Provided by: manpages_3.35-0.1ubuntu1_all bug

NAME

       spufs - SPU file system

DESCRIPTION

       The  SPU  file system is used on PowerPC machines that implement the Cell Broadband Engine
       Architecture in order to access Synergistic Processor Units (SPUs).

       The file system provides a name space similar to POSIX shared memory  or  message  queues.
       Users  that  have  write permissions on the file system can use spu_create(2) to establish
       SPU contexts under the spufs root directory.

       Every SPU context is represented by a directory containing  a  predefined  set  of  files.
       These  files  can be used for manipulating the state of the logical SPU.  Users can change
       permissions on the files, but can't add or remove files.

   Mount Options
       uid=<uid>
              Set the user owning the mount point; the default is 0 (root).

       gid=<gid>
              Set the group owning the mount point; the default is 0 (root).

       mode=<mode>
              Set the mode of the top-level directory in spufs, as an  octal  mode  string.   The
              default is 0775.

   Files
       The  files  in  spufs  mostly  follow  the standard behavior for regular system calls like
       read(2) or write(2), but often support only  a  subset  of  the  operations  supported  on
       regular  file systems.  This list details the supported operations and the deviations from
       the standard behavior described in the respective man pages.

       All files that support the read(2) operation also support  readv(2)  and  all  files  that
       support  the  write(2)  operation also support writev(2).  All files support the access(2)
       and stat(2) family of operations, but for the latter call, the only fields of the returned
       stat  structure  that  contain  reliable  information  are  st_mode, st_nlink, st_uid, and
       st_gid.

       All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2) operations, but  will  not
       be able to grant permissions that contradict the possible operations (e.g., read access on
       the wbox file).

       The current set of files is:

       /capabilities
              Contains a  comma-delimited  string  representing  the  capabilities  of  this  SPU
              context.  Possible capabilities are:

              sched  This context may be scheduled.

              step   This context can be run in single-step mode, for debugging.

              New capabilities flags may be added in the future.

       /mem   the  contents  of the local storage memory of the SPU.  This can be accessed like a
              regular shared memory file and contains both code and data in the address space  of
              the SPU.  The possible operations on an open mem file are:

              read(2), pread(2), write(2), pwrite(2), lseek(2)
                     These  operate  as  usual,  with  the exception that lseek(2), write(2), and
                     pwrite(2) are not supported beyond the end of the file.  The  file  size  is
                     the size of the local storage of the SPU, which is normally 256 kilobytes.

              mmap(2)
                     Mapping  mem into the process address space provides access to the SPU local
                     storage within the process address  space.   Only  MAP_SHARED  mappings  are
                     allowed.

       /regs  Contains  the  saved  general-purpose  registers  of  the  SPU  context.  This file
              contains the 128-bit values of each register, from register 0 to register  127,  in
              order.  This allows the general-purpose registers to be inspected for debugging.

              Reading to or writing from this file requires that the context is scheduled out, so
              use of this file is not recommended in normal program operation.

              The regs file  is  not  present  on  contexts  that  have  been  created  with  the
              SPU_CREATE_NOSCHED flag.

       /mbox  The first SPU-to-CPU communication mailbox.  This file is read-only and can be read
              in units of 4 bytes.  The file can only be used in nonblocking mode - even  poll(2)
              cannot  be used to block on this file.  The only possible operation on an open mbox
              file is:

              read(2)
                     If count is smaller than four, read(2) returns -1 and sets errno to  EINVAL.
                     If  there  is no data available in the mailbox (i.e., the SPU has not sent a
                     mailbox message), the return value is set to -1 and errno is set to  EAGAIN.
                     When  data  has  been  read  successfully, four bytes are placed in the data
                     buffer and the value four is returned.

       /ibox  The second SPU-to-CPU communication mailbox.  This file is  similar  to  the  first
              mailbox file, but can be read in blocking I/O mode, thus calling read(2) on an open
              ibox file will block until the SPU  has  written  data  to  its  interrupt  mailbox
              channel  (unless  the  file  has  been  opened  with O_NONBLOCK, see below).  Also,
              poll(2) and similar system calls can be used to monitor for the presence of mailbox
              data.

