arch/s390/kernel/setup.c

   1 /*
   2  *  arch/s390/kernel/setup.c
   3  *
   4  *  S390 version
   5  *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
   6  *    Author(s): Hartmut Penner (hp@de.ibm.com),
   7  *               Martin Schwidefsky (schwidefsky@de.ibm.com)
   8  *
   9  *  Derived from "arch/i386/kernel/setup.c"
  10  *    Copyright (C) 1995, Linus Torvalds
  11  */
  12
  13 /*
  14  * This file handles the architecture-dependent parts of initialization
  15  */
  16
  17 #include <linux/errno.h>
  18 #include <linux/module.h>
  19 #include <linux/sched.h>
  20 #include <linux/kernel.h>
  21 #include <linux/mm.h>
  22 #include <linux/stddef.h>
  23 #include <linux/unistd.h>
  24 #include <linux/ptrace.h>
  25 #include <linux/slab.h>
  26 #include <linux/user.h>
  27 #include <linux/a.out.h>
  28 #include <linux/tty.h>
  29 #include <linux/ioport.h>
  30 #include <linux/delay.h>
  31 #include <linux/config.h>
  32 #include <linux/init.h>
  33 #include <linux/initrd.h>
  34 #include <linux/bootmem.h>
  35 #include <linux/root_dev.h>
  36 #include <linux/console.h>
  37 #include <linux/seq_file.h>
  38 #include <linux/kernel_stat.h>
  39
  40 #include <asm/uaccess.h>
  41 #include <asm/system.h>
  42 #include <asm/smp.h>
  43 #include <asm/mmu_context.h>
  44 #include <asm/cpcmd.h>
  45 #include <asm/lowcore.h>
  46 #include <asm/irq.h>
  47
  48 /*
  49  * Machine setup..
  50  */
  51 unsigned int console_mode = 0;
  52 unsigned int console_devno = -1;
  53 unsigned int console_irq = -1;
  54 unsigned long memory_size = 0;
  55 unsigned long machine_flags = 0;
  56 unsigned int default_storage_key = 0;
  57 struct {
  58         unsigned long addr, size, type;
  59 } memory_chunk[MEMORY_CHUNKS] = { { 0 } };
  60 #define CHUNK_READ_WRITE 0
  61 #define CHUNK_READ_ONLY 1
  62 volatile int __cpu_logical_map[NR_CPUS]; /* logical cpu to cpu address */
  63
  64 /*
  65  * Setup options
  66  */
  67 extern int _text,_etext, _edata, _end;
  68
  69 /*
  70  * This is set up by the setup-routine at boot-time
  71  * for S390 need to find out, what we have to setup
  72  * using address 0x10400 ...
  73  */
  74
  75 #include <asm/setup.h>
  76
  77 static char command_line[COMMAND_LINE_SIZE] = { 0, };
  78
  79 static struct resource code_resource = {
  80         .name  = "Kernel code",
  81         .flags = IORESOURCE_BUSY | IORESOURCE_MEM,
  82 };
  83
  84 static struct resource data_resource = {
  85         .name = "Kernel data",
  86         .flags = IORESOURCE_BUSY | IORESOURCE_MEM,
  87 };
  88
  89 /*
  90  * cpu_init() initializes state that is per-CPU.
  91  */
  92 void __devinit cpu_init (void)
  93 {
  94         int addr = hard_smp_processor_id();
  95
  96         /*
  97          * Store processor id in lowcore (used e.g. in timer_interrupt)
  98          */
  99         asm volatile ("stidp %0": "=m" (S390_lowcore.cpu_data.cpu_id));
 100         S390_lowcore.cpu_data.cpu_addr = addr;
 101
 102         /*
 103          * Force FPU initialization:
 104          */
 105         clear_thread_flag(TIF_USEDFPU);
 106         clear_used_math();
 107
 108         atomic_inc(&init_mm.mm_count);
 109         current->active_mm = &init_mm;
 110         if (current->mm)
 111                 BUG();
 112         enter_lazy_tlb(&init_mm, current);
 113 }
 114
 115 /*
 116  * VM halt and poweroff setup routines
 117  */
 118 char vmhalt_cmd[128] = "";
 119 char vmpoff_cmd[128] = "";
 120
 121 static inline void strncpy_skip_quote(char *dst, char *src, int n)
 122 {
 123         int sx, dx;
 124
 125         dx = 0;
 126         for (sx = 0; src[sx] != 0; sx++) {
 127                 if (src[sx] == '"') continue;
 128                 dst[dx++] = src[sx];
 129                 if (dx >= n) break;
 130         }
 131 }
 132
 133 static int __init vmhalt_setup(char *str)
 134 {
 135         strncpy_skip_quote(vmhalt_cmd, str, 127);
 136         vmhalt_cmd[127] = 0;
 137         return 1;
 138 }
 139
 140 __setup("vmhalt=", vmhalt_setup);
 141
 142 static int __init vmpoff_setup(char *str)
 143 {
 144         strncpy_skip_quote(vmpoff_cmd, str, 127);
 145         vmpoff_cmd[127] = 0;
 146         return 1;
 147 }
 148
 149 __setup("vmpoff=", vmpoff_setup);
 150
 151 /*
 152  * condev= and conmode= setup parameter.
