.\" This is _*_ nroff _*_ source. Emacs, gimme all those colors :) .\" .\" Copyright (c) International Business Machines  Corp., 2006 .\" .\" This program is free software;  you can redistribute it and/or .\" modify it under the terms of the GNU General Public License as .\" published by the Free Software Foundation; either version 2 of .\" the License, or (at your option) any later version. .\" .\" This program is distributed in the hope that it will be useful, .\" but WITHOUT ANY WARRANTY;  without even the implied warranty of .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See .\" the GNU General Public License for more details. .\" .\" You should have received a copy of the GNU General Public License .\" along with this program;  if not, write to the Free Software .\" Foundation, Inc., 59 Temple Place, Suite 330, Boston, .\" MA 02111-1307 USA .\" .\" HISTORY: .\" 2005-09-28, created by Arnd Bergmann , .\" Mark Nutter and .\" Ulrich Weigand .\" 2006-06-16, revised by Eduardo M. Fleury .\" 2007-07-10, quite a lot of polishing by mtk .\" .TH SPUFS 7 2007-07-10 "Linux" "Linux Programmer's Manual" .SH NAME spufs \- the SPU file system .SH 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 .BR 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 those files, but can't add or remove files. .SS Mount Options .TP .B uid= set the user owning the mount point; the default is 0 (root). .TP .B gid= set the group owning the mount point; the default is 0 (root). .SS Files The files in .I spufs mostly follow the standard behavior for regular system calls like .BR read (2) or .BR 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 .BR read (2) operation also support .BR readv (2) and all files that support the .BR write (2) operation also support .BR writev (2). All files support the .BR access (2) and .BR stat (2) family of operations, but for the latter call, the only fields of the returned .I stat structure that contain reliable information are .IR st_mode , .IR st_nlink , .IR st_uid , and .IR st_gid . All files support the .BR chmod (2)/ fchmod (2) and .BR chown (2)/ fchown (2) operations, but will not be able to grant permissions that contradict the possible operations (e.g., read access on the .I wbox file). The current set of files is: .TP .B /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 .I mem file are: .RS .TP .BR read "(2), " pread "(2), " write "(2), " pwrite "(2), " lseek (2) These operate as usual, with the exception that .BR seek "(2), " write (2) and .BR 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. .TP .BR mmap (2) Mapping .I mem into the process address space provides access to the SPU local storage within the process address space. Only .B MAP_SHARED mappings are allowed. .RE .TP .B /mbox The first SPU-to-CPU communication mailbox. This file is read-only and can be read in units of 32 bits. The file can only be used in non-blocking mode and not even .BR poll (2) will block on it. The only possible operation on an open .I mbox file is: .RS .TP .BR read (2) If .I count is smaller than four, .BR read (2) returns \-1 and sets .I errno to .BR EINVAL . If there is no data available in the mailbox, the return value is set to \-1 and .I errno is set to .BR EAGAIN . When data has been read successfully, four bytes are placed in the data buffer and the value four is returned. .RE .TP .B /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 .BR poll (2) and similar system calls can be used to monitor this file. The possible operations on an open .I ibox file are: .RS .TP .BR read (2) If .I count is smaller than four, .BR read (2) returns \-1 and sets .I errno to .BR EINVAL . If there is no data available in the mailbox and the file descriptor has been opened with .BR O_NONBLOCK , the return value is set to \-1 and .I errno is set to .BR EAGAIN . If there is no data available in the mailbox and the file descriptor has been opened without .BR 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. .TP .BR poll (2) Poll on the .I ibox file returns .I "(POLLIN | POLLRDNORM)" whenever data is available for reading. .RE .TP .B /wbox The CPU-to-SPU communication mailbox. It is write-only and can be written in units of 32 bits. If the mailbox is full, .BR write (2) will block and .BR poll (2) can be used to wait for it to become empty again. The possible operations on an open .I wbox file are: .RS .TP .BR write (2) If .I count is smaller than four, .BR write (2) returns \-1 and sets .I errno to .BR EINVAL . If there is no space available in the mailbox and