              The possible operations on an open ibox file are:

              read(2)
                     If  count is smaller than four, read(2) returns -1 and sets errno to EINVAL.
                     If there is no data available in the mailbox and  the  file  descriptor  has
                     been  opened with O_NONBLOCK, the return value is set to -1 and errno is set
                     to EAGAIN.

                     If there is no data available in the mailbox and  the  file  descriptor  has
                     been  opened without O_NONBLOCK, the call will block until the SPU writes to
                     its interrupt mailbox channel.  When data has been read  successfully,  four
                     bytes are placed in the data buffer and the value four is returned.

              poll(2)
                     Poll  on  the  ibox  file  returns  (POLLIN  |  POLLRDNORM) whenever data is
                     available for reading.

       /wbox  The CPU-to-SPU communication mailbox.  It is write-only and can be written in units
              of  four  bytes.   If  the mailbox is full, write(2) will block, and poll(2) can be
              used to block until the mailbox is  available  for  writing  again.   The  possible
              operations on an open wbox file are:

              write(2)
                     If count is smaller than four, write(2) returns -1 and sets errno to EINVAL.
                     If there is no space available in the mailbox and the  file  descriptor  has
                     been  opened with O_NONBLOCK, the return value is set to -1 and errno is set
                     to EAGAIN.

                     If there is no space available in the mailbox and the  file  descriptor  has
                     been opened without O_NONBLOCK, the call will block until the SPU reads from
                     its PPE (PowerPC Processing Element) mailbox channel.  When  data  has  been
                     written successfully, the system call returns four as its function result.

              poll(2)
                     A  poll  on  the  wbox file returns (POLLOUT | POLLWRNORM) whenever space is
                     available for writing.

       /mbox_stat, /ibox_stat, /wbox_stat
              These are read-only files that contain the length of  the  current  queue  of  each
              mailbox,  i.e.,  how many words can be read from mbox or ibox or how many words can
              be written to wbox without blocking.  The files can be read only in four-byte units
              and  return  a big-endian binary integer number.  The only possible operation on an
              open *box_stat file is:

              read(2)
                     If count is smaller than four, read(2) returns -1 and sets errno to  EINVAL.
                     Otherwise,  a  four-byte  value is placed in the data buffer.  This value is
                     the number of elements that can be read from (for mbox_stat  and  ibox_stat)
                     or  written  to  (for  wbox_stat) the respective mailbox without blocking or
                     returning an EAGAIN error.

       /npc, /decr, /decr_status, /spu_tag_mask, /event_mask, /event_status, /srr0, /lslr
              Internal registers of the SPU.  These files contain an  ASCII  string  representing
              the  hex  value of the specified register.  Reads and writes on these files (except
              for npc, see below) require that the SPU context  be  scheduled  out,  so  frequent
              access to these files is not recommended for normal program operation.

              The contents of these files are:

              npc             Next  Program  Counter  -  only  valid when the SPU is in a stopped
                              state.

              decr            SPU Decrementer

              decr_status     Decrementer Status

              spu_tag_mask    MFC tag mask for SPU DMA

              event_mask      Event mask for SPU interrupts

              event_status    Number of SPU events pending (read-only)

              srr0            Interrupt Return address register

              lslr            Local Store Limit Register

              The possible operations on these files are:

              read(2)
                     Reads the current register value.  If the register value is larger than  the
                     buffer  passed  to  the  read(2) system call, subsequent reads will continue
                     reading from the same buffer, until the end of the buffer is reached.

                     When a complete string has been read, all subsequent  read  operations  will
                     return zero bytes and a new file descriptor needs to be opened to read a new
                     value.

              write(2)
                     A write(2) operation on the file sets the register to the value given in the
                     string.   The string is parsed from the beginning until the first nonnumeric
                     character or the end of the buffer.  Subsequent  writes  to  the  same  file
                     descriptor overwrite the previous setting.

                     Except  for  the npc file, these files are not present on contexts that have
                     been created with the SPU_CREATE_NOSCHED flag.