 153  */
 154
 155 static int __init condev_setup(char *str)
 156 {
 157         int vdev;
 158
 159         vdev = simple_strtoul(str, &str, 0);
 160         if (vdev >= 0 && vdev < 65536) {
 161                 console_devno = vdev;
 162                 console_irq = -1;
 163         }
 164         return 1;
 165 }
 166
 167 __setup("condev=", condev_setup);
 168
 169 static int __init conmode_setup(char *str)
 170 {
 171 #if defined(CONFIG_SCLP_CONSOLE)
 172         if (strncmp(str, "hwc", 4) == 0 || strncmp(str, "sclp", 5) == 0)
 173                 SET_CONSOLE_SCLP;
 174 #endif
 175 #if defined(CONFIG_TN3215_CONSOLE)
 176         if (strncmp(str, "3215", 5) == 0)
 177                 SET_CONSOLE_3215;
 178 #endif
 179 #if defined(CONFIG_TN3270_CONSOLE)
 180         if (strncmp(str, "3270", 5) == 0)
 181                 SET_CONSOLE_3270;
 182 #endif
 183         return 1;
 184 }
 185
 186 __setup("conmode=", conmode_setup);
 187
 188 static void __init conmode_default(void)
 189 {
 190         char query_buffer[1024];
 191         char *ptr;
 192
 193         if (MACHINE_IS_VM) {
 194                 __cpcmd("QUERY CONSOLE", query_buffer, 1024);
 195                 console_devno = simple_strtoul(query_buffer + 5, NULL, 16);
 196                 ptr = strstr(query_buffer, "SUBCHANNEL =");
 197                 console_irq = simple_strtoul(ptr + 13, NULL, 16);
 198                 __cpcmd("QUERY TERM", query_buffer, 1024);
 199                 ptr = strstr(query_buffer, "CONMODE");
 200                 /*
 201                  * Set the conmode to 3215 so that the device recognition
 202                  * will set the cu_type of the console to 3215. If the
 203                  * conmode is 3270 and we don't set it back then both
 204                  * 3215 and the 3270 driver will try to access the console
 205                  * device (3215 as console and 3270 as normal tty).
 206                  */
 207                 __cpcmd("TERM CONMODE 3215", NULL, 0);
 208                 if (ptr == NULL) {
 209 #if defined(CONFIG_SCLP_CONSOLE)
 210                         SET_CONSOLE_SCLP;
 211 #endif
 212                         return;
 213                 }
 214                 if (strncmp(ptr + 8, "3270", 4) == 0) {
 215 #if defined(CONFIG_TN3270_CONSOLE)
 216                         SET_CONSOLE_3270;
 217 #elif defined(CONFIG_TN3215_CONSOLE)
 218                         SET_CONSOLE_3215;
 219 #elif defined(CONFIG_SCLP_CONSOLE)
 220                         SET_CONSOLE_SCLP;
 221 #endif
 222                 } else if (strncmp(ptr + 8, "3215", 4) == 0) {
 223 #if defined(CONFIG_TN3215_CONSOLE)
 224                         SET_CONSOLE_3215;
 225 #elif defined(CONFIG_TN3270_CONSOLE)
 226                         SET_CONSOLE_3270;
 227 #elif defined(CONFIG_SCLP_CONSOLE)
 228                         SET_CONSOLE_SCLP;
 229 #endif
 230                 }
 231         } else if (MACHINE_IS_P390) {
 232 #if defined(CONFIG_TN3215_CONSOLE)
 233                 SET_CONSOLE_3215;
 234 #elif defined(CONFIG_TN3270_CONSOLE)
 235                 SET_CONSOLE_3270;
 236 #endif
 237         } else {
 238 #if defined(CONFIG_SCLP_CONSOLE)
 239                 SET_CONSOLE_SCLP;
 240 #endif
 241         }
 242 }
 243
 244 #ifdef CONFIG_SMP
 245 extern void machine_restart_smp(char *);
 246 extern void machine_halt_smp(void);
 247 extern void machine_power_off_smp(void);
 248
 249 void (*_machine_restart)(char *command) = machine_restart_smp;
 250 void (*_machine_halt)(void) = machine_halt_smp;
 251 void (*_machine_power_off)(void) = machine_power_off_smp;
 252 #else
 253 /*
 254  * Reboot, halt and power_off routines for non SMP.
