1SPUFS(2) Linux Programmer's Manual SPUFS(2)
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6 spufs - the SPU file system
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10 The SPU file system is used on PowerPC machines that implement the Cell
11 Broadband Engine Architecture in order to access Synergistic Processor
12 Units (SPUs).
13 The file system provides a name space similar to posix shared memory or
15 message queues. Users that have write permissions on the file system
16 can use spu_create(2) to establish SPU contexts in the spufs root.
17 Every SPU context is represented by a directory containing a predefined
19 set of files. These files can be used for manipulating the state of the
20 logical SPU. Users can change permissions on those files, but not actu‐
21 ally add or remove files.
22
25 uid=<uid>
26 set the user owning the mount point, the default is 0 (root).
27 gid=<gid>
29 set the group owning the mount point, the default is 0 (root).
30
33 The files in spufs mostly follow the standard behavior for regular sys‐
34 tem calls like read(2) or write(2), but often support only a subset of
35 the operations supported on regular file systems. This list details the
36 supported operations and the deviations from the behaviour in the
37 respective man pages.
38 All files that support the read(2) operation also support readv(2) and
40 all files that support the write(2) operation also support writev(2).
41 All files support the access(2) and stat(2) family of operations, but
42 only the st_mode, st_nlink, st_uid and st_gid fields of struct stat
43 contain reliable information.
44 All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2) opera‐
46 tions, but will not be able to grant permissions that contradict the
47 possible operations, e.g. read access on the wbox file.
48 The current set of files is:
50 /mem
53 the contents of the local storage memory of the SPU. This can be
54 accessed like a regular shared memory file and contains both code and
55 data in the address space of the SPU. The possible operations on an
56 open mem file are:
57 read(2), pread(2), write(2), pwrite(2), lseek(2)
59 These operate as documented, with the exception that seek(2),
60 write(2) and pwrite(2) are not supported beyond the end of the
61 file. The file size is the size of the local storage of the SPU,
62 which normally is 256 kilobytes.
63 mmap(2)
65 Mapping mem into the process address space gives access to the
66 SPU local storage within the process address space. Only
67 MAP_SHARED mappings are allowed.
68 /mbox
71 The first SPU to CPU communication mailbox. This file is read-only and
72 can be read in units of 32 bits. The file can only be used in non-
73 blocking mode and it even poll() will not block on it. The possible
74 operations on an open mbox file are:
75 read(2)
77 If a count smaller than four is requested, read returns -1 and
78 sets errno to EINVAL. If there is no data available in the mail
79 box, the return value is set to -1 and errno becomes EAGAIN.
80 When data has been read successfully, four bytes are placed in
81 the data buffer and the value four is returned.
82 /ibox
85 The second SPU to CPU communication mailbox. This file is similar to
86 the first mailbox file, but can be read in blocking I/O mode, and the
87 poll familiy of system calls can be used to wait for it. The possible
88 operations on an open ibox file are:
89 read(2)
91 If a count smaller than four is requested, read returns -1 and
92 sets errno to EINVAL. If there is no data available in the mail
93 box and the file descriptor has been opened with O_NONBLOCK, the
94 return value is set to -1 and errno becomes EAGAIN.
95 If there is no data available in the mail box and the file
97 descriptor has been opened without O_NONBLOCK, the call will
98 block until the SPU writes to its interrupt mailbox channel.
99 When data has been read successfully, four bytes are placed in
100 the data buffer and the value four is returned.
101 poll(2)
103 Poll on the ibox file returns (POLLIN | POLLRDNORM) whenever
104 data is available for reading.
105 /wbox
108 The CPU to SPU communation mailbox. It is write-only can can be written
109 in units of 32 bits. If the mailbox is full, write() will block and
110 poll can be used to wait for it becoming empty again. The possible
111 operations on an open wbox file are: write(2) If a count smaller than
112 four is requested, write returns -1 and sets errno to EINVAL. If there
113 is no space available in the mail box and the file descriptor has been
114 opened with O_NONBLOCK, the return value is set to -1 and errno becomes
115 EAGAIN.
116 If there is no space available in the mail box and the file descriptor
118 has been opened without O_NONBLOCK, the call will block until the SPU
119 reads from its PPE mailbox channel. When data has been read success‐
120 fully, four bytes are placed in the data buffer and the value four is
121 returned.
122 poll(2)
124 Poll on the ibox file returns (POLLOUT | POLLWRNORM) whenever
125 space is available for writing.