       /fpcr  This file provides access to the Floating Point Status and Control Register  (fcpr)
              as a binary, four-byte file.  The operations on the fpcr file are:

              read(2)
                     If  count is smaller than four, read(2) returns -1 and sets errno to EINVAL.
                     Otherwise, a four-byte value is placed in  the  data  buffer;  this  is  the
                     current value of the fpcr register.

              write(2)
                     If count is smaller than four, write(2) returns -1 and sets errno to EINVAL.
                     Otherwise, a four-byte value is copied from the data  buffer,  updating  the
                     value of the fpcr register.

       /signal1, /signal2
              The  files provide access to the two signal notification channels of an SPU.  These
              are read-write files that operate on four-byte words.   Writing  to  one  of  these
              files  triggers an interrupt on the SPU.  The value written to the signal files can
              be read from the SPU through a channel read or from host  user  space  through  the
              file.  After the value has been read by the SPU, it is reset to zero.  The possible
              operations on an open signal1 or signal2 file are:

              read(2)
                     If count is smaller than four, read(2) returns -1 and sets errno to  EINVAL.
                     Otherwise,  a  four-byte  value  is  placed  in the data buffer; this is the
                     current value of the specified signal notification register.

              write(2)
                     If count is smaller than four, write(2) returns -1 and sets errno to EINVAL.
                     Otherwise,  a  four-byte  value is copied from the data buffer, updating the
                     value  of  the  specified  signal   notification   register.    The   signal
                     notification register will either be replaced with the input data or will be
                     updated to the bitwise OR operation of the old value  and  the  input  data,
                     depending  on  the  contents  of  the  signal1_type  or  signal2_type  files
                     respectively.

       /signal1_type, /signal2_type
              These two files change the behavior of the signal1 and signal2 notification  files.
              They  contain a numeric ASCII string which is read as either "1" or "0".  In mode 0
              (overwrite), the hardware replaces the contents of the signal channel with the data
              that  is  written to it.  In mode 1 (logical OR), the hardware accumulates the bits
              that  are  subsequently  written  to  it.   The  possible  operations  on  an  open
              signal1_type or signal2_type file are:

              read(2)
                     When  the  count  supplied  to the read(2) call is shorter than the required
                     length for the digit (plus a newline character), subsequent reads  from  the
                     same  file  descriptor will complete the string.  When a complete string has
                     been read, all subsequent read operations will return zero bytes and  a  new
                     file descriptor needs to be opened to read the value again.

              write(2)
                     A write(2) operation on the file sets the register to the value given in the
                     string.  The string is parsed from the beginning until the first  nonnumeric
                     character  or  the  end  of  the buffer.  Subsequent writes to the same file
                     descriptor overwrite the previous setting.

       /mbox_info, /ibox_info, /wbox_info, /dma_into, /proxydma_info
              Read-only files that contain the saved state of the SPU mailboxes and  DMA  queues.
              This  allows  the  SPU status to be inspected, mainly for debugging.  The mbox_info
              and ibox_info files each contain  the  four-byte  mailbox  message  that  has  been
              written  by  the  SPU.   If  no  message  has been written to these mailboxes, then
              contents of these files is undefined.  The mbox_stat, ibox_stat and wbox_stat files
              contain the available message count.

              The wbox_info file contains an array of four-byte mailbox messages, which have been
              sent to the SPU.  With current CBEA machines, the array is four items in length, so
              up  to  4 * 4 = 16 bytes can be read from this file.  If any mailbox queue entry is
              empty, then the bytes read at the corresponding location are undefined.

              The dma_info file contains the contents of the SPU MFC DMA  queue,  represented  as
              the following structure:

                  struct spu_dma_info {
                      uint64_t         dma_info_type;
                      uint64_t         dma_info_mask;
                      uint64_t         dma_info_status;
                      uint64_t         dma_info_stall_and_notify;
                      uint64_t         dma_info_atomic_command_status;
                      struct mfc_cq_sr dma_info_command_data[16];
                  };

              The  last  member  of  this  data  structure is the actual DMA queue, containing 16
              entries.  The mfc_cq_sr structure is defined as:

                  struct mfc_cq_sr {
                      uint64_t mfc_cq_data0_RW;
                      uint64_t mfc_cq_data1_RW;
                      uint64_t mfc_cq_data2_RW;
                      uint64_t mfc_cq_data3_RW;
                  };

              The proxydma_info file contains similar information, but describes  the  proxy  DMA
              queue  (i.e.,  DMAs initiated by entities outside the SPU) instead.  The file is in
              the following format:

                  struct spu_proxydma_info {
                      uint64_t         proxydma_info_type;
                      uint64_t         proxydma_info_mask;
                      uint64_t         proxydma_info_status;
                      struct mfc_cq_sr proxydma_info_command_data[8];
                  };

              Accessing these files requires that the SPU context is scheduled out - frequent use
              can be inefficient.  These files should not be used for normal program operation.