the file descriptor has been opened with .BR O_NONBLOCK , the return value is set to \-1 and .I errno is set to .BR EAGAIN . If there is no space available in the mailbox and the file descriptor has been opened without .BR O_NONBLOCK , the call will block until the SPU reads from its PPE mailbox channel. When data has been written successfully, the system call returns four as its function result. .TP .BR poll (2) A poll on the .I wbox file returns .I "(POLLOUT | POLLWRNORM)" whenever space is available for writing. .RE .TP .BR /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 .IR mbox " or " ibox or how many words can be written to .I wbox without blocking. The files can be read only in four-byte units and return a big-endian binary integer number. The possible operations on an open .I *box_stat file are: .RS .TP .BR read (2) If .I count is smaller than four, .BR read (2) returns \-1 and sets .I errno to .BR 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 .I mbox_stat and .IR ibox_stat ) or written to (for .IR wbox_stat ) the respective mailbox without blocking or getting an .BR EAGAIN error. .RE .TP .BR /npc ", " /decr ", " /decr_status ", " /spu_tag_mask ", " \ /event_mask ", " /srr0 These files expose internal registers of the SPU. The values are represented as ASCII strings containing the numeric value of each register. These can be used in read/write mode for debugging, but normal operation of programs should not rely on these files because accesses to any of them except .I npc require an SPU context save, which is very inefficient. .IP The contents of these files are: .RS .TP 16 .I npc Next Program Counter .TP .I decr SPU Decrementer .TP .I decr_status Decrementer Status .TP .I spu_tag_mask MFC tag mask for SPU DMA .TP .I event_mask Event mask for SPU interrupts .TP .I srr0 Interrupt Return address register .RE .IP The possible operations on one of these files are: .RS .TP .BR read (2) When the .I count supplied to the .BR read (2) call is shorter than the required length for the register value plus a newline character, subsequent reads from the same file descriptor will complete the string, regardless of changes to the register by a running SPU task. 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. .TP .BR write (2) A .BR 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 non-numeric character or the end of the buffer. Subsequent writes to the same file descriptor overwrite the previous setting. .RE .TP .B /fpcr This file provides access to the Floating Point Status and Control Register as a four-byte file. The operations on the .I fpcr file are: .RS .TP .BR read (2) If .I count is smaller than four, .BR read (2) returns \-1 and sets .I errno to .BR EINVAL . Otherwise, a four-byte value is placed in the data buffer; this is the current value of the .I fpcr register. .TP .BR write (2) If .I count is smaller than four, .BR write (2) returns \-1 and sets .I errno to .BR EINVAL . Otherwise, a four-byte value is copied from the data buffer, updating the value of the .I fpcr register. .RE .TP .BR /signal1 ", " /signal2 The files provide access to the two signal notification channels of an SPU. These are read-write files that operate on 32-bit 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 .I signal1 or .I signal2 file are: .RS .TP .BR read (2) If .I count is smaller than four, .BR read (2) returns \-1 and sets .I errno to .BR EINVAL . Otherwise, a four-byte value is placed in the data buffer; this is the current value of the specified signal notification register. .TP .BR write (2) If .I count is smaller than four, .BR write (2) returns \-1 and sets .I errno to .BR 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 .IR signal1_type or .IR signal2_type files respectively. .RE .TP .BR /signal1_type ", " /signal2_type These two files change the behavior of the .IR signal1 and .I signal2 notification files. They contain a numerical 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 .I signal1_type or .I signal2_type file are: .RS .TP .BR read (2) When the count supplied to the .BR 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. .TP .BR write (2) A .BR 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 non-numeric character or the end of the buffer. Subsequent writes to the same file descriptor overwrite the previous setting. .RE .SH EXAMPLE .TP .IR /etc/fstab " entry" none /spu spufs gid=spu 0 0 .\" .SH AUTHORS .\" Arnd Bergmann , .\" Mark Nutter and .\" Ulrich Weigand .SH SEE ALSO .BR close (2), .BR spu_create (2), .BR spu_run (2)