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10 spufs - the SPU file system
16 The SPU file system is used on PowerPC machines that implement the Cell
20 The file system provides a name space similar to posix shared memory or
21 message queues. Users that have write permissions on the file system
22 can use spu_create(2) to establish SPU contexts in the spufs root.
25 set of files. These files can be used for manipulating the state of the
34 set the user owning the mount point, the default is 0 (root).
37 set the group owning the mount point, the default is 0 (root).
43 The files in spufs mostly follow the standard behavior for regular sys-
45 the operations supported on regular file systems. This list details the
46 supported operations and the deviations from the behaviour in the
49 All files that support the read(2) operation also support readv(2) and
50 all files that support the write(2) operation also support writev(2).
51 All files support the access(2) and stat(2) family of operations, but
52 only the st_mode, st_nlink, st_uid and st_gid fields of struct stat
55 All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2) opera-
56 tions, but will not be able to grant permissions that contradict the
57 possible operations, e.g. read access on the wbox file.
59 The current set of files is:
63 the contents of the local storage memory of the SPU. This can be
65 data in the address space of the SPU. The possible operations on an
69 These operate as documented, with the exception that seek(2),
70 write(2) and pwrite(2) are not supported beyond the end of the
71 file. The file size is the size of the local storage of the SPU,
75 Mapping mem into the process address space gives access to the
76 SPU local storage within the process address space. Only
81 The first SPU to CPU communication mailbox. This file is read-only and
82 can be read in units of 32 bits. The file can only be used in non-
83 blocking mode and it even poll() will not block on it. The possible
88 sets errno to EINVAL. If there is no data available in the mail
89 box, the return value is set to -1 and errno becomes EAGAIN.
91 the data buffer and the value four is returned.
95 The second SPU to CPU communication mailbox. This file is similar to
96 the first mailbox file, but can be read in blocking I/O mode, and the
97 poll family of system calls can be used to wait for it. The possible
102 sets errno to EINVAL. If there is no data available in the mail
103 box and the file descriptor has been opened with O_NONBLOCK, the
106 If there is no data available in the mail box and the file
107 descriptor has been opened without O_NONBLOCK, the call will
108 block until the SPU writes to its interrupt mailbox channel.
110 the data buffer and the value four is returned.
113 Poll on the ibox file returns (POLLIN | POLLRDNORM) whenever
118 The CPU to SPU communation mailbox. It is write-only and can be written
119 in units of 32 bits. If the mailbox is full, write() will block and
120 poll can be used to wait for it becoming empty again. The possible
123 is no space available in the mail box and the file descriptor has been
124 opened with O_NONBLOCK, the return value is set to -1 and errno becomes
127 If there is no space available in the mail box and the file descriptor
128 has been opened without O_NONBLOCK, the call will block until the SPU
130 fully, four bytes are placed in the data buffer and the value four is
134 Poll on the ibox file returns (POLLOUT | POLLWRNORM) whenever
139 Read-only files that contain the length of the current queue, i.e. how
141 written to wbox without blocking. The files can be read only in 4-byte
142 units and return a big-endian binary integer number. The possible
148 the data buffer, containing the number of elements that can be
150 wbox_stat) the respective mail box without blocking or resulting
155 Internal registers of the SPU. The representation is an ASCII string
156 with the numeric value of the next instruction to be executed. These
161 The contents of these files are:
173 The possible operations on an open npc, decr, decr_status,
177 When the count supplied to the read call is shorter than the
178 required length for the pointer value plus a newline character,
179 subsequent reads from the same file descriptor will result in
180 completing the string, regardless of changes to the register by
183 descriptor needs to be opened to read the value again.
186 A write operation on the file results in setting the register to
187 the value given in the string. The string is parsed from the
188 beginning to the first non-numeric character or the end of the
189 buffer. Subsequent writes to the same file descriptor overwrite
190 the previous setting.
194 This file gives access to the Floating Point Status and Control Regis-
195 ter as a four byte long file. The operations on the fpcr file are:
200 the data buffer, containing the current value of the fpcr regis-
206 from the data buffer, updating the value of the fpcr register.
210 The two signal notification channels of an SPU. These are read-write
212 triggers an interrupt on the SPU. The value written to the signal
213 files can be read from the SPU through a channel read or from host user
214 space through the file. After the value has been read by the SPU, it
215 is reset to zero. The possible operations on an open signal1 or sig-
221 the data buffer, containing the current value of the specified
227 from the data buffer, updating the value of the specified signal
228 notification register. The signal notification register will
229 either be replaced with the input data or will be updated to the
230 bitwise OR of the old value and the input data, depending on the
231 contents of the signal1_type, or signal2_type respectively,
236 These two files change the behavior of the signal1 and signal2 notifi-
237 cation files. The contain a numerical ASCII string which is read as
238 either "1" or "0". In mode 0 (overwrite), the hardware replaces the
239 contents of the signal channel with the data that is written to it. in
240 mode 1 (logical OR), the hardware accumulates the bits that are subse-
241 quently written to it. The possible operations on an open signal1_type
245 When the count supplied to the read call is shorter than the
246 required length for the digit plus a newline character, subse-
247 quent reads from the same file descriptor will result in com-
248 pleting the string. When a complete string has been read, all
250 descriptor needs to be opened to read the value again.
253 A write operation on the file results in setting the register to
254 the value given in the string. The string is parsed from the
255 beginning to the first non-numeric character or the end of the
256 buffer. Subsequent writes to the same file descriptor overwrite
257 the previous setting.