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1 SPUFS(2) Linux Programmer's Manual SPUFS(2) 2 3 4 5 NAME 6 spufs - the SPU file system 7 8 9 DESCRIPTION 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 24 MOUNT 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 32 FILES 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. 260 261 262 EXAMPLES 263 /etc/fstab entry 264 none /spu spufs gid=spu 0 0 265 266 267 AUTHORS 268 Arnd Bergmann <firstname.lastname@example.org>, Mark Nutter <email@example.com>, 269 Ulrich Weigand <Ulrich.Weigand@de.ibm.com> 270 271 SEE ALSO 272 capabilities(7), close(2), spu_create(2), spu_run(2), spufs(7) 273 274 275 276 Linux 2005-09-28 SPUFS(2) 277 278 ------------------------------------------------------------------------------ 279 280 SPU_RUN(2) Linux Programmer's Manual SPU_RUN(2) 281 282 283 284 NAME 285 spu_run - execute an spu context 286 287 288 SYNOPSIS 289 #include <sys/spu.h> 290 291 int spu_run(int fd, unsigned int *npc, unsigned int *event); 292 293 DESCRIPTION 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. 326 327 RETURN 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. 352 353 ERRORS 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. 373 374 375 NOTES 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. 380 381 382 CONFORMING TO 383 This call is Linux specific and only implemented by the ppc64 architec- 384 ture. Programs using this system call are not portable. 385 386 387 BUGS 388 The code does not yet fully implement all features lined out here. 389 390 391 AUTHOR 392 Arnd Bergmann <firstname.lastname@example.org> 393 394 SEE ALSO 395 capabilities(7), close(2), spu_create(2), spufs(7) 396 397 398 399 Linux 2005-09-28 SPU_RUN(2) 400 401 ------------------------------------------------------------------------------ 402 403 SPU_CREATE(2) Linux Programmer's Manual SPU_CREATE(2) 404 405 406 407 NAME 408 spu_create - create a new spu context 409 410 411 SYNOPSIS 412 #include <sys/types.h> 413 #include <sys/spu.h> 414 415 int spu_create(const char *pathname, int flags, mode_t mode); 416 417 DESCRIPTION 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. 446 447 448 RETURN 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. 452 453 454 ERRORS 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. 489 490 491 492 NOTES 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. 497 498 499 FILES 500 pathname must point to a location beneath the mount point of spufs. By 501 convention, it gets mounted in /spu. 502 503 504 CONFORMING TO 505 This call is Linux specific and only implemented by the ppc64 architec- 506 ture. Programs using this system call are not portable. 507 508 509 BUGS 510 The code does not yet fully implement all features lined out here. 511 512 513 AUTHOR 514 Arnd Bergmann <email@example.com> 515 516 SEE ALSO 517 capabilities(7), close(2), spu_run(2), spufs(7) 518 519 520 521 Linux 2005-09-28 SPU_CREATE(2)