drivers/char/mem.c

   1 /*
   2  *  linux/drivers/char/mem.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  *
   6  *  Added devfs support.
   7  *    Jan-11-1998, C. Scott Ananian <cananian@alumni.princeton.edu>
   8  *  Shared /dev/zero mmaping support, Feb 2000, Kanoj Sarcar <kanoj@sgi.com>
   9  */
  10
  11 #include <linux/config.h>
  12 #include <linux/mm.h>
  13 #include <linux/miscdevice.h>
  14 #include <linux/slab.h>
  15 #include <linux/vmalloc.h>
  16 #include <linux/mman.h>
  17 #include <linux/random.h>
  18 #include <linux/init.h>
  19 #include <linux/raw.h>
  20 #include <linux/tty.h>
  21 #include <linux/capability.h>
  22 #include <linux/smp_lock.h>
  23 #include <linux/devfs_fs_kernel.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/device.h>
  26
  27 #include <asm/uaccess.h>
  28 #include <asm/io.h>
  29
  30 #ifdef CONFIG_IA64
  31 # include <linux/efi.h>
  32 #endif
  33
  34 #if defined(CONFIG_S390_TAPE) && defined(CONFIG_S390_TAPE_CHAR)
  35 extern void tapechar_init(void);
  36 #endif
  37
  38 /*
  39  * Architectures vary in how they handle caching for addresses
  40  * outside of main memory.
  41  *
  42  */
  43 static inline int uncached_access(struct file *file, unsigned long addr)
  44 {
  45 #if defined(__i386__)
  46         /*
  47          * On the PPro and successors, the MTRRs are used to set
  48          * memory types for physical addresses outside main memory,
  49          * so blindly setting PCD or PWT on those pages is wrong.
  50          * For Pentiums and earlier, the surround logic should disable
  51          * caching for the high addresses through the KEN pin, but
  52          * we maintain the tradition of paranoia in this code.
  53          */
  54         if (file->f_flags & O_SYNC)
  55                 return 1;
  56         return !( test_bit(X86_FEATURE_MTRR, boot_cpu_data.x86_capability) ||
  57                   test_bit(X86_FEATURE_K6_MTRR, boot_cpu_data.x86_capability) ||
  58                   test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
  59                   test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability) )
  60           && addr >= __pa(high_memory);
  61 #elif defined(__x86_64__)
  62         /*
  63          * This is broken because it can generate memory type aliases,
  64          * which can cause cache corruptions
  65          * But it is only available for root and we have to be bug-to-bug
  66          * compatible with i386.
  67          */
  68         if (file->f_flags & O_SYNC)
  69                 return 1;
  70         /* same behaviour as i386. PAT always set to cached and MTRRs control the
  71            caching behaviour.
  72            Hopefully a full PAT implementation will fix that soon. */
  73         return 0;
  74 #elif defined(CONFIG_IA64)
  75         /*
  76          * On ia64, we ignore O_SYNC because we cannot tolerate memory attribute aliases.
  77          */
  78         return !(efi_mem_attributes(addr) & EFI_MEMORY_WB);
  79 #elif defined(CONFIG_PPC64)
  80         /* On PPC64, we always do non-cacheable access to the IO hole and
  81          * cacheable elsewhere. Cache paradox can checkstop the CPU and
  82          * the high_memory heuristic below is wrong on machines with memory
  83          * above the IO hole... Ah, and of course, XFree86 doesn't pass
  84          * O_SYNC when mapping us to tap IO space. Surprised ?
  85          */
  86         return !page_is_ram(addr >> PAGE_SHIFT);
  87 #else
  88         /*
  89          * Accessing memory above the top the kernel knows about or through a file pointer
  90          * that was marked O_SYNC will be done non-cached.