 255  */
 256 extern void reipl(unsigned long devno);
 257 static void do_machine_restart_nonsmp(char * __unused)
 258 {
 259         if (MACHINE_IS_VM)
 260                 cpcmd ("IPL", NULL, 0);
 261         else
 262                 reipl (0x10000 | S390_lowcore.ipl_device);
 263 }
 264
 265 static void do_machine_halt_nonsmp(void)
 266 {
 267         if (MACHINE_IS_VM && strlen(vmhalt_cmd) > 0)
 268                 cpcmd(vmhalt_cmd, NULL, 0);
 269         signal_processor(smp_processor_id(), sigp_stop_and_store_status);
 270 }
 271
 272 static void do_machine_power_off_nonsmp(void)
 273 {
 274         if (MACHINE_IS_VM && strlen(vmpoff_cmd) > 0)
 275                 cpcmd(vmpoff_cmd, NULL, 0);
 276         signal_processor(smp_processor_id(), sigp_stop_and_store_status);
 277 }
 278
 279 void (*_machine_restart)(char *command) = do_machine_restart_nonsmp;
 280 void (*_machine_halt)(void) = do_machine_halt_nonsmp;
 281 void (*_machine_power_off)(void) = do_machine_power_off_nonsmp;
 282 #endif
 283
 284  /*
 285  * Reboot, halt and power_off stubs. They just call _machine_restart,
 286  * _machine_halt or _machine_power_off.
 287  */
 288
 289 void machine_restart(char *command)
 290 {
 291         console_unblank();
 292         _machine_restart(command);
 293 }
 294
 295 EXPORT_SYMBOL(machine_restart);
 296
 297 void machine_halt(void)
 298 {
 299         console_unblank();
 300         _machine_halt();
 301 }
 302
 303 EXPORT_SYMBOL(machine_halt);
 304
 305 void machine_power_off(void)
 306 {
 307         console_unblank();
 308         _machine_power_off();
 309 }
 310
 311 EXPORT_SYMBOL(machine_power_off);
 312
 313 /*
 314  * Setup function called from init/main.c just after the banner
 315  * was printed.
 316  */
 317 extern char _pstart, _pend, _stext;
 318
 319 void __init setup_arch(char **cmdline_p)
 320 {
 321         unsigned long bootmap_size;
 322         unsigned long memory_start, memory_end;
 323         char c = ' ', cn, *to = command_line, *from = COMMAND_LINE;
 324         unsigned long start_pfn, end_pfn;
 325         static unsigned int smptrap=0;
 326         unsigned long delay = 0;
 327         struct _lowcore *lc;
 328         int i;
 329
 330         if (smptrap)
 331                 return;
 332         smptrap=1;
 333
 334         /*
 335          * print what head.S has found out about the machine
 336          */
 337 #ifndef CONFIG_ARCH_S390X
 338         printk((MACHINE_IS_VM) ?
 339                "We are running under VM (31 bit mode)\n" :
 340                "We are running native (31 bit mode)\n");
 341         printk((MACHINE_HAS_IEEE) ?
 342                "This machine has an IEEE fpu\n" :
 343                "This machine has no IEEE fpu\n");
 344 #else /* CONFIG_ARCH_S390X */
 345         printk((MACHINE_IS_VM) ?
