drivers/s390/char/hmcdrv_dev.c

   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         fp->f_pos = pos;
 190         return pos;
 191 }
 192
 193 /*
 194  * transfer (helper function)
 195  */
 196 static ssize_t hmcdrv_dev_transfer(char __kernel *cmd, loff_t offset,
 197                                    char __user *buf, size_t len)
 198 {
 199         ssize_t retlen;
 200         unsigned trials = HMCDRV_DEV_BUSY_RETRIES;
 201
 202         do {
 203                 retlen = hmcdrv_ftp_cmd(cmd, offset, buf, len);
 204
 205                 if (retlen != -EBUSY)
 206                         break;
 207
 208                 msleep(HMCDRV_DEV_BUSY_DELAY);
 209
 210         } while (--trials > 0);
 211
 212         return retlen;
 213 }
 214
 215 /*
 216  * read()
 217  */
 218 static ssize_t hmcdrv_dev_read(struct file *fp, char __user *ubuf,
 219                                size_t len, loff_t *pos)
 220 {
 221         ssize_t retlen;
 222
 223         if (((fp->f_flags & O_ACCMODE) == O_WRONLY) ||
 224             (fp->private_data == NULL)) { /* no FTP cmd defined ? */
 225                 return -EBADF;
 226         }
 227
 228         retlen = hmcdrv_dev_transfer((char *) fp->private_data,
 229                                      *pos, ubuf, len);
 230
 231         pr_debug("read from file '/dev/%pD' at %lld returns %zd/%zu\n",
 232                  fp, (long long) *pos, retlen, len);
 233
 234         if (retlen > 0)
 235                 *pos += retlen;
 236
 237         return retlen;
 238 }
 239
 240 /*
 241  * write()
 242  */
 243 static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
 244                                 size_t len, loff_t *pos)
 245 {
 246         ssize_t retlen;
 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                 fp->private_data = kmalloc(len + 1, GFP_KERNEL);
 253
 254                 if (!fp->private_data)
 255                         return -ENOMEM;
 256
 257                 if (!copy_from_user(fp->private_data, ubuf, len)) {
 258                         ((char *)fp->private_data)[len] = '\0';
 259                         return len;
 260                 }
 261
 262                 kfree(fp->private_data);
 263                 fp->private_data = NULL;
 264                 return -EFAULT;
 265         }
 266
 267         retlen = hmcdrv_dev_transfer((char *) fp->private_data,
 268                                      *pos, (char __user *) ubuf, len);
 269         if (retlen > 0)
 270                 *pos += retlen;
 271
 272         pr_debug("write to file '/dev/%pD' returned %zd\n", fp, retlen);
 273
 274         return retlen;
 275 }
 276
 277 /**
 278  * hmcdrv_dev_init() - creates a HMC drive CD/DVD device
 279  *
 280  * This function creates a HMC drive CD/DVD kernel device and an associated
 281  * device under /dev, using a dynamically allocated major number.
 282  *
 283  * Return: 0 on success, else an error code.
 284  */
 285 int hmcdrv_dev_init(void)
 286 {
 287         int rc;
 288
 289 #ifdef HMCDRV_DEV_CLASS
 290         struct device *dev;
 291
 292         rc = alloc_chrdev_region(&hmcdrv_dev_no, 0, 1, HMCDRV_DEV_NAME);
 293
 294         if (rc)
 295                 goto out_err;
 296
 297         cdev_init(&hmcdrv_dev.dev, &hmcdrv_dev_fops);
 298         hmcdrv_dev.dev.owner = THIS_MODULE;
 299         rc = cdev_add(&hmcdrv_dev.dev, hmcdrv_dev_no, 1);
 300
 301         if (rc)
 302                 goto out_unreg;
 303
 304         /* At this point the character device exists in the kernel (see
 305          * /proc/devices), but not under /dev nor /sys/devices/virtual. So
 306          * we have to create an associated class (see /sys/class).
 307          */
 308         hmcdrv_dev_class = class_create(HMCDRV_DEV_CLASS);
 309
 310         if (IS_ERR(hmcdrv_dev_class)) {
 311                 rc = PTR_ERR(hmcdrv_dev_class);
 312                 goto out_devdel;
 313         }
 314
 315         /* Finally a device node in /dev has to be established (as 'mkdev'
 316          * does from the command line). Notice that assignment of a device
 317          * node name/mode function is optional (only for mode != 0600).
 318          */
 319         hmcdrv_dev.mode = 0; /* "unset" */
 320         hmcdrv_dev_class->devnode = hmcdrv_dev_name;
 321
 322         dev = device_create(hmcdrv_dev_class, NULL, hmcdrv_dev_no, NULL,
 323                             "%s", HMCDRV_DEV_NAME);
 324         if (!IS_ERR(dev))
 325                 return 0;
 326
 327         rc = PTR_ERR(dev);
 328         class_destroy(hmcdrv_dev_class);
 329         hmcdrv_dev_class = NULL;
 330
 331 out_devdel:
 332         cdev_del(&hmcdrv_dev.dev);
 333
 334 out_unreg:
 335         unregister_chrdev_region(hmcdrv_dev_no, 1);
 336
 337 out_err:
 338
 339 #else  /* !HMCDRV_DEV_CLASS */
 340         hmcdrv_dev.dev.minor = MISC_DYNAMIC_MINOR;
 341         hmcdrv_dev.dev.name = HMCDRV_DEV_NAME;
 342         hmcdrv_dev.dev.fops = &hmcdrv_dev_fops;
 343         hmcdrv_dev.dev.mode = 0; /* finally produces 0600 */
 344         rc = misc_register(&hmcdrv_dev.dev);
 345 #endif  /* HMCDRV_DEV_CLASS */
 346
 347         return rc;
 348 }
 349
 350 /**
 351  * hmcdrv_dev_exit() - destroys a HMC drive CD/DVD device
 352  */
 353 void hmcdrv_dev_exit(void)
 354 {
 355 #ifdef HMCDRV_DEV_CLASS
 356         if (!IS_ERR_OR_NULL(hmcdrv_dev_class)) {
 357                 device_destroy(hmcdrv_dev_class, hmcdrv_dev_no);
 358                 class_destroy(hmcdrv_dev_class);
 359         }
 360
 361         cdev_del(&hmcdrv_dev.dev);
 362         unregister_chrdev_region(hmcdrv_dev_no, 1);
 363 #else  /* !HMCDRV_DEV_CLASS */
 364         misc_deregister(&hmcdrv_dev.dev);
 365 #endif  /* HMCDRV_DEV_CLASS */
 366 }