linux/Documentation/filesystems/spufs.txt
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   1SPUFS(2)                   Linux Programmer's Manual                  SPUFS(2)
   2
   3
   4
   5NAME
   6       spufs - the SPU file system
   7
   8
   9DESCRIPTION
  10       The SPU file system is used on PowerPC machines that implement the Cell
  11       Broadband Engine Architecture in order to access Synergistic  Processor
  12       Units (SPUs).
  13
  14       The file system provides a name space similar to posix shared memory or
  15       message queues. Users that have write permissions on  the  file  system
  16       can use spu_create(2) to establish SPU contexts in the spufs root.
  17
  18       Every SPU context is represented by a directory containing a predefined
  19       set of files. These files can be used for manipulating the state of the
  20       logical SPU. Users can change permissions on those files, but not actu-
  21       ally add or remove files.
  22
  23
  24MOUNT OPTIONS
  25       uid=<uid>
  26              set the user owning the mount point, the default is 0 (root).
  27
  28       gid=<gid>
  29              set the group owning the mount point, the default is 0 (root).
  30
  31
  32FILES
  33       The files in spufs mostly follow the standard behavior for regular sys-
  34       tem  calls like read(2) or write(2), but often support only a subset of
  35       the operations supported on regular file systems. This list details the
  36       supported  operations  and  the  deviations  from  the behaviour in the
  37       respective man pages.
  38
  39       All files that support the read(2) operation also support readv(2)  and
  40       all  files  that support the write(2) operation also support writev(2).
  41       All files support the access(2) and stat(2) family of  operations,  but
  42       only  the  st_mode,  st_nlink,  st_uid and st_gid fields of struct stat
  43       contain reliable information.
  44
  45       All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2)  opera-
  46       tions,  but  will  not be able to grant permissions that contradict the
  47       possible operations, e.g. read access on the wbox file.
  48
  49       The current set of files is:
  50
  51
  52   /mem
  53       the contents of the local storage memory  of  the  SPU.   This  can  be
  54       accessed  like  a regular shared memory file and contains both code and
  55       data in the address space of the SPU.  The possible  operations  on  an
  56       open mem file are:
  57
  58       read(2), pread(2), write(2), pwrite(2), lseek(2)
  59              These  operate  as  documented, with the exception that seek(2),
  60              write(2) and pwrite(2) are not supported beyond the end  of  the
  61              file. The file size is the size of the local storage of the SPU,
  62              which normally is 256 kilobytes.
  63
  64       mmap(2)
  65              Mapping mem into the process address space gives access  to  the
  66              SPU  local  storage  within  the  process  address  space.  Only
  67              MAP_SHARED mappings are allowed.
  68
  69
  70   /mbox
  71       The first SPU to CPU communication mailbox. This file is read-only  and
  72       can  be  read  in  units of 32 bits.  The file can only be used in non-
  73       blocking mode and it even poll() will not block on  it.   The  possible
  74       operations on an open mbox file are:
  75
  76       read(2)
  77              If  a  count smaller than four is requested, read returns -1 and
  78              sets errno to EINVAL.  If there is no data available in the mail
  79              box,  the  return  value  is set to -1 and errno becomes EAGAIN.
  80              When data has been read successfully, four bytes are  placed  in
  81              the data buffer and the value four is returned.
  82
  83
  84   /ibox
  85       The  second  SPU  to CPU communication mailbox. This file is similar to
  86       the first mailbox file, but can be read in blocking I/O mode,  and  the
  87       poll  family of system calls can be used to wait for it.  The  possible
  88       operations on an open ibox file are:
  89
  90       read(2)
  91              If a count smaller than four is requested, read returns  -1  and
  92              sets errno to EINVAL.  If there is no data available in the mail
  93              box and the file descriptor has been opened with O_NONBLOCK, the
  94              return value is set to -1 and errno becomes EAGAIN.
  95
  96              If  there  is  no  data  available  in the mail box and the file
  97              descriptor has been opened without  O_NONBLOCK,  the  call  will
  98              block  until  the  SPU  writes to its interrupt mailbox channel.