 346                "We are running under VM (64 bit mode)\n" :
 347                "We are running native (64 bit mode)\n");
 348 #endif /* CONFIG_ARCH_S390X */
 349
 350         ROOT_DEV = Root_RAM0;
 351         memory_start = (unsigned long) &_end;    /* fixit if use $CODELO etc*/
 352 #ifndef CONFIG_ARCH_S390X
 353         memory_end = memory_size & ~0x400000UL;  /* align memory end to 4MB */
 354         /*
 355          * We need some free virtual space to be able to do vmalloc.
 356          * On a machine with 2GB memory we make sure that we have at
 357          * least 128 MB free space for vmalloc.
 358          */
 359         if (memory_end > 1920*1024*1024)
 360                 memory_end = 1920*1024*1024;
 361 #else /* CONFIG_ARCH_S390X */
 362         memory_end = memory_size & ~0x200000UL;  /* detected in head.s */
 363 #endif /* CONFIG_ARCH_S390X */
 364         init_mm.start_code = PAGE_OFFSET;
 365         init_mm.end_code = (unsigned long) &_etext;
 366         init_mm.end_data = (unsigned long) &_edata;
 367         init_mm.brk = (unsigned long) &_end;
 368
 369         code_resource.start = (unsigned long) &_text;
 370         code_resource.end = (unsigned long) &_etext - 1;
 371         data_resource.start = (unsigned long) &_etext;
 372         data_resource.end = (unsigned long) &_edata - 1;
 373
 374         /* Save unparsed command line copy for /proc/cmdline */
 375         memcpy(saved_command_line, COMMAND_LINE, COMMAND_LINE_SIZE);
 376         saved_command_line[COMMAND_LINE_SIZE-1] = '\0';
 377
 378         for (;;) {
 379                 /*
 380                  * "mem=XXX[kKmM]" sets memsize
 381                  */
 382                 if (c == ' ' && strncmp(from, "mem=", 4) == 0) {
 383                         memory_end = simple_strtoul(from+4, &from, 0);
 384                         if ( *from == 'K' || *from == 'k' ) {
 385                                 memory_end = memory_end << 10;
 386                                 from++;
 387                         } else if ( *from == 'M' || *from == 'm' ) {
 388                                 memory_end = memory_end << 20;
 389                                 from++;
 390                         }
 391                 }
 392                 /*
 393                  * "ipldelay=XXX[sm]" sets ipl delay in seconds or minutes
 394                  */
 395                 if (c == ' ' && strncmp(from, "ipldelay=", 9) == 0) {
 396                         delay = simple_strtoul(from+9, &from, 0);
 397                         if (*from == 's' || *from == 'S') {
 398                                 delay = delay*1000000;
 399                                 from++;
 400                         } else if (*from == 'm' || *from == 'M') {
 401                                 delay = delay*60*1000000;
 402                                 from++;
 403                         }
 404                         /* now wait for the requested amount of time */
 405                         udelay(delay);
 406                 }
 407                 cn = *(from++);
 408                 if (!cn)
 409                         break;
 410                 if (cn == '\n')
 411                         cn = ' ';  /* replace newlines with space */
 412                 if (cn == 0x0d)
 413                         cn = ' ';  /* replace 0x0d with space */
 414                 if (cn == ' ' && c == ' ')
 415                         continue;  /* remove additional spaces */
 416                 c = cn;
 417                 if (to - command_line >= COMMAND_LINE_SIZE)
 418                         break;
 419                 *(to++) = c;
 420         }
 421         if (c == ' ' && to > command_line) to--;
 422         *to = '\0';
 423         *cmdline_p = command_line;
 424
 425         /*
 426          * partially used pages are not usable - thus
 427          * we are rounding upwards:
 428          */
 429         start_pfn = (__pa(&_end) + PAGE_SIZE - 1) >> PAGE_SHIFT;
 430         end_pfn = max_pfn = memory_end >> PAGE_SHIFT;
 431
 432         /*
 433          * Initialize the boot-time allocator (with low memory only):
 434          */
 435         bootmap_size = init_bootmem(start_pfn, end_pfn);
 436
 437         /*
 438          * Register RAM areas with the bootmem allocator.