126 /mbox_stat
129 /ibox_stat
130 /wbox_stat
131 Read-only files that contain the length of the current queue, i.e. how
132 many words can be read from mbox or ibox or how many words can be writ‐
133 ten to wbox without blocking. The files can be read only in 4-byte
134 units and return a big-endian binary integer number. The possible
135 operations on an open *box_stat file are:
136 read(2)
138 If a count smaller than four is requested, read returns -1 and
139 sets errno to EINVAL. Otherwise, a four byte value is placed in
140 the data buffer, containing the number of elements that can be
141 read from (for mbox_stat and ibox_stat) or written to (for
142 wbox_stat) the respective mail box without blocking or resulting
143 in EAGAIN.
144 /npc
147 /decr
148 /decr_status
149 /spu_tag_mask
150 /event_mask
151 /srr0
152 Internal registers of the SPU. The representation is an ASCII string
153 with the numeric value of the next instruction to be executed. These
154 can be used in read/write mode for debugging, but normal operation of
155 programs should not rely on them because access to any of them except
156 npc requires an SPU context save and is therefore very inefficient.
157 The contents of these files are:
159 npc Next Program Counter
161 decr SPU Decrementer
163 decr_status Decrementer Status
165 spu_tag_mask MFC tag mask for SPU DMA
167 event_mask Event mask for SPU interrupts
169 srr0 Interrupt Return address register
171 The possible operations on an open npc, decr, decr_status,
173 spu_tag_mask, event_mask or srr0 file are:
174 read(2)
176 When the count supplied to the read call is shorter than the
177 required length for the pointer value plus a newline character,
178 subsequent reads from the same file descriptor will result in
179 completing the string, regardless of changes to the register by
180 a running SPU task. When a complete string has been read, all
181 subsequent read operations will return zero bytes and a new file
182 descriptor needs to be opened to read the value again.
183 write(2)
185 A write operation on the file results in setting the register to
186 the value given in the string. The string is parsed from the
187 beginning to the first non-numeric character or the end of the
188 buffer. Subsequent writes to the same file descriptor overwrite
189 the previous setting.
190 /fpcr
193 This file gives access to the Floating Point Status and Control Regis‐
194 ter as a four byte long file. The operations on the fpcr file are:
195 read(2)
197 If a count smaller than four is requested, read returns -1 and
198 sets errno to EINVAL. Otherwise, a four byte value is placed in
199 the data buffer, containing the current value of the fpcr regis‐
200 ter.
201 write(2)
203 If a count smaller than four is requested, write returns -1 and
204 sets errno to EINVAL. Otherwise, a four byte value is copied
205 from the data buffer, updating the value of the fpcr register.
206 /signal1
209 /signal2
210 The two signal notification channels of an SPU. These are read-write
211 files that operate on a 32 bit word. Writing to one of these files
212 triggers an interrupt on the SPU. The value writting 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‐
216 nal2 file are:
217 read(2)
219 If a count smaller than four is requested, read returns -1 and
220 sets errno to EINVAL. Otherwise, a four byte value is placed in
221 the data buffer, containing the current value of the specified
222 signal notification register.
223 write(2)
225 If a count smaller than four is requested, write returns -1 and
226 sets errno to EINVAL. Otherwise, a four byte value is copied
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 or the old value and the input data, depending on the
231 contents of the signal1_type, or signal2_type respectively,
232 file.
233 /signal1_type
236 /signal2_type
237 These two files change the behavior of the signal1 and signal2 notifi‐
238 cation files. The contain a numerical ASCII string which is read as
239 either "1" or "0". In mode 0 (overwrite), the hardware replaces the
240 contents of the signal channel with the data that is written to it. in
241 mode 1 (logical OR), the hardware accumulates the bits that are subse‐
242 quently written to it. The possible operations on an open signal1_type
243 or signal2_type file are:
244 read(2)
246 When the count supplied to the read call is shorter than the
247 required length for the digit plus a newline character, subse‐
248 quent reads from the same file descriptor will result in com‐
249 pleting the string. When a complete string has been read, all
250 subsequent read operations will return zero bytes and a new file
251 descriptor needs to be opened to read the value again.
252 write(2)
254 A write operation on the file results in setting the register to
255 the value given in the string. The string is parsed from the
256 beginning to the first non-numeric character or the end of the
257 buffer. Subsequent writes to the same file descriptor overwrite
258 the previous setting.
259
262 /etc/fstab entry
263 none /spu spufs gid=spu 0 0
264
267 Arnd Bergmann <arndb@de.ibm.com>, Mark Nutter <mnutter@us.ibm.com>,
268 Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
269
271 capabilities(7), close(2), spu_create(2), spu_run(2), spufs(7)
272Linux 2005-09-28 SPUFS(2)