  99              When data has been read successfully, four bytes are  placed  in
 100              the data buffer and the value four is returned.
 101
 102       poll(2)
 103              Poll  on  the  ibox  file returns (POLLIN | POLLRDNORM) whenever
 104              data is available for reading.
 105
 106
 107   /wbox
 108       The CPU to SPU communation mailbox. It is write-only and can be written
 109       in  units  of  32  bits. If the mailbox is full, write() will block and
 110       poll can be used to wait for it becoming  empty  again.   The  possible
 111       operations  on  an open wbox file are: write(2) If a count smaller than
 112       four is requested, write returns -1 and sets errno to EINVAL.  If there
 113       is  no space available in the mail box and the file descriptor has been
 114       opened with O_NONBLOCK, the return value is set to -1 and errno becomes
 115       EAGAIN.
 116
 117       If  there is no space available in the mail box and the file descriptor
 118       has been opened without O_NONBLOCK, the call will block until  the  SPU
 119       reads  from  its PPE mailbox channel.  When data has been read success-
 120       fully, four bytes are placed in the data buffer and the value  four  is
 121       returned.
 122
 123       poll(2)
 124              Poll  on  the  ibox file returns (POLLOUT | POLLWRNORM) whenever
 125              space is available for writing.
 126
 127
 128   /mbox_stat
 129   /ibox_stat
 130   /wbox_stat
 131       Read-only files that contain the length of the current queue, i.e.  how
 132       many  words  can  be  read  from  mbox or ibox or how many words can be
 133       written to wbox without blocking.  The files can be read only in 4-byte
 134       units  and  return  a  big-endian  binary integer number.  The possible
 135       operations on an open *box_stat file are:
 136
 137       read(2)
 138              If a count smaller than four is requested, read returns  -1  and
 139              sets errno to EINVAL.  Otherwise, a four byte value is placed in
 140              the data buffer, containing the number of elements that  can  be
 141              read  from  (for  mbox_stat  and  ibox_stat)  or written to (for
 142              wbox_stat) the respective mail box without blocking or resulting
 143              in EAGAIN.
 144
 145
 146   /npc
 147   /decr
 148   /decr_status
 149   /spu_tag_mask
 150   /event_mask
 151   /srr0
 152       Internal  registers  of  the SPU. The representation is an ASCII string
 153       with the numeric value of the next instruction to  be  executed.  These
 154       can  be  used in read/write mode for debugging, but normal operation of
 155       programs should not rely on them because access to any of  them  except
 156       npc requires an SPU context save and is therefore very inefficient.
 157
 158       The contents of these files are:
 159
 160       npc                 Next Program Counter
 161
 162       decr                SPU Decrementer
 163
 164       decr_status         Decrementer Status
 165
 166       spu_tag_mask        MFC tag mask for SPU DMA
 167
 168       event_mask          Event mask for SPU interrupts
 169
 170       srr0                Interrupt Return address register
 171
 172
 173       The   possible   operations   on   an   open  npc,  decr,  decr_status,
 174       spu_tag_mask, event_mask or srr0 file are:
 175
 176       read(2)
 177              When the count supplied to the read call  is  shorter  than  the
 178              required  length for the pointer value plus a newline character,
 179              subsequent reads from the same file descriptor  will  result  in
 180              completing  the string, regardless of changes to the register by
 181              a running SPU task.  When a complete string has been  read,  all
 182              subsequent read operations will return zero bytes and a new file
 183              descriptor needs to be opened to read the value again.
 184
 185       write(2)
 186              A write operation on the file results in setting the register to
 187              the  value  given  in  the string. The string is parsed from the
 188              beginning to the first non-numeric character or the end  of  the
 189              buffer.  Subsequent writes to the same file descriptor overwrite
 190              the previous setting.
 191
 192
 193   /fpcr
 194       This file gives access to the Floating Point Status and Control  Regis-
 195       ter as a four byte long file. The operations on the fpcr file are:
 196
 197       read(2)
 198              If  a  count smaller than four is requested, read returns -1 and
 199              sets errno to EINVAL.  Otherwise, a four byte value is placed in
 200              the data buffer, containing the current value of the fpcr regis-
 201              ter.