 439          */
 440         for (i = 0; i < 16 && memory_chunk[i].size > 0; i++) {
 441                 unsigned long start_chunk, end_chunk;
 442
 443                 if (memory_chunk[i].type != CHUNK_READ_WRITE)
 444                         continue;
 445                 start_chunk = (memory_chunk[i].addr + PAGE_SIZE - 1);
 446                 start_chunk >>= PAGE_SHIFT;
 447                 end_chunk = (memory_chunk[i].addr + memory_chunk[i].size);
 448                 end_chunk >>= PAGE_SHIFT;
 449                 if (start_chunk < start_pfn)
 450                         start_chunk = start_pfn;
 451                 if (end_chunk > end_pfn)
 452                         end_chunk = end_pfn;
 453                 if (start_chunk < end_chunk)
 454                         free_bootmem(start_chunk << PAGE_SHIFT,
 455                                      (end_chunk - start_chunk) << PAGE_SHIFT);
 456         }
 457
 458         /*
 459          * Reserve the bootmem bitmap itself as well. We do this in two
 460          * steps (first step was init_bootmem()) because this catches
 461          * the (very unlikely) case of us accidentally initializing the
 462          * bootmem allocator with an invalid RAM area.
 463          */
 464         reserve_bootmem(start_pfn << PAGE_SHIFT, bootmap_size);
 465
 466 #ifdef CONFIG_BLK_DEV_INITRD
 467         if (INITRD_START) {
 468                 if (INITRD_START + INITRD_SIZE <= memory_end) {
 469                         reserve_bootmem(INITRD_START, INITRD_SIZE);
 470                         initrd_start = INITRD_START;
 471                         initrd_end = initrd_start + INITRD_SIZE;
 472                 } else {
 473                         printk("initrd extends beyond end of memory "
 474                                "(0x%08lx > 0x%08lx)\ndisabling initrd\n",
 475                                initrd_start + INITRD_SIZE, memory_end);
 476                         initrd_start = initrd_end = 0;
 477                 }
 478         }
 479 #endif
 480
 481         for (i = 0; i < 16 && memory_chunk[i].size > 0; i++) {
 482                 struct resource *res;
 483
 484                 res = alloc_bootmem_low(sizeof(struct resource));
 485                 res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
 486
 487                 switch (memory_chunk[i].type) {
 488                 case CHUNK_READ_WRITE:
 489                         res->name = "System RAM";
 490                         break;
 491                 case CHUNK_READ_ONLY:
 492                         res->name = "System ROM";
 493                         res->flags |= IORESOURCE_READONLY;
 494                         break;
 495                 default:
 496                         res->name = "reserved";
 497                 }
 498                 res->start = memory_chunk[i].addr;
 499                 res->end = memory_chunk[i].addr +  memory_chunk[i].size - 1;
 500                 request_resource(&iomem_resource, res);
 501                 request_resource(res, &code_resource);
 502                 request_resource(res, &data_resource);
 503         }
 504
 505         /*
 506          * Setup lowcore for boot cpu
 507          */
 508 #ifndef CONFIG_ARCH_S390X
 509         lc = (struct _lowcore *) __alloc_bootmem(PAGE_SIZE, PAGE_SIZE, 0);
 510         memset(lc, 0, PAGE_SIZE);
 511 #else /* CONFIG_ARCH_S390X */
 512         lc = (struct _lowcore *) __alloc_bootmem(2*PAGE_SIZE, 2*PAGE_SIZE, 0);
 513         memset(lc, 0, 2*PAGE_SIZE);
 514 #endif /* CONFIG_ARCH_S390X */
 515         lc->restart_psw.mask = PSW_BASE_BITS;
 516         lc->restart_psw.addr =
 517                 PSW_ADDR_AMODE | (unsigned long) restart_int_handler;
 518         lc->external_new_psw.mask = PSW_KERNEL_BITS;
 519         lc->external_new_psw.addr =
 520                 PSW_ADDR_AMODE | (unsigned long) ext_int_handler;
 521         lc->svc_new_psw.mask = PSW_KERNEL_BITS | PSW_MASK_IO | PSW_MASK_EXT;
 522         lc->svc_new_psw.addr = PSW_ADDR_AMODE | (unsigned long) system_call;
 523         lc->program_new_psw.mask = PSW_KERNEL_BITS;