              These  files  are  not  present  on  contexts  that  have  been  created  with  the
              SPU_CREATE_NOSCHED flag.

       /cntl  This file provides access to the SPU Run Control and SPU status  registers,  as  an
              ASCII string.  The following operations are supported:

              read(2)
                     Reads  from  the cntl file will return an ASCII string with the hex value of
                     the SPU Status register.

              write(2)
                     Writes to the cntl file will set the context's SPU Run Control register.

       /mfc   Provides access to the Memory Flow Controller of the SPU.  Reading  from  the  file
              returns  the contents of the SPU's MFC Tag Status register, and writing to the file
              initiates a DMA from the MFC.  The following operations are supported:

              write(2)
                     Writes to this file need to be in the format of a MFC DMA  command,  defined
                     as follows:

                         struct mfc_dma_command {
                             int32_t  pad;    /* reserved */
                             uint32_t lsa;    /* local storage address */
                             uint64_t ea;     /* effective address */
                             uint16_t size;   /* transfer size */
                             uint16_t tag;    /* command tag */
                             uint16_t class;  /* class ID */
                             uint16_t cmd;    /* command opcode */
                         };

                     Writes  are  required  to be exactly sizeof(struct mfc_dma_command) bytes in
                     size.  The command will be sent to the SPU's MFC proxy queue,  and  the  tag
                     stored in the kernel (see below).

              read(2)
                     Reads  the  contents  of  the tag status register.  If the file is opened in
                     blocking mode (i.e., without O_NONBLOCK), then the read will block  until  a
                     DMA  tag  (as  performed  by  a previous write) is complete.  In nonblocking
                     mode, the MFC tag status register will be returned without waiting.

              poll(2)
                     Calling poll(2) on the mfc file will block until a new DMA  can  be  started
                     (by checking for POLLOUT) or until a previously started DMA (by checking for
                     POLLIN) has been completed.

                     /mss Provides access to the MFC MultiSource Synchronization (MSS)  facility.
                     By mmap(2)-ing this file, processes can access the MSS area of the SPU.

                     The following operations are supported:

              mmap(2)
                     Mapping  mss into the process address space gives access to the SPU MSS area
                     within the process address space.  Only MAP_SHARED mappings are allowed.

       /psmap Provides access to the whole problem-state mapping of the  SPU.   Applications  can
              use  this  area to interface to the SPU, rather than writing to individual register
              files in spufs.

              The following operations are supported:

              mmap(2)
                     Mapping psmap gives a process a direct map of the SPU  problem  state  area.
                     Only MAP_SHARED mappings are supported.

       /phys-id
              Read-only  file  containing the physical SPU number that the SPU context is running
              on.  When the context is not running, this file contains the string "-1".

              The physical SPU number is given by an ASCII hex string.

       /object-id
              Allows applications to store (or retrieve) a single 64-bit  ID  into  the  context.
              This ID is later used by profiling tools to uniquely identify the context.

              write(2)
                     By  writing  an  ASCII  hex  value  into this file, applications can set the
                     object ID of the SPU context.  Any  previous  value  of  the  object  ID  is
                     overwritten.

              read(2)
                     Reading  this  file gives an ASCII hex string representing the object ID for
                     this SPU context.

EXAMPLE

       /etc/fstab  entry
              none      /spu      spufs     gid=spu   0    0

SEE ALSO

       close(2),  spu_create(2),  spu_run(2),  capabilities(7),   The   Cell   Broadband   Engine
       Architecture (CBEA) specification

COLOPHON

       This  page  is  part of release 3.35 of the Linux man-pages project.  A description of the
       project, and information about reporting bugs, can be found at  http://man7.org/linux/man-
       pages/.