 202
 203       write(2)
 204              If a count smaller than four is requested, write returns -1  and
 205              sets  errno  to  EINVAL.  Otherwise, a four byte value is copied
 206              from the data buffer, updating the value of the fpcr register.
 207
 208
 209   /signal1
 210   /signal2
 211       The two signal notification channels of an SPU.  These  are  read-write
 212       files  that  operate  on  a 32 bit word.  Writing to one of these files
 213       triggers an interrupt on the SPU.  The  value  written  to  the  signal
 214       files can be read from the SPU through a channel read or from host user
 215       space through the file.  After the value has been read by the  SPU,  it
 216       is  reset  to zero.  The possible operations on an open signal1 or sig-
 217       nal2 file are:
 218
 219       read(2)
 220              If a count smaller than four is requested, read returns  -1  and
 221              sets errno to EINVAL.  Otherwise, a four byte value is placed in
 222              the data buffer, containing the current value of  the  specified
 223              signal notification register.
 224
 225       write(2)
 226              If  a count smaller than four is requested, write returns -1 and
 227              sets errno to EINVAL.  Otherwise, a four byte  value  is  copied
 228              from the data buffer, updating the value of the specified signal
 229              notification register.  The signal  notification  register  will
 230              either be replaced with the input data or will be updated to the
 231              bitwise OR or the old value and the input data, depending on the
 232              contents  of  the  signal1_type,  or  signal2_type respectively,
 233              file.
 234
 235
 236   /signal1_type
 237   /signal2_type
 238       These two files change the behavior of the signal1 and signal2  notifi-
 239       cation  files.  The  contain  a numerical ASCII string which is read as
 240       either "1" or "0".  In mode 0 (overwrite), the  hardware  replaces  the
 241       contents of the signal channel with the data that is written to it.  in
 242       mode 1 (logical OR), the hardware accumulates the bits that are  subse-
 243       quently written to it.  The possible operations on an open signal1_type
 244       or signal2_type file are:
 245
 246       read(2)
 247              When the count supplied to the read call  is  shorter  than  the
 248              required  length  for the digit plus a newline character, subse-
 249              quent reads from the same file descriptor will  result  in  com-
 250              pleting  the  string.  When a complete string has been read, all
 251              subsequent read operations will return zero bytes and a new file
 252              descriptor needs to be opened to read the value again.
 253
 254       write(2)
 255              A write operation on the file results in setting the register to
 256              the value given in the string. The string  is  parsed  from  the
 257              beginning  to  the first non-numeric character or the end of the
 258              buffer.  Subsequent writes to the same file descriptor overwrite
 259              the previous setting.
 260
 261
 262EXAMPLES
 263       /etc/fstab entry
 264              none      /spu      spufs     gid=spu   0    0
 265
 266
 267AUTHORS
 268       Arnd  Bergmann  <arndb@de.ibm.com>,  Mark  Nutter <mnutter@us.ibm.com>,
 269       Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
 270
 271SEE ALSO
 272       capabilities(7), close(2), spu_create(2), spu_run(2), spufs(7)
 273
 274
 275
 276Linux                             2005-09-28                          SPUFS(2)
 277
 278------------------------------------------------------------------------------
 279
 280SPU_RUN(2)                 Linux Programmer's Manual                SPU_RUN(2)
 281
 282
 283
 284NAME
 285       spu_run - execute an spu context
 286
 287
 288SYNOPSIS
 289       #include <sys/spu.h>
 290
 291       int spu_run(int fd, unsigned int *npc, unsigned int *event);
 292
 293DESCRIPTION
 294       The  spu_run system call is used on PowerPC machines that implement the
 295       Cell Broadband Engine Architecture in order to access Synergistic  Pro-
 296       cessor  Units  (SPUs).  It  uses the fd that was returned from spu_cre-
 297       ate(2) to address a specific SPU context. When the context gets  sched-
 298       uled  to a physical SPU, it starts execution at the instruction pointer
 299       passed in npc.