 524         lc->program_new_psw.addr =
 525                 PSW_ADDR_AMODE | (unsigned long)pgm_check_handler;
 526         lc->mcck_new_psw.mask = PSW_KERNEL_BITS;
 527         lc->mcck_new_psw.addr =
 528                 PSW_ADDR_AMODE | (unsigned long) mcck_int_handler;
 529         lc->io_new_psw.mask = PSW_KERNEL_BITS;
 530         lc->io_new_psw.addr = PSW_ADDR_AMODE | (unsigned long) io_int_handler;
 531         lc->ipl_device = S390_lowcore.ipl_device;
 532         lc->jiffy_timer = -1LL;
 533         lc->kernel_stack = ((unsigned long) &init_thread_union) + THREAD_SIZE;
 534         lc->async_stack = (unsigned long)
 535                 __alloc_bootmem(ASYNC_SIZE, ASYNC_SIZE, 0) + ASYNC_SIZE;
 536 #ifdef CONFIG_CHECK_STACK
 537         lc->panic_stack = (unsigned long)
 538                 __alloc_bootmem(PAGE_SIZE, PAGE_SIZE, 0) + PAGE_SIZE;
 539 #endif
 540         lc->current_task = (unsigned long) init_thread_union.thread_info.task;
 541         lc->thread_info = (unsigned long) &init_thread_union;
 542 #ifdef CONFIG_ARCH_S390X
 543         if (MACHINE_HAS_DIAG44)
 544                 lc->diag44_opcode = 0x83000044;
 545         else
 546                 lc->diag44_opcode = 0x07000700;
 547 #endif /* CONFIG_ARCH_S390X */
 548         set_prefix((u32)(unsigned long) lc);
 549         cpu_init();
 550         __cpu_logical_map[0] = S390_lowcore.cpu_data.cpu_addr;
 551
 552         /*
 553          * Create kernel page tables and switch to virtual addressing.
 554          */
 555         paging_init();
 556
 557         /* Setup default console */
 558         conmode_default();
 559 }
 560
 561 void print_cpu_info(struct cpuinfo_S390 *cpuinfo)
 562 {
 563    printk("cpu %d "
 564 #ifdef CONFIG_SMP
 565            "phys_idx=%d "
 566 #endif
 567            "vers=%02X ident=%06X machine=%04X unused=%04X\n",
 568            cpuinfo->cpu_nr,
 569 #ifdef CONFIG_SMP
 570            cpuinfo->cpu_addr,
 571 #endif
 572            cpuinfo->cpu_id.version,
 573            cpuinfo->cpu_id.ident,
 574            cpuinfo->cpu_id.machine,
 575            cpuinfo->cpu_id.unused);
 576 }
 577
 578 /*
 579  * show_cpuinfo - Get information on one CPU for use by procfs.
 580  */
 581
 582 static int show_cpuinfo(struct seq_file *m, void *v)
 583 {
 584         struct cpuinfo_S390 *cpuinfo;
 585         unsigned long n = (unsigned long) v - 1;
 586
 587         if (!n) {
 588                 seq_printf(m, "vendor_id       : IBM/S390\n"
 589                                "# processors    : %i\n"
 590                                "bogomips per cpu: %lu.%02lu\n",
 591                                num_online_cpus(), loops_per_jiffy/(500000/HZ),
 592                                (loops_per_jiffy/(5000/HZ))%100);
 593         }
 594         if (cpu_online(n)) {
 595 #ifdef CONFIG_SMP
 596                 if (smp_processor_id() == n)
 597                         cpuinfo = &S390_lowcore.cpu_data;
 598                 else
 599                         cpuinfo = &lowcore_ptr[n]->cpu_data;
 600 #else
 601                 cpuinfo = &S390_lowcore.cpu_data;
 602 #endif
 603                 seq_printf(m, "processor %li: "
 604                                "version = %02X,  "
 605                                "identification = %06X,  "
 606                                "machine = %04X\n",
 607                                n, cpuinfo->cpu_id.version,
 608                                cpuinfo->cpu_id.ident,
 609                                cpuinfo->cpu_id.machine);
 610         }
 611         return 0;
 612 }
 613
 614 static void *c_start(struct seq_file *m, loff_t *pos)
 615 {
 616         return *pos < NR_CPUS ? (void *)((unsigned long) *pos + 1) : NULL;
 617 }
 618 static void *c_next(struct seq_file *m, void *v, loff_t *pos)
 619 {
 620         ++*pos;
 621         return c_start(m, pos);
 622 }
 623 static void c_stop(struct seq_file *m, void *v)
 624 {
 625 }
 626 struct seq_operations cpuinfo_op = {
 627         .start  = c_start,
 628         .next   = c_next,
 629         .stop   = c_stop,
 630         .show   = show_cpuinfo,
 631 };
 632