Data chaining mechanism for SCSI devices

A computer system comprising a bus, a processor coupled to said bus;

• a memory means coupled to said bus for storing data;
• a plurality of Small Computer Standard Interface (SCSI) devices coupled to said bus, wherein a SCSI manager provides routines and data structures for controlling communication between said plurality of SCSI devices, said computer system further comprising a mechanism for exchanging information between said SCSI devices including:
• first means coupled to said bus for moving data between said SCSI devices, said means for moving including means for generating at least one move operation, wherein said means for generating has at least a first opcode field, a first count field, and a first offset field, wherein said first opcode field contains a move command represented as a buffer address, said count field specifies a number of bytes to transfer, and said first offset field contains an offset value to add to said buffer address;
• and
• second means coupled to said bus for repeating an operation, wherein said means for repeating includes means for generating at least one looping operation, said means for generating at least one looping operation having at least a second opcode field, a second count field, and a second offset field, wherein said second opcode field specifies the looping operation, said second count field contains a loop count, said second offset field contains an offset number of operations for repeating in said at least one looping operation;
• wherein said at least one move operation and said at least one looping operation are ordered for sequential execution by said SCSI manager, and further wherein said SCSI manager transfers said number of bytes to or from said buffer address and subsequently adds said offset value to said buffer address to create a current buffer address in one atomic operation upon execution of said at least one move operation and said SCSI manager repeats operations within said offset number of said looping operation in said sequential order until said loop count is exhausted upon execution of said at least one looping operation, wherein said at least one move operation accommodates a plurality of buffer addresses;
• said SCSI manager transferring said number of bytes to or from said current buffer address when said SCSI manager re-executes said at least one move operation, wherein transfers occur between SCSI devices by allowing said at least one move operation to specify multiple source or destination buffers.

A computer system comprising a bus, a processor coupled to said bus;

• a memory means coupled to said bus for storing data;
• a plurality of Small Computer Standard Interface (SCSI) devices coupled to said bus, wherein a SCSI manager provides routines and data structures for controlling communication between said plurality of SCSI devices;
• a mechanism for exchanging information between said SCSI devices including:
• first means coupled to said SCSI manager for moving data between SCSI devices, said means for moving including means for generating at least one move operation, wherein said means for generating has at least a first opcode field, a first count field, and a first offset field, wherein said first opcode field contains a move command represented as a buffer address, said count field specifies a number of bytes to transfer, and said first offset field contains an offset value to add to said buffer address, wherein said SCSI manager transfers said number of bytes to or from said buffer address and subsequently adds said offset value to said buffer address to create a current buffer address in one atomic operation upon execution of said at least one move operation, wherein said move command accommodates a plurality of buffer addresses;
• and
• second means coupled to said SCSI manager for repeating said at least one move operation, wherein said SCSI manager transfers said number of bytes to or from said current buffer address when said SCSI manager re-executes said at least one move operation, wherein information is exchanged between SCSI devices by having each move operation specify multiple source or destination buffers.

In a computer system having a bus and utilizing a Small Computer Standard Interface (SCSI), wherein a SCSI manager provides routines and data structures for controlling communication between a plurality of SCSI devices, a method for exchanging information between said SCSI devices said method comprising the steps of:

• moving data between said SCSI devices, said step of moving including the step of generating at least one move operation comprising a first opcode field, a first count field, and a first offset field, wherein said first opcode field contains a move command represented as a buffer address, said count field specifies a number of bytes to transfer, and said first offset field contains an offset value to add to said buffer address, wherein at least one move operation accommodates a plurality of buffer addresses;
• repeating an operation, wherein the step of repeating includes the step of generating at least one looping operation comprising a second opcode field, a second count field, and a second offset field, wherein said second opcode field specifies the looping operation, said second count field contains a loop count, and said second offset field contains an offset number of operations for repeating in said at least one looping operation;
• executing each of said at least one move operation wherein said SCSI manager either transfers said number of bytes to or from said buffer address and subsequently adds said offset value to said buffer address to create a current buffer address in one atomic operation;
• and
• executing said looping operation wherein said SCSI manager repeats operations within said offset number of each said looping operation, wherein said SCSI manager repeats said at least one move instruction until said loop count is exhausted wherein said SCSI manager transfers said number of bytes to or from said current buffer address, wherein transfers occur between SCSI devices by allowing said at least one move operation to specify multiple source or destination buffers.

In a computer system having a bus and utilizing a Small Computer Standard Interface (SCSI), wherein a SCSI manager provides routines and data structures for controlling communication between a plurality of SCSI devices, a method for exchanging information between said SCSI devices, said method comprising the steps of:

• moving data between said SCSI devices, said step of moving including the step of generating at least one move operation comprising a first opcode field, a first count field, and a first offset field, wherein said first opcode field contains a move command represented as a buffer address, said count field specifies a number of bytes to transfer, and said first offset field contains an offset value to add to said buffer address, wherein said at least one move operation accommodates a plurality of buffer addresses;
• repeating an operation, wherein the step of repeating includes the step of generating at least one looping operation comprising a second opcode field, a second count field, and a second offset field, wherein said second opcode field specifies the looping operation, said second count field contains a loop count, and said second offset field contains an offset number of operations for repeating in said at least one looping operation;
• generating a stop operation comprising a third opcode field, a third count field, and a third offset field, wherein said third opcode field specifies the stop operation;
• executing each of said at least one move operation such that said SCSI manager either transfers said number of bytes to or from said buffer address and subsequently adds said offset value to said buffer address to create a current buffer address in one atomic operation;
• and
• executing said looping operation wherein said SCSI manager repeats operations within said offset number of each said looping operation, such that said SCSI manager repeats said at least one move instruction until said loop count is exhausted wherein said SCSI manager transfers said number of bytes to or from said current buffer address, wherein transfers occur between SCSI devices by allowing said at least one move operation to specify multiple source or destination buffers;
• and
• executing said stop operation such that said SCSI manager completes execution of said operations.