 300
 301       Execution of SPU code happens synchronously, meaning that spu_run  does
 302       not  return  while the SPU is still running. If there is a need to exe-
 303       cute SPU code in parallel with other code on either  the  main  CPU  or
 304       other  SPUs,  you  need to create a new thread of execution first, e.g.
 305       using the pthread_create(3) call.
 306
 307       When spu_run returns, the current value of the SPU instruction  pointer
 308       is  written back to npc, so you can call spu_run again without updating
 309       the pointers.
 310
 311       event can be a NULL pointer or point to an extended  status  code  that
 312       gets  filled  when spu_run returns. It can be one of the following con-
 313       stants:
 314
 315       SPE_EVENT_DMA_ALIGNMENT
 316              A DMA alignment error
 317
 318       SPE_EVENT_SPE_DATA_SEGMENT
 319              A DMA segmentation error
 320
 321       SPE_EVENT_SPE_DATA_STORAGE
 322              A DMA storage error
 323
 324       If NULL is passed as the event argument, these errors will result in  a
 325       signal delivered to the calling process.
 326
 327RETURN VALUE
 328       spu_run  returns the value of the spu_status register or -1 to indicate
 329       an error and set errno to one of the error  codes  listed  below.   The
 330       spu_status  register  value  contains  a  bit  mask of status codes and
 331       optionally a 14 bit code returned from the stop-and-signal  instruction
 332       on the SPU. The bit masks for the status codes are:
 333
 334       0x02   SPU was stopped by stop-and-signal.
 335
 336       0x04   SPU was stopped by halt.
 337
 338       0x08   SPU is waiting for a channel.
 339
 340       0x10   SPU is in single-step mode.
 341
 342       0x20   SPU has tried to execute an invalid instruction.
 343
 344       0x40   SPU has tried to access an invalid channel.
 345
 346       0x3fff0000
 347              The  bits  masked with this value contain the code returned from
 348              stop-and-signal.
 349
 350       There are always one or more of the lower eight bits set  or  an  error
 351       code is returned from spu_run.
 352
 353ERRORS
 354       EAGAIN or EWOULDBLOCK
 355              fd is in non-blocking mode and spu_run would block.
 356
 357       EBADF  fd is not a valid file descriptor.
 358
 359       EFAULT npc is not a valid pointer or status is neither NULL nor a valid
 360              pointer.
 361
 362       EINTR  A signal occurred while spu_run was in progress.  The npc  value
 363              has  been updated to the new program counter value if necessary.
 364
 365       EINVAL fd is not a file descriptor returned from spu_create(2).
 366
 367       ENOMEM Insufficient memory was available to handle a page fault result-
 368              ing from an MFC direct memory access.
 369
 370       ENOSYS the functionality is not provided by the current system, because
 371              either the hardware does not provide SPUs or the spufs module is
 372              not loaded.
 373
 374
 375NOTES
 376       spu_run  is  meant  to  be  used  from  libraries that implement a more
 377       abstract interface to SPUs, not to be used from  regular  applications.
 378       See  http://www.bsc.es/projects/deepcomputing/linuxoncell/ for the rec-
 379       ommended libraries.
 380
 381
 382CONFORMING TO
 383       This call is Linux specific and only implemented by the ppc64 architec-
 384       ture. Programs using this system call are not portable.
