sched

This context may be scheduled.

step

This context can be run in single-step mode, for debugging.

New capabilities flags may be added in the future.

read(2), pread(2), write(2), pwrite(2), lseek(2)

These operate as usual, with the exception that lseek(2), write(2), and 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.

mmap(2)

Mapping mem into the process address space provides access to the SPU local storage within the process address space. Only MAP_SHARED mappings are allowed.

read(2)

If count is smaller than four, read(2) returns −1 and sets errno to EINVAL. If there is no data available in the mailbox (i.e., the SPU has not sent a mailbox message), the return value is set to −1 and errno is set to EAGAIN. When data has been read successfully, four bytes are placed in the data buffer and the value four is returned.

read(2)

If count is smaller than four, read(2) returns −1 and sets errno to EINVAL. If there is no data available in the mailbox and the file descriptor has been opened with O_NONBLOCK, the return value is set to −1 and errno is set to EAGAIN.

If there is no data available in the mailbox and the file descriptor has been opened without 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.

poll(2)

Poll on the ibox file returns (POLLIN | POLLRDNORM) whenever data is available for reading.

write(2)

If count is smaller than four, write(2) returns −1 and sets errno to EINVAL. If there is no space available in the mailbox and the file descriptor has been opened with O_NONBLOCK, the return value is set to −1 and errno is set to EAGAIN.

If there is no space available in the mailbox and the file descriptor has been opened without O_NONBLOCK, the call will block until the SPU reads from its PPE (PowerPC Processing Element) mailbox channel. When data has been written successfully, the system call returns four as its function result.

poll(2)

A poll on the wbox file returns (POLLOUT | POLLWRNORM) whenever space is available for writing.

read(2)

If count is smaller than four, read(2) returns −1 and sets errno to 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 mbox_stat and ibox_stat) or written to (for wbox_stat) the respective mailbox without blocking or returning an EAGAIN error.

npc

Next Program Counter − only valid when the SPU is in a stopped state.

decr

SPU Decrementer

decr_status

Decrementer Status

spu_tag_mask

MFC tag mask for SPU DMA

event_mask

Event mask for SPU interrupts

event_status

Number of SPU events pending (read-only)

srr0

Interrupt Return address register

lslr

Local Store Limit Register

read(2)

Reads the current register value. If the register value is larger than the buffer passed to the read(2) system call, subsequent reads will continue reading from the same buffer, until the end of the buffer is reached.

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.

write(2)

A 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.

Except for the npc file, these files are not present on contexts that have been created with the SPU_CREATE_NOSCHED flag.

read(2)

If count is smaller than four, read(2) returns −1 and sets errno to EINVAL. Otherwise, a four-byte value is placed in the data buffer; this is the current value of the fpcr register.

write(2)

If count is smaller than four, write(2) returns −1 and sets errno to EINVAL. Otherwise, a four-byte value is copied from the data buffer, updating the value of the fpcr register.

read(2)

If count is smaller than four, read(2) returns −1 and sets errno to EINVAL. Otherwise, a four-byte value is placed in the data buffer; this is the current value of the specified signal notification register.

write(2)

If count is smaller than four, write(2) returns −1 and sets errno to 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 signal1_type or signal2_type files respectively.

read(2)

When the count supplied to the 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.

write(2)

A 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.

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];
};

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;
};

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];
};

read(2)

Reads from the cntl file will return an ASCII string with the hex value of the SPU Status register.

write(2)

Writes to the cntl file will set the context's SPU Run Control register.

write(2)

Writes to this file need to be in the format of a MFC DMA command, defined as follows:

struct	mfc_dma_command {
	int32_t		pad;	/* reserved */
	uint32_t		lsa;	/* local storage address */
	uint64_t		ea;	/* effective address */
	uint16_t		size;	/* transfer size */
	uint16_t		tag;	/* command tag */
	uint16_t		class;	/* class ID */
	uint16_t		cmd;	/* command opcode */
};

Writes are required to be exactly sizeof(struct mfc_dma_command) bytes in size. The command will be sent to the SPU's MFC proxy queue, and the tag stored in the kernel (see below).

read(2)

Reads the contents of the tag status register. If the file is opened in blocking mode (i.e., without O_NONBLOCK), then the read will block until a DMA tag (as performed by a previous write) is complete. In non-blocking mode, the MFC tag status register will be returned without waiting.

poll(2)

Calling poll(2) on the mfc file will block until a new DMA can be started (by checking for POLLOUT) or until a previously started DMA (by checking for POLLIN) has been completed.

/mss Provides access to the MFC MultiSource Synchronization (MSS) facility. By mmap(2)-ing this file, processes can access the MSS area of the SPU.

The following operations are supported:

mmap(2)

Mapping mss into the process address space gives access to the SPU MSS area within the process address space. Only MAP_SHARED mappings are allowed.

mmap(2)

Mapping psmap gives a process a direct map of the SPU problem state area. Only MAP_SHARED mappings are supported.

write(2)

By writing an ASCII hex value into this file, applications can set the object ID of the SPU context. Any previous value of the object ID is overwritten.

read(2)

Reading this file gives an ASCII hex string representing the object ID for this SPU context.