man2/spu_create.2

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.\" HISTORY:
.\" 2005-09-28, created by Arnd Bergmann <arndb@de.ibm.com>
.\" 2006-06-16, revised by Eduardo M. Fleury <efleury@br.ibm.com>
.\" 2007-07-10, some polishing by mtk
.\" 2007-09-28, updates for newer kernels by Jeremy Kerr <jk@ozlabs.org>
.\"
.TH SPU_CREATE 2 2021-03-22 Linux "Linux Programmer's Manual"
.SH NAME
spu_create \- create a new spu context
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <sys/spu.h>
.PP
.BI "int spu_create(const char *" pathname ", unsigned int " flags \
", mode_t " mode ,
.BI "               int " neighbor_fd ");"
.fi
.PP
.IR Note :
There is no glibc wrapper for this system call; see NOTES.
.SH DESCRIPTION
The
.BR 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
.I pathname
and returns a file descriptor associated with it.
.I pathname
must refer to a nonexistent directory in the mount point of
the SPU filesystem
.RB ( spufs ).
If
.BR spu_create ()
is successful, a directory is created at
.I pathname
and it is populated with the files described in
.BR spufs (7).
.PP
When a context is created,
the returned file descriptor can only be passed to
.BR spu_run (2),
used as the
.I dirfd
argument to the
.B *at
family of system calls (e.g.,
.BR openat (2)),
or closed;
other operations are not defined.
A logical SPU
context is destroyed (along with all files created within the context's
.I pathname
directory) once the last reference to the context has gone;
this usually occurs when the file descriptor returned by
.BR spu_create ()
is closed.
.PP
The
.I mode
argument (minus any bits set in the process's
.BR umask (2))
specifies the permissions used for creating the new directory in
.BR spufs .
See
.BR stat (2)
for a full list of the possible
.I mode
values.
.PP
The
.I neighbor_fd
is used only when the
.B SPU_CREATE_AFFINITY_SPU
flag is specified; see below.
.PP
The
.I flags
argument can be zero or any bitwise OR-ed
combination of the following constants:
.TP
.B SPU_CREATE_EVENTS_ENABLED
Rather than using signals for reporting DMA errors, use the
.I event
argument to
.BR spu_run (2).
.TP
.B 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\(empriority and policy.
In the future, gang scheduling may be implemented causing
the group to be switched in and out as a single unit.)
.IP
A new directory will be created at the location specified by the
.I 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
.BR spu_create ().
.TP
.B 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.
.IP
Because the context cannot be removed from the SPU, some functionality
is disabled for
.BR SPU_CREATE_NOSCHED
contexts.
Only a subset of the files will be
available in this context directory in
.BR spufs .
Additionally,
.BR SPU_CREATE_NOSCHED
contexts cannot dump a core file when crashing.
.IP
Creating
.BR SPU_CREATE_NOSCHED
contexts requires the
.B CAP_SYS_NICE
capability.
.TP
.B 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.
.IP
Creating
.B SPU_CREATE_ISOLATE
contexts also requires the
.B SPU_CREATE_NOSCHED
flag.
.TP
.BR SPU_CREATE_AFFINITY_SPU " (since Linux 2.6.23)"
.\" commit 8e68e2f248332a9c3fd4f08258f488c209bd3e0c
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
.I neighbor_fd
argument.
.TP
.BR SPU_CREATE_AFFINITY_MEM " (since Linux 2.6.23)"
.\" commit 8e68e2f248332a9c3fd4f08258f488c209bd3e0c
Create a context with affinity to system memory.
This affinity information
is used within the SPU scheduling algorithm.
.SH RETURN VALUE
On success,
.BR spu_create ()
returns a new file descriptor.
On failure, \-1 is returned, and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EACCES
The current user does not have write access to the
.BR spufs (7)
mount point.
.TP
.B EEXIST
An SPU context already exists at the given pathname.
.TP
.B EFAULT
.I pathname
is not a valid string pointer in the
calling process's address space.
.TP
.B EINVAL
.I pathname
is not a directory in the
.BR spufs (7)
mount point, or invalid flags have been provided.
.TP
.B ELOOP
Too many symbolic links were found while resolving
.IR pathname .
.TP
.B EMFILE
The per-process limit on the number of open file descriptors has been reached.
.TP
.B ENAMETOOLONG
.I pathname
is too long.
.TP
.B ENFILE
The system-wide limit on the total number of open files has been reached.
.TP
.B ENODEV
An isolated context was requested, but the hardware does not support
SPU isolation.
.TP
.B ENOENT
Part of
.I pathname
could not be resolved.
.TP
.B ENOMEM
The kernel could not allocate all resources required.
.TP
.B 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.
.TP
.B 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.
.TP
.B ENOTDIR
A part of
.I pathname
is not a directory.
.TP
.B EPERM
The
.B SPU_CREATE_NOSCHED
flag has been given, but the user does not have the
.B CAP_SYS_NICE
capability.
.SH FILES
.I pathname
must point to a location beneath the mount point of
.BR spufs .
By convention, it gets mounted in
.IR /spu .
.SH VERSIONS
The
.BR spu_create ()
system call was added to Linux in kernel 2.6.16.
.SH CONFORMING TO
This call is Linux-specific and implemented only on the PowerPC
architecture.
Programs using this system call are not portable.
.SH NOTES
Glibc does not provide a wrapper for this system call; call it using
.BR syscall (2).
Note however, that
.BR 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
.UR http://www.bsc.es\:/projects\:/deepcomputing\:/linuxoncell/
.UE
for the recommended libraries.
.PP
Prior to the addition of the
.B SPU_CREATE_AFFINITY_SPU
flag in Linux 2.6.23, the
.BR spu_create ()
system call took only three arguments (i.e., there was no
.I neighbor_fd
argument).
.SH EXAMPLES
See
.BR spu_run (2)
for an example of the use of
.BR spu_create ()
.SH SEE ALSO
.BR close (2),
.BR spu_run (2),
.BR capabilities (7),
.BR spufs (7)