ 147 static int hmcdrv_dev_release(struct inode *inode, struct file *fp) 148 { 149 pr_debug("closing file '/dev/%pD'\n", fp); 150 kfree(fp->private_data); 151 fp->private_data = NULL; 152 hmcdrv_ftp_shutdown(); 153 module_put(THIS_MODULE); 154 return 0; 155 } 156 157 /* 158 * lseek() 159 */ 160 static loff_t hmcdrv_dev_seek(struct file *fp, loff_t pos, int whence) 161 { 162 switch (whence) { 163 case SEEK_CUR: /* relative to current file position */ 164 pos += fp->f_pos; /* new position stored in 'pos' */ 165 break; 166 167 case SEEK_SET: /* absolute (relative to beginning of file) */ 168 break; /* SEEK_SET */ 169 170 /* We use SEEK_END as a special indicator for a SEEK_SET 171 * (set absolute position), combined with a FTP command 172 * clear. 173 */ 174 case SEEK_END: 175 if (fp->private_data) { 176 kfree(fp->private_data); 177 fp->private_data = NULL; 178 } 179 180 break; /* SEEK_END */ 181 182 default: /* SEEK_DATA, SEEK_HOLE: unsupported */ 183 return -EINVAL; 184 } 185 186 if (pos < 0) 187 return -EINVAL; 188 189 if (fp->f_pos != pos) 190 ++fp->f_version; 191 192 fp->f_pos = pos; 193 return pos; 194 } 195 196 /* 197 * transfer (helper function) 198 */ 199 static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset, 200 char __user *buf, size_t len) 201 { 202 ssize_t retlen; 203 unsigned trials = HMCDRV_DEV_BUSY_RETRIES; 204 205 do { 206 retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len); 207 208 if (retlen != -EBUSY) 209 break; 210 211 msleep(HMCDRV_DEV_BUSY_DELAY); 212 213 } while (--trials > 0); 214 215 return retlen; 216 } 217 218 /* 219 * read() 220 */ 221 static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf, 222 size_t len, loff_t *pos) 223 { 224 ssize_t retlen; 225 226 if (((fp->f_flags & O_ACCMODE) == O_WRONLY) || 227 (fp->private_data == NULL)) { /* no FTP cmd defined ? */ 228 return -EBADF; 229 } 230 231 retlen = hmcdrv_dev_transfer((char *) fp->private_data, 232 *pos, ubuf, len); 233 234 pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n", 235 fp, (long long) *pos, retlen, len); 236 237 if (retlen > 0) 238 *pos += retlen; 239 240 return retlen; 241 } 242 243 /* 244 * write() 245 */ 246 static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf, 247 size_t len, loff_t *pos) 248 { 249 ssize_t retlen; 250 251 pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n", 252 fp, (long long) *pos, len); 253 254 if (!fp->private_data) { /* first expect a cmd write */ 255 fp->private_data = kmalloc(len + 1, GFP_KERNEL); 256 257 if (!fp->private_data) 258 return -ENOMEM; 259 260 if (!copy_from_user(fp->private_data, ubuf, len)) { 261 ((char *)fp->private_data)[len] = '\0'; 262 return len; 263 } 264 265 kfree(fp->private_data); 266 fp->private_data = NULL; 267 return -EFAULT; 268 } 269 270 retlen = hmcdrv_dev_transfer((char *) fp->private_data, 271 *pos, (char __user *) ubuf, len); 272 if (retlen > 0) 273 *pos += retlen; 274 275 pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen); 276 277 return retlen; 278 } 279 280 /** 281 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device 282 * 283 * This function creates a HMC drive CD/DVD kernel device and an associated 284 * device under /dev, using a dynamically allocated major number. 285 * 286 * Return: 0 on success, else an error code. 287 */ 288 int hmcdrv_dev_init(void) 289 { 290 int rc; 291 292 #ifdef HMCDRV_DEV_CLASS 293 struct device *dev; 294 295 rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME); 296 297 if (rc) 298 goto out_err; 299 300 cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops); 301 hmcdrv_dev.dev.owner = THIS_MODULE; 302 rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1); 303 304 if (rc) 305 goto out_unreg; 306 307 /* At this point the character device exists in the kernel (see 308 * /proc/devices), but not under /dev nor /sys/devices/virtual. So 309 * we have to create an associated class (see /sys/class). 310 */ 311 hmcdrv_dev_class = class_create(HMCDRV_DEV_CLASS); 312 313 if (IS_ERR(hmcdrv_dev_class)) { 314 rc = PTR_ERR(hmcdrv_dev_class); 315 goto out_devdel; 316 } 317 318 /* Finally a device node in /dev has to be established (as 'mkdev' 319 * does from the command line). Notice that assignment of a device 320 * node name/mode function is optional (only for mode != 0600). 321 */ 322 hmcdrv_dev.mode = 0; /* "unset" */ 323 hmcdrv_dev_class->devnode = hmcdrv_dev_name; 324 325 dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL, 326 "%s", HMCDRV_DEV_NAME); 327 if (!IS_ERR(dev)) 328 return 0; 329 330 rc = PTR_ERR(dev); 331 class_destroy(hmcdrv_dev_class); 332 hmcdrv_dev_class = NULL; 333 334 out_devdel: 335 cdev_del(&hmcdrv_dev.dev); 336 337 out_unreg: 338 unregister_chrdev_region(hmcdrv_dev_no, 1); 339 340 out_err: 341 342 #else /* !HMCDRV_DEV_CLASS */ 343 hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR; 344 hmcdrv_dev.dev.name = HMCDRV_DEV_NAME; 345 hmcdrv_dev.dev.fops = &hmcdrv_dev_fops; 346 hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */ 347 rc = misc_register(&hmcdrv_dev.dev); 348 #endif /* HMCDRV_DEV_CLASS */ 349 350 return rc; 351 } 352 353 /** 354 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device 355 */ 356 void hmcdrv_dev_exit(void) 357 { 358 #ifdef HMCDRV_DEV_CLASS 359 if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) { 360 device_destroy(hmcdrv_dev_class, hmcdrv_dev_no); 361 class_destroy(hmcdrv_dev_class); 362 } 363 364 cdev_del(&hmcdrv_dev.dev); 365 unregister_chrdev_region(hmcdrv_dev_no, 1); 366 #else /* !HMCDRV_DEV_CLASS */ 367 misc_deregister(&hmcdrv_dev.dev); 368 #endif /* HMCDRV_DEV_CLASS */ 369 } 370