  91          */
  92         if (file->f_flags & O_SYNC)
  93                 return 1;
  94         return addr >= __pa(high_memory);
  95 #endif
  96 }
  97
  98 #ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE
  99 static inline int valid_phys_addr_range(unsigned long addr, size_t *count)
 100 {
 101         unsigned long end_mem;
 102
 103         end_mem = __pa(high_memory);
 104         if (addr >= end_mem)
 105                 return 0;
 106
 107         if (*count > end_mem - addr)
 108                 *count = end_mem - addr;
 109
 110         return 1;
 111 }
 112 #endif
 113
 114 static ssize_t do_write_mem(void *p, unsigned long realp,
 115                             const char __user * buf, size_t count, loff_t *ppos)
 116 {
 117         ssize_t written;
 118         unsigned long copied;
 119
 120         written = 0;
 121 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 122         /* we don't have page 0 mapped on sparc and m68k.. */
 123         if (realp < PAGE_SIZE) {
 124                 unsigned long sz = PAGE_SIZE-realp;
 125                 if (sz > count) sz = count;
 126                 /* Hmm. Do something? */
 127                 buf+=sz;
 128                 p+=sz;
 129                 count-=sz;
 130                 written+=sz;
 131         }
 132 #endif
 133         copied = copy_from_user(p, buf, count);
 134         if (copied) {
 135                 ssize_t ret = written + (count - copied);
 136
 137                 if (ret)
 138                         return ret;
 139                 return -EFAULT;
 140         }
 141         written += count;
 142         *ppos += written;
 143         return written;
 144 }
 145
 146
 147 /*
 148  * This funcion reads the *physical* memory. The f_pos points directly to the
 149  * memory location.
 150  */
 151 static ssize_t read_mem(struct file * file, char __user * buf,
 152                         size_t count, loff_t *ppos)
 153 {
 154         unsigned long p = *ppos;
 155         ssize_t read;
 156
 157         if (!valid_phys_addr_range(p, &count))
 158                 return -EFAULT;
 159         read = 0;
 160 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 161         /* we don't have page 0 mapped on sparc and m68k.. */
 162         if (p < PAGE_SIZE) {
 163                 unsigned long sz = PAGE_SIZE-p;
 164                 if (sz > count)
 165                         sz = count;
 166                 if (sz > 0) {
 167                         if (clear_user(buf, sz))
 168                                 return -EFAULT;
 169                         buf += sz;
 170                         p += sz;
 171                         count -= sz;
 172                         read += sz;
 173                 }
 174         }
 175 #endif
 176         if (copy_to_user(buf, __va(p), count))
 177                 return -EFAULT;
 178         read += count;
 179         *ppos += read;
 180         return read;
 181 }
 182
 183 static ssize_t write_mem(struct file * file, const char __user * buf,
 184                          size_t count, loff_t *ppos)
 185 {
 186         unsigned long p = *ppos;
 187
 188         if (!valid_phys_addr_range(p, &count))
 189                 return -EFAULT;
 190         return do_write_mem(__va(p), p, buf, count, ppos);
 191 }
 192
 193 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 194 {
 195         unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
 196         int uncached;
 197
 198         uncached = uncached_access(file, offset);
 199 #ifdef pgprot_noncached
 200         if (uncached)
 201                 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 202 #endif
 203
 204         /* Don't try to swap out physical pages.. */
 205         vma->vm_flags |= VM_RESERVED;
 206
 207         /*
 208          * Don't dump addresses that are not real memory to a core file.
 209          */
 210         if (uncached)
 211                 vma->vm_flags |= VM_IO;
 212
 213         if (remap_page_range(vma, vma->vm_start, offset, vma->vm_end-vma->vm_start,
 214                              vma->vm_page_prot))
 215                 return -EAGAIN;
 216         return 0;
 217 }
 218
 219 extern long vread(char *buf, char *addr, unsigned long count);
 220 extern long vwrite(char *buf, char *addr, unsigned long count);
 221
 222 /*
 223  * This function reads the *virtual* memory as seen by the kernel.
