filesystems/spufs/spufs.rst

1 .. SPDX-License-Identifier: GPL-2.0
10        spufs - the SPU file system
21        message queues. Users that have write permissions on  the  file  system
26        logical SPU. Users can change permissions on those files, but not actu-
43        The files in spufs mostly follow the standard behavior for regular sys-
44        tem  calls like read(2) or write(2), but often support only a subset of
50        all  files  that support the write(2) operation also support writev(2).
55        All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2)  opera-
65        data in the address space of the SPU.  The possible  operations  on  an
68        read(2), pread(2), write(2), pwrite(2), lseek(2)
70               write(2) and pwrite(2) are not supported beyond the end  of  the
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-
87               If  a  count smaller than four is requested, read returns -1 and
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.
90               When data has been read successfully, four bytes are  placed  in
91               the data buffer and the value four is returned.
101               If a count smaller than four is requested, read returns  -1  and
102               sets errno to EINVAL.  If there is no data available in the mail
104               return value is set to -1 and errno becomes EAGAIN.
106               If  there  is  no  data  available  in the mail box and the file
109               When data has been read successfully, four bytes are  placed  in
110               the data buffer and the value four is returned.
114               data is available for reading.
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
121        operations  on  an open wbox file are: write(2) If a count smaller than
122        four is requested, write returns -1 and sets errno to EINVAL.  If there
124        opened with O_NONBLOCK, the return value is set to -1 and errno becomes
129        reads  from  its PPE mailbox channel.  When data has been read success-
130        fully, four bytes are placed in the data buffer and the value  four  is
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
146               If a count smaller than four is requested, read returns  -1  and
148               the data buffer, containing the number of elements that  can  be
157        can  be  used in read/write mode for debugging, but normal operation of
185        write(2)
186               A write operation on the file results in setting the register to
188               beginning to the first non-numeric character or the end  of  the
194        This file gives access to the Floating Point Status and Control  Regis-
198               If  a  count smaller than four is requested, read returns -1 and
200               the data buffer, containing the current value of the fpcr regis-
203        write(2)
204               If a count smaller than four is requested, write returns -1  and
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
215        is  reset  to zero.  The possible operations on an open signal1 or sig-
219               If a count smaller than four is requested, read returns  -1  and
221               the data buffer, containing the current value of  the  specified
224        write(2)
225               If  a count smaller than four is requested, write returns -1 and
227               from the data buffer, updating the value of the specified signal
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
236        These two files change the behavior of the signal1 and signal2  notifi-
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-
246               required  length  for the digit plus a newline character, subse-
247               quent reads from the same file descriptor will  result  in  com-
252        write(2)
253               A write operation on the file results in setting the register to
255               beginning  to  the first non-numeric character or the end of the