spu_create(2)

NAME
spu_create - create a new spu context

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS
#include <sys/spu.h>          /* Definition of SPU_* constants */
#include <sys/syscall.h>      /* Definition of SYS_* constants */
#include <unistd.h>

int syscall(SYS_spu_create, const char *pathname, unsigned int flags,
            mode_t mode, int neighbor_fd);

Note: glibc provides no wrapper for spu_create(), necessitating the use of syscall(2).

DESCRIPTION
The spu_create() system call is used on PowerPC machines that implement the Cell Broadband Engine Architecture in order to access Synergistic Processor Units (SPUs). It creates a new logical context for an SPU in pathname and returns a file descriptor associated with it. pathname must refer to a nonexistent directory in the mount point of the SPU filesystem (spufs). If spu_create() is successful, a directory is created at pathname and it is populated with the files described in spufs(7).

When a context is created, the returned file descriptor can only be passed to spu_run(2), used as the dirfd argument to the *at family of system calls (e.g., openat(2)), or closed; other operations are not defined. A logical SPU context is destroyed (along with all files created within the context's pathname directory) once the last reference to the context has gone; this usually occurs when the file descriptor returned by spu_create() is closed.

The mode argument (minus any bits set in the process's umask(2)) specifies the permissions used for creating the new directory in spufs. See stat(2) for a full list of the possible mode values.

The neighbor_fd is used only when the SPU_CREATE_AFFINITY_SPU flag is specified; see below.

The flags argument can be zero or any bitwise OR-ed combination of the following constants:

SPU_CREATE_EVENTS_ENABLED
    Rather than using signals for reporting DMA errors, use the event argument to spu_run(2).

SPU_CREATE_GANG
    Create an SPU gang instead of a context. (A gang is a group of SPU contexts that are functionally related to each other and which share common scheduling parameters—priority and policy. In the future, gang scheduling may be implemented causing the group to be switched in and out as a single unit.)

    A new directory will be created at the location specified by the pathname argument. This gang may be used to hold other SPU contexts, by providing a pathname that is within the gang directory to further calls to spu_create().

SPU_CREATE_NOSCHED
    Create a context that is not affected by the SPU scheduler. Once the context is run, it will not be scheduled out until it is destroyed by the creating process.

    Because the context cannot be removed from the SPU, some functionality is disabled for SPU_CREATE_NOSCHED contexts. Only a subset of the files will be available in this context directory in spufs. Additionally, SPU_CREATE_NOSCHED contexts cannot dump a core file when crashing.

    Creating SPU_CREATE_NOSCHED contexts requires the CAP_SYS_NICE capability.

SPU_CREATE_ISOLATE
    Create an isolated SPU context. Isolated contexts are protected from some PPE (PowerPC Processing Element) operations, such as access to the SPU local store and the NPC register.

    Creating SPU_CREATE_ISOLATE contexts also requires the SPU_CREATE_NOSCHED flag.

SPU_CREATE_AFFINITY_SPU (since Linux 2.6.23)
    Create a context with affinity to another SPU context. This affinity information is used within the SPU scheduling algorithm. Using this flag requires that a file descriptor referring to the other SPU context be passed in the neighbor_fd argument.

SPU_CREATE_AFFINITY_MEM (since Linux 2.6.23)
    Create a context with affinity to system memory. This affinity information is used within the SPU scheduling algorithm.

RETURN VALUE
On success, spu_create() returns a new file descriptor. On failure, -1 is returned, and errno is set to indicate the error.

ERRORS

EACCES
    The current user does not have write access to the spufs(7) mount point.

EEXIST
    An SPU context already exists at the given pathname.

EFAULT
    pathname is not a valid string pointer in the calling process's address space.

EINVAL
    pathname is not a directory in the spufs(7) mount point, or invalid flags have been provided.

ELOOP
    Too many symbolic links were found while resolving pathname.

EMFILE
    The per-process limit on the number of open file descriptors has been reached.

ENAMETOOLONG
    pathname is too long.

ENFILE
    The system-wide limit on the total number of open files has been reached.

ENODEV
    An isolated context was requested, but the hardware does not support SPU isolation.

ENOENT
    Part of pathname could not be resolved.

ENOMEM
    The kernel could not allocate all resources required.

ENOSPC
    There are not enough SPU resources available to create a new context or the user-specific limit for the number of SPU contexts has been reached.

ENOSYS
    The functionality is not provided by the current system, because either the hardware does not provide SPUs or the spufs module is not loaded.

ENOTDIR
    A part of pathname is not a directory.

EPERM
    The SPU_CREATE_NOSCHED flag has been given, but the user does not have the CAP_SYS_NICE capability.

FILES
pathname must point to a location beneath the mount point of spufs. By convention, it gets mounted in /spu.

STANDARDS
Linux on PowerPC.

HISTORY
Linux 2.6.16.

Prior to the addition of the SPU_CREATE_AFFINITY_SPU flag in Linux 2.6.23, the spu_create() system call took only three arguments (i.e., there was no neighbor_fd argument).

NOTES
spu_create() is meant to be used from libraries that implement a more abstract interface to SPUs, not to be used from regular applications. See http://www.bsc.es/projects/deepcomputing/linuxoncell/ for the recommended libraries.

EXAMPLES
See spu_run(2) for an example of the use of spu_create()

SEE ALSO
close(2), spu_run(2), capabilities(7), spufs(7)