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/%s' with return code %d\n", 140 fp->f_dentry->d_name.name, rc); 141 return rc; 142} 143 144/* 145 * release() 146 */ 147static int hmcdrv_dev_release(struct inode *inode, struct file *fp) 148{ 149 pr_debug("closing file '/dev/%s'\n", fp->f_dentry->d_name.name); 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 */ 160static 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 */ 199static 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 */ 221static 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/%s' at %lld returns %zd/%zu\n", 235 fp->f_dentry->d_name.name, (long long) *pos, retlen, len); 236 237 if (retlen > 0) 238 *pos += retlen; 239 240 return retlen; 241} 242 243/* 244 * write() 245 */ 246static 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/%s' at pos. %lld with length %zd\n", 252 fp->f_dentry->d_name.name, (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/%s' returned %zd\n", 276 fp->f_dentry->d_name.name, retlen); 277 278 return retlen; 279} 280 281/** 282 * hmcdrv_dev_init() - creates a HMC drive CD/DVD device 283 * 284 * This function creates a HMC drive CD/DVD kernel device and an associated 285 * device under /dev, using a dynamically allocated major number. 286 * 287 * Return: 0 on success, else an error code. 288 */ 289int hmcdrv_dev_init(void) 290{ 291 int rc; 292 293#ifdef HMCDRV_DEV_CLASS 294 struct device *dev; 295 296 rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME); 297 298 if (rc) 299 goto out_err; 300 301 cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops); 302 hmcdrv_dev.dev.owner = THIS_MODULE; 303 rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1); 304 305 if (rc) 306 goto out_unreg; 307 308 /* At this point the character device exists in the kernel (see 309 * /proc/devices), but not under /dev nor /sys/devices/virtual. So 310 * we have to create an associated class (see /sys/class). 311 */ 312 hmcdrv_dev_class = class_create(THIS_MODULE, HMCDRV_DEV_CLASS); 313 314 if (IS_ERR(hmcdrv_dev_class)) { 315 rc = PTR_ERR(hmcdrv_dev_class); 316 goto out_devdel; 317 } 318 319 /* Finally a device node in /dev has to be established (as 'mkdev' 320 * does from the command line). Notice that assignment of a device 321 * node name/mode function is optional (only for mode != 0600). 322 */ 323 hmcdrv_dev.mode = 0; /* "unset" */ 324 hmcdrv_dev_class->devnode = hmcdrv_dev_name; 325 326 dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL, 327 "%s", HMCDRV_DEV_NAME); 328 if (!IS_ERR(dev)) 329 return 0; 330 331 rc = PTR_ERR(dev); 332 class_destroy(hmcdrv_dev_class); 333 hmcdrv_dev_class = NULL; 334 335out_devdel: 336 cdev_del(&hmcdrv_dev.dev); 337 338out_unreg: 339 unregister_chrdev_region(hmcdrv_dev_no, 1); 340 341out_err: 342 343#else /* !HMCDRV_DEV_CLASS */ 344 hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR; 345 hmcdrv_dev.dev.name = HMCDRV_DEV_NAME; 346 hmcdrv_dev.dev.fops = &hmcdrv_dev_fops; 347 hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */ 348 rc = misc_register(&hmcdrv_dev.dev); 349#endif /* HMCDRV_DEV_CLASS */ 350 351 return rc; 352} 353 354/** 355 * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device 356 */ 357void hmcdrv_dev_exit(void) 358{ 359#ifdef HMCDRV_DEV_CLASS 360 if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) { 361 device_destroy(hmcdrv_dev_class, hmcdrv_dev_no); 362 class_destroy(hmcdrv_dev_class); 363 } 364 365 cdev_del(&hmcdrv_dev.dev); 366 unregister_chrdev_region(hmcdrv_dev_no, 1); 367#else /* !HMCDRV_DEV_CLASS */ 368 misc_deregister(&hmcdrv_dev.dev); 369#endif /* HMCDRV_DEV_CLASS */ 370} 371