 224  */
 225 static ssize_t read_kmem(struct file *file, char __user *buf,
 226                          size_t count, loff_t *ppos)
 227 {
 228         unsigned long p = *ppos;
 229         ssize_t read = 0;
 230         ssize_t virtr = 0;
 231         char * kbuf; /* k-addr because vread() takes vmlist_lock rwlock */
 232
 233         if (p < (unsigned long) high_memory) {
 234                 read = count;
 235                 if (count > (unsigned long) high_memory - p)
 236                         read = (unsigned long) high_memory - p;
 237
 238 #if defined(__sparc__) || (defined(__mc68000__) && defined(CONFIG_MMU))
 239                 /* we don't have page 0 mapped on sparc and m68k.. */
 240                 if (p < PAGE_SIZE && read > 0) {
 241                         size_t tmp = PAGE_SIZE - p;
 242                         if (tmp > read) tmp = read;
 243                         if (clear_user(buf, tmp))
 244                                 return -EFAULT;
 245                         buf += tmp;
 246                         p += tmp;
 247                         read -= tmp;
 248                         count -= tmp;
 249                 }
 250 #endif
 251                 if (copy_to_user(buf, (char *)p, read))
 252                         return -EFAULT;
 253                 p += read;
 254                 buf += read;
 255                 count -= read;
 256         }
 257
 258         if (count > 0) {
 259                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 260                 if (!kbuf)
 261                         return -ENOMEM;
 262                 while (count > 0) {
 263                         int len = count;
 264
 265                         if (len > PAGE_SIZE)
 266                                 len = PAGE_SIZE;
 267                         len = vread(kbuf, (char *)p, len);
 268                         if (!len)
 269                                 break;
 270                         if (copy_to_user(buf, kbuf, len)) {
 271                                 free_page((unsigned long)kbuf);
 272                                 return -EFAULT;
 273                         }
 274                         count -= len;
 275                         buf += len;
 276                         virtr += len;
 277                         p += len;
 278                 }
 279                 free_page((unsigned long)kbuf);
 280         }
 281         *ppos = p;
 282         return virtr + read;
 283 }
 284
 285 /*
 286  * This function writes to the *virtual* memory as seen by the kernel.
 287  */
 288 static ssize_t write_kmem(struct file * file, const char __user * buf,
 289                           size_t count, loff_t *ppos)
 290 {
 291         unsigned long p = *ppos;
 292         ssize_t wrote = 0;
 293         ssize_t virtr = 0;
 294         ssize_t written;
 295         char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
 296
 297         if (p < (unsigned long) high_memory) {
 298
 299                 wrote = count;
 300                 if (count > (unsigned long) high_memory - p)
 301                         wrote = (unsigned long) high_memory - p;
 302
 303                 written = do_write_mem((void*)p, p, buf, wrote, ppos);
 304                 if (written != wrote)
 305                         return written;
 306                 wrote = written;
 307                 p += wrote;
 308                 buf += wrote;
 309                 count -= wrote;
 310         }
 311
 312         if (count > 0) {
 313                 kbuf = (char *)__get_free_page(GFP_KERNEL);
 314                 if (!kbuf)
 315                         return wrote ? wrote : -ENOMEM;
 316                 while (count > 0) {
 317                         int len = count;
 318
 319                         if (len > PAGE_SIZE)
 320                                 len = PAGE_SIZE;
 321                         if (len) {
 322                                 written = copy_from_user(kbuf, buf, len);
 323                                 if (written) {
 324                                         ssize_t ret;
 325
 326                                         free_page((unsigned long)kbuf);
 327                                         ret = wrote + virtr + (len - written);
 328                                         return ret ? ret : -EFAULT;
 329                                 }
 330                         }
 331                         len = vwrite(kbuf, (char *)p, len);
 332                         count -= len;
 333                         buf += len;
 334                         virtr += len;
 335                         p += len;
