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man:spufs

SPUFS(7) Linux Programmer's Manual SPUFS(7)

NAME

     spufs - SPU filesystem

DESCRIPTION

     The  SPU filesystem is used on PowerPC machines that implement the Cell
     Broadband Engine Architecture in order to access Synergistic  Processor
     Units (SPUs).
     The  filesystem provides a name space similar to POSIX shared memory or
     message queues.  Users that have write permissions  on  the  filesystem
     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 sys-
     tem  calls like read(2) or write(2), but often support only a subset of
     the operations supported on regular filesystems.  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) opera-
     tions, 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  debug-
                   ging.
            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 nor-
            mal 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 be  used
            only  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 mes-
                   sage), 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 simi-
            lar 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) when-
                   ever 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--that is, 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 - valid only 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 descrip-
                   tor 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_CRE-
                   ATE_NOSCHED flag.
     /fpcr  This file provides access to the Floating Point Status and  Con-
            trol  Register  (fcpr)  as a binary, four-byte file.  The opera-
            tions 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 noti-
                   fication 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  con-
                   tents  of  the signal1_type or signal2_type files respec-
                   tively.
     /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  hard-
            ware  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 descrip-
                   tor 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 mail-
            boxes 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  mes-
            sages,  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.  Read-
            ing from the file returns the contents of the SPU's MFC Tag Sta-
            tus 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_NON-
                   BLOCK), then the read will block until a DMA tag (as per-
                   formed by a previous write) is complete.  In  nonblocking
                   mode,  the MFC tag status register will be returned with-
                   out 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 Synchroniza-
                   tion (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  sup-
                   ported.
     /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, applica-
                   tions can set the object ID of the SPU context.  Any pre-
                   vious 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 4.16 of the Linux  man-pages  project.   A
     description  of  the project, information about reporting bugs, and the
     latest    version    of    this    page,    can     be     found     at
     https://www.kernel.org/doc/man-pages/.

Linux 2017-09-15 SPUFS(7)

/data/webs/external/dokuwiki/data/pages/man/spufs.txt · Last modified: 2019/05/17 09:47 by 127.0.0.1

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