Mount options¶

uid=<uid>

Set the user owning the mount point; the default is 0 (root).

gid=<gid>

Set the group owning the mount point; the default is 0 (root).

mode=<mode>

Set the mode of the top-level directory in spufs, as an octal mode string. The default is 0775.

Files¶

All files that support the read(2) operation also support readv(2) and all files that support the write(2) operation also support writev(2). All files support the access(2) and stat(2) family of operations, but for the latter call, the only fields of the returned stat structure that contain reliable information are st_mode, st_nlink, st_uid, and st_gid.

All files support the chmod(2)/fchmod(2) and chown(2)/fchown(2) operations, but will not be able to grant permissions that contradict the possible operations (e.g., read access on the wbox file).

The current set of files is:

/capabilities

Contains a comma-delimited string representing the capabilities of this SPU context. Possible capabilities are:

/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 mem file are:

/regs

Contains the saved general-purpose registers of the SPU context. This file contains the 128-bit values of each register, from register 0 to register 127, in order. This allows the general-purpose registers to be inspected for debugging.

Reading to or writing from this file requires that the context is scheduled out, so use of this file is not recommended in normal program operation.

The regs file is not present on contexts that have been created with the SPU_CREATE_NOSCHED flag.

/mbox

The first SPU-to-CPU communication mailbox. This file is read-only and can be read in units of 4 bytes. The file can be used only in nonblocking mode - even poll(2) cannot be used to block on this file. The only possible operation on an open mbox file is:

/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 calling read(2) on an open ibox file will block until the SPU has written data to its interrupt mailbox channel (unless the file has been opened with O_NONBLOCK, see below). Also, poll(2) and similar system calls can be used to monitor for the presence of mailbox data.

The possible operations on an open ibox file are:

/wbox

The CPU-to-SPU communication mailbox. It is write-only and can be written in units of four bytes. If the mailbox is full, write(2) will block, and poll(2) can be used to block until the mailbox is available for writing again. The possible operations on an open wbox file are:

/mbox_stat, /ibox_stat, /wbox_stat

These are read-only files that contain the length of the current queue of each mailbox—that is, how many words can be read from mbox or ibox or how many words can be written to wbox without blocking. The files can be read only in four-byte units and return a big-endian binary integer number. The only possible operation on an open *box_stat file is:

/npc, /decr, /decr_status, /spu_tag_mask, /event_mask, /event_status, /srr0, /lslr

Internal registers of the SPU. These files contain an ASCII string representing the hex value of the specified register. Reads and writes on these files (except for npc, see below) require that the SPU context be scheduled out, so frequent access to these files is not recommended for normal program operation.

The contents of these files are:

The possible operations on these files are:

/fpcr

This file provides access to the Floating Point Status and Control Register (fcpr) as a binary, four-byte file. The operations on the fpcr file are:

/signal1, /signal2

The files provide access to the two signal notification channels of an SPU. These are read-write files that operate on four-byte 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 signal1 or signal2 file are:

/signal1_type, /signal2_type

These two files change the behavior of the signal1 and signal2 notification files. They contain a numeric 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 signal1_type or signal2_type file are:

/mbox_info, /ibox_info, /wbox_info, /dma_into, /proxydma_info

Read-only files that contain the saved state of the SPU mailboxes and DMA queues. This allows the SPU status to be inspected, mainly for debugging. The mbox_info and ibox_info files each contain the four-byte mailbox message that has been written by the SPU. If no message has been written to these mailboxes, then contents of these files is undefined. The mbox_stat, ibox_stat and wbox_stat files contain the available message count.

The wbox_info file contains an array of four-byte mailbox messages, which have been sent to the SPU. With current CBEA machines, the array is four items in length, so up to 4 * 4 = 16 bytes can be read from this file. If any mailbox queue entry is empty, then the bytes read at the corresponding location are undefined.

The dma_info file contains the contents of the SPU MFC DMA queue, represented as the following structure:

struct spu_dma_info {
    uint64_t         dma_info_type;
    uint64_t         dma_info_mask;
    uint64_t         dma_info_status;
    uint64_t         dma_info_stall_and_notify;
    uint64_t         dma_info_atomic_command_status;
    struct mfc_cq_sr dma_info_command_data[16];
};

    

The last member of this data structure is the actual DMA queue, containing 16 entries. The mfc_cq_sr structure is defined as:

struct mfc_cq_sr {
    uint64_t mfc_cq_data0_RW;
    uint64_t mfc_cq_data1_RW;
    uint64_t mfc_cq_data2_RW;
    uint64_t mfc_cq_data3_RW;
};

    

The proxydma_info file contains similar information, but describes the proxy DMA queue (i.e., DMAs initiated by entities outside the SPU) instead. The file is in the following format:

struct spu_proxydma_info {
    uint64_t         proxydma_info_type;
    uint64_t         proxydma_info_mask;
    uint64_t         proxydma_info_status;
    struct mfc_cq_sr proxydma_info_command_data[8];
};

    

Accessing these files requires that the SPU context is scheduled out - frequent use can be inefficient. These files should not be used for normal program operation.

These files are not present on contexts that have been created with the SPU_CREATE_NOSCHED flag.

/cntl

This file provides access to the SPU Run Control and SPU status registers, as an ASCII string. The following operations are supported:

/mfc

Provides access to the Memory Flow Controller of the SPU. Reading from the file returns the contents of the SPU's MFC Tag Status register, and writing to the file initiates a DMA from the MFC. The following operations are supported:

/psmap

Provides access to the whole problem-state mapping of the SPU. Applications can use this area to interface to the SPU, rather than writing to individual register files in spufs.

The following operations are supported:

/phys-id

Read-only file containing the physical SPU number that the SPU context is running on. When the context is not running, this file contains the string "-1".

The physical SPU number is given by an ASCII hex string.

/object-id

Allows applications to store (or retrieve) a single 64-bit ID into the context. This ID is later used by profiling tools to uniquely identify the context.