 385
 386
 387BUGS
 388       The code does not yet fully implement all features lined out here.
 389
 390
 391AUTHOR
 392       Arnd Bergmann <arndb@de.ibm.com>
 393
 394SEE ALSO
 395       capabilities(7), close(2), spu_create(2), spufs(7)
 396
 397
 398
 399Linux                             2005-09-28                        SPU_RUN(2)
 400
 401------------------------------------------------------------------------------
 402
 403SPU_CREATE(2)              Linux Programmer's Manual             SPU_CREATE(2)
 404
 405
 406
 407NAME
 408       spu_create - create a new spu context
 409
 410
 411SYNOPSIS
 412       #include <sys/types.h>
 413       #include <sys/spu.h>
 414
 415       int spu_create(const char *pathname, int flags, mode_t mode);
 416
 417DESCRIPTION
 418       The  spu_create  system call is used on PowerPC machines that implement
 419       the Cell Broadband Engine Architecture in order to  access  Synergistic
 420       Processor  Units (SPUs). It creates a new logical context for an SPU in
 421       pathname and returns a handle to associated  with  it.   pathname  must
 422       point  to  a  non-existing directory in the mount point of the SPU file
 423       system (spufs).  When spu_create is successful, a directory  gets  cre-
 424       ated on pathname and it is populated with files.
 425
 426       The  returned  file  handle can only be passed to spu_run(2) or closed,
 427       other operations are not defined on it. When it is closed, all  associ-
 428       ated  directory entries in spufs are removed. When the last file handle
 429       pointing either inside  of  the  context  directory  or  to  this  file
 430       descriptor is closed, the logical SPU context is destroyed.
 431
 432       The  parameter flags can be zero or any bitwise or'd combination of the
 433       following constants:
 434
 435       SPU_RAWIO
 436              Allow mapping of some of the hardware registers of the SPU  into
 437              user space. This flag requires the CAP_SYS_RAWIO capability, see
 438              capabilities(7).
 439
 440       The mode parameter specifies the permissions used for creating the  new
 441       directory  in  spufs.   mode is modified with the user's umask(2) value
 442       and then used for both the directory and the files contained in it. The
 443       file permissions mask out some more bits of mode because they typically
 444       support only read or write access. See stat(2) for a full list  of  the
 445       possible mode values.
 446
 447
 448RETURN VALUE
 449       spu_create  returns a new file descriptor. It may return -1 to indicate
 450       an error condition and set errno to  one  of  the  error  codes  listed
 451       below.
 452
 453
 454ERRORS
 455       EACCESS
 456              The  current  user does not have write access on the spufs mount
 457              point.
 458
 459       EEXIST An SPU context already exists at the given path name.
 460
 461       EFAULT pathname is not a valid string pointer in  the  current  address
 462              space.
 463
 464       EINVAL pathname is not a directory in the spufs mount point.
 465
 466       ELOOP  Too many symlinks were found while resolving pathname.
 467
 468       EMFILE The process has reached its maximum open file limit.
 469
 470       ENAMETOOLONG
 471              pathname was too long.
 472
 473       ENFILE The system has reached the global open file limit.
 474
 475       ENOENT Part of pathname could not be resolved.
 476
 477       ENOMEM The kernel could not allocate all resources required.
 478
 479       ENOSPC There  are  not  enough  SPU resources available to create a new
 480              context or the user specific limit for the number  of  SPU  con-
 481              texts has been reached.
 482
 483       ENOSYS the functionality is not provided by the current system, because
 484              either the hardware does not provide SPUs or the spufs module is
 485              not loaded.
 486
 487       ENOTDIR
 488              A part of pathname is not a directory.
 489
 490
 491
 492NOTES
 493       spu_create  is  meant  to  be used from libraries that implement a more
 494       abstract interface to SPUs, not to be used from  regular  applications.
 495       See  http://www.bsc.es/projects/deepcomputing/linuxoncell/ for the rec-
 496       ommended libraries.
 497
 498
 499FILES
 500       pathname must point to a location beneath the mount point of spufs.  By
 501       convention, it gets mounted in /spu.
 502
 503
 504CONFORMING TO
 505       This call is Linux specific and only implemented by the ppc64 architec-
 506       ture. Programs using this system call are not portable.
 507
 508
 509BUGS
 510       The code does not yet fully implement all features lined out here.
 511
 512
 513AUTHOR
 514       Arnd Bergmann <arndb@de.ibm.com>
 515
 516SEE ALSO
 517       capabilities(7), close(2), spu_run(2), spufs(7)
 518
 519
 520
 521Linux                             2005-09-28                     SPU_CREATE(2)
 522
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