 336                 }
 337                 free_page((unsigned long)kbuf);
 338         }
 339
 340         *ppos = p;
 341         return virtr + wrote;
 342 }
 343
 344 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 345 static ssize_t read_port(struct file * file, char __user * buf,
 346                          size_t count, loff_t *ppos)
 347 {
 348         unsigned long i = *ppos;
 349         char __user *tmp = buf;
 350
 351         if (verify_area(VERIFY_WRITE,buf,count))
 352                 return -EFAULT;
 353         while (count-- > 0 && i < 65536) {
 354                 if (__put_user(inb(i),tmp) < 0)
 355                         return -EFAULT;
 356                 i++;
 357                 tmp++;
 358         }
 359         *ppos = i;
 360         return tmp-buf;
 361 }
 362
 363 static ssize_t write_port(struct file * file, const char __user * buf,
 364                           size_t count, loff_t *ppos)
 365 {
 366         unsigned long i = *ppos;
 367         const char __user * tmp = buf;
 368
 369         if (verify_area(VERIFY_READ,buf,count))
 370                 return -EFAULT;
 371         while (count-- > 0 && i < 65536) {
 372                 char c;
 373                 if (__get_user(c, tmp))
 374                         return -EFAULT;
 375                 outb(c,i);
 376                 i++;
 377                 tmp++;
 378         }
 379         *ppos = i;
 380         return tmp-buf;
 381 }
 382 #endif
 383
 384 static ssize_t read_null(struct file * file, char __user * buf,
 385                          size_t count, loff_t *ppos)
 386 {
 387         return 0;
 388 }
 389
 390 static ssize_t write_null(struct file * file, const char __user * buf,
 391                           size_t count, loff_t *ppos)
 392 {
 393         return count;
 394 }
 395
 396 #ifdef CONFIG_MMU
 397 /*
 398  * For fun, we are using the MMU for this.
 399  */
 400 static inline size_t read_zero_pagealigned(char __user * buf, size_t size)
 401 {
 402         struct mm_struct *mm;
 403         struct vm_area_struct * vma;
 404         unsigned long addr=(unsigned long)buf;
 405
 406         mm = current->mm;
 407         /* Oops, this was forgotten before. -ben */
 408         down_read(&mm->mmap_sem);
 409
 410         /* For private mappings, just map in zero pages. */
 411         for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
 412                 unsigned long count;
 413
 414                 if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)
 415                         goto out_up;
 416                 if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))
 417                         break;
 418                 count = vma->vm_end - addr;
 419                 if (count > size)
 420                         count = size;
 421
 422                 zap_page_range(vma, addr, count, NULL);
 423                 zeromap_page_range(vma, addr, count, PAGE_COPY);
 424
 425                 size -= count;
 426                 buf += count;
 427                 addr += count;
 428                 if (size == 0)
 429                         goto out_up;
 430         }
 431
 432         up_read(&mm->mmap_sem);
 433
 434         /* The shared case is hard. Let's do the conventional zeroing. */
 435         do {
 436                 unsigned long unwritten = clear_user(buf, PAGE_SIZE);
 437                 if (unwritten)
 438                         return size + unwritten - PAGE_SIZE;
 439                 cond_resched();
 440                 buf += PAGE_SIZE;
 441                 size -= PAGE_SIZE;
 442         } while (size);
 443
 444         return size;
 445 out_up:
 446         up_read(&mm->mmap_sem);
 447         return size;
 448 }
 449
 450 static ssize_t read_zero(struct file * file, char __user * buf,
 451                          size_t count, loff_t *ppos)
 452 {
 453         unsigned long left, unwritten, written = 0;
 454
 455         if (!count)
 456                 return 0;
 457
 458         if (!access_ok(VERIFY_WRITE, buf, count))
 459                 return -EFAULT;
 460
 461         left = count;
 462
 463         /* do we want to be clever? Arbitrary cut-off */
 464         if (count >= PAGE_SIZE*4) {
 465                 unsigned long partial;
 466
 467                 /* How much left of the page? */
 468                 partial = (PAGE_SIZE-1) & -(unsigned long) buf;
 469                 unwritten = clear_user(buf, partial);
 470                 written = partial - unwritten;
 471                 if (unwritten)
 472                         goto out;
 473                 left -= partial;
 474                 buf += partial;
 475                 unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
 476                 written += (left & PAGE_MASK) - unwritten;
 477                 if (unwritten)
 478                         goto out;
 479                 buf += left & PAGE_MASK;
 480                 left &= ~PAGE_MASK;
 481         }
 482         unwritten = clear_user(buf, left);
 483         written += left - unwritten;
 484 out:
 485         return written ? written : -EFAULT;
 486 }
 487
 488 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 489 {
 490         if (vma->vm_flags & VM_SHARED)
 491                 return shmem_zero_setup(vma);
 492         if (zeromap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, vma->vm_page_prot))
 493                 return -EAGAIN;
 494         return 0;
 495 }
 496 #else /* CONFIG_MMU */
 497 static ssize_t read_zero(struct file * file, char * buf,
 498                          size_t count, loff_t *ppos)
 499 {
 500         size_t todo = count;
 501
 502         while (todo) {
 503                 size_t chunk = todo;
 504
 505                 if (chunk > 4096)
 506                         chunk = 4096;   /* Just for latency reasons */
 507                 if (clear_user(buf, chunk))
 508                         return -EFAULT;
 509                 buf += chunk;
 510                 todo -= chunk;
 511                 cond_resched();
 512         }
 513         return count;
 514 }
 515
 516 static int mmap_zero(struct file * file, struct vm_area_struct * vma)
 517 {
 518         return -ENOSYS;
 519 }
 520 #endif /* CONFIG_MMU */
 521
 522 static ssize_t write_full(struct file * file, const char __user * buf,
 523                           size_t count, loff_t *ppos)
 524 {
 525         return -ENOSPC;
 526 }
 527
 528 /*
 529  * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 530  * can fopen() both devices with "a" now.  This was previously impossible.
 531  * -- SRB.
 532  */
 533
 534 static loff_t null_lseek(struct file * file, loff_t offset, int orig)
 535 {
 536         return file->f_pos = 0;
 537 }
 538
 539 /*
 540  * The memory devices use the full 32/64 bits of the offset, and so we cannot
 541  * check against negative addresses: they are ok. The return value is weird,
 542  * though, in that case (0).
 543  *
 544  * also note that seeking relative to the "end of file" isn't supported:
 545  * it has no meaning, so it returns -EINVAL.
 546  */
 547 static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
 548 {
 549         loff_t ret;
 550
 551         down(&file->f_dentry->d_inode->i_sem);
 552         switch (orig) {
 553                 case 0:
 554                         file->f_pos = offset;
 555                         ret = file->f_pos;
 556                         force_successful_syscall_return();
 557                         break;
 558                 case 1:
 559                         file->f_pos += offset;
 560                         ret = file->f_pos;
 561                         force_successful_syscall_return();
 562                         break;
 563                 default:
 564                         ret = -EINVAL;
 565         }
 566         up(&file->f_dentry->d_inode->i_sem);
 567         return ret;
 568 }
 569
 570 static int open_port(struct inode * inode, struct file * filp)
 571 {
 572         return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
 573 }
 574
 575 #define mmap_kmem       mmap_mem
 576 #define zero_lseek      null_lseek
 577 #define full_lseek      null_lseek
 578 #define write_zero      write_null
 579 #define read_full       read_zero
 580 #define open_mem        open_port
 581 #define open_kmem       open_mem
 582
 583 static struct file_operations mem_fops = {
 584         .llseek         = memory_lseek,
 585         .read           = read_mem,
 586         .write          = write_mem,
 587         .mmap           = mmap_mem,
 588         .open           = open_mem,
 589 };
 590
 591 static struct file_operations kmem_fops = {
 592         .llseek         = memory_lseek,
 593         .read           = read_kmem,
 594         .write          = write_kmem,
 595         .mmap           = mmap_kmem,
 596         .open           = open_kmem,
 597 };
 598
 599 static struct file_operations null_fops = {
 600         .llseek         = null_lseek,
 601         .read           = read_null,
 602         .write          = write_null,
 603 };
 604
 605 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 606 static struct file_operations port_fops = {
 607         .llseek         = memory_lseek,
 608         .read           = read_port,
 609         .write          = write_port,
 610         .open           = open_port,
 611 };
 612 #endif
 613
 614 static struct file_operations zero_fops = {
 615         .llseek         = zero_lseek,
 616         .read           = read_zero,
 617         .write          = write_zero,
 618         .mmap           = mmap_zero,
 619 };
 620
 621 static struct file_operations full_fops = {
 622         .llseek         = full_lseek,
 623         .read           = read_full,
 624         .write          = write_full,
 625 };
 626
 627 static ssize_t kmsg_write(struct file * file, const char __user * buf,
 628                           size_t count, loff_t *ppos)
 629 {
 630         char *tmp;
 631         int ret;
 632
 633         tmp = kmalloc(count + 1, GFP_KERNEL);
 634         if (tmp == NULL)
 635                 return -ENOMEM;
 636         ret = -EFAULT;
 637         if (!copy_from_user(tmp, buf, count)) {
 638                 tmp[count] = 0;
 639                 ret = printk("%s", tmp);
 640         }
 641         kfree(tmp);
 642         return ret;
 643 }
 644
 645 static struct file_operations kmsg_fops = {
 646         .write =        kmsg_write,
 647 };
 648
 649 static int memory_open(struct inode * inode, struct file * filp)
 650 {
 651         switch (iminor(inode)) {
 652                 case 1:
 653                         filp->f_op = &mem_fops;
 654                         break;
 655                 case 2:
 656                         filp->f_op = &kmem_fops;
 657                         break;
 658                 case 3:
 659                         filp->f_op = &null_fops;
 660                         break;
 661 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 662                 case 4:
 663                         filp->f_op = &port_fops;
 664                         break;
 665 #endif
 666                 case 5:
 667                         filp->f_op = &zero_fops;
 668                         break;
 669                 case 7:
 670                         filp->f_op = &full_fops;
 671                         break;
 672                 case 8:
 673                         filp->f_op = &random_fops;
 674                         break;
 675                 case 9:
 676                         filp->f_op = &urandom_fops;
 677                         break;
 678                 case 11:
 679                         filp->f_op = &kmsg_fops;
 680                         break;
 681                 default:
 682                         return -ENXIO;
 683         }
 684         if (filp->f_op && filp->f_op->open)
 685                 return filp->f_op->open(inode,filp);
 686         return 0;
 687 }
 688
 689 static struct file_operations memory_fops = {
 690         .open           = memory_open,  /* just a selector for the real open */
 691 };
 692
 693 static const struct {
 694         unsigned int            minor;
 695         char                    *name;
 696         umode_t                 mode;
 697         struct file_operations  *fops;
 698 } devlist[] = { /* list of minor devices */
 699         {1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
 700         {2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
 701         {3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
 702 #if defined(CONFIG_ISA) || !defined(__mc68000__)
 703         {4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
 704 #endif
 705         {5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 706         {7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 707         {8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
 708         {9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
 709         {11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
 710 };
 711
 712 static struct class_simple *mem_class;
 713
 714 static int __init chr_dev_init(void)
 715 {
 716         int i;
 717
 718         if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
 719                 printk("unable to get major %d for memory devs\n", MEM_MAJOR);
 720
 721         mem_class = class_simple_create(THIS_MODULE, "mem");
 722         for (i = 0; i < ARRAY_SIZE(devlist); i++) {
 723                 class_simple_device_add(mem_class,
 724                                         MKDEV(MEM_MAJOR, devlist[i].minor),
 725                                         NULL, devlist[i].name);
 726                 devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor),
 727                                 S_IFCHR | devlist[i].mode, devlist[i].name);
 728         }
 729
 730         return 0;
 731 }
 732
 733 fs_initcall(chr_dev_init);