Queue depth management for communication between host and peripheral device

A method for managing a wrap-around information transfer queue in a memory of a host subsystem, for use with a peripheral device that can write into the information transfer queue via a communication channel, comprising steps of:

• the peripheral device writing new entries into the information transfer queue at locations in the memory identified by a device centric write pointer accessible by the device, and in conjunction therewith, updating the device centric write pointer;
• the host subsystem checking a cleared status of an entry in the information transfer queue just prior to a particular location in the memory identified by a host centric read pointer accessible by the host;
• the host subsystem, if the entry just prior to the particular location is found to be cleared in the step of checking a cleared status of an entry, consuming the entry identified by a host centric read pointer and in conjunction therewith, clearing the entry identified by a host centric read pointer and updating the host centric read pointer;
• and the host subsystem, if the entry just prior to the particular location is found to be not cleared in the step of checking a cleared status of an entry, signaling a buffer overflow condition.

A method for managing an information transfer queue in a memory of a host subsystem, for use with a peripheral device that can write into the information transfer queue via a communication channel, comprising steps of:

• the peripheral device writing new entries into the information transfer queue at locations in the memory indicated by a device centric write pointer, accessible by the device, and in conjunction therewith, updating the device centric write pointer;
• and
• the host subsystem consuming entries from the information transfer queue at locations in the memory indicated by a host centric read pointer, accessible by the host, and in conjunction therewith, updating the host centric read pointer,
• wherein the host centric read pointer is accessible to the host subsystem for reading and updating without using the communication channel,
• wherein the device centric write pointer for the information transfer queue is accessible to the peripheral device for reading and updating without using the communication channel,
• and wherein the host subsystem does not maintain a write pointer for the information transfer queue.

A method for managing an information transfer queue in a memory of a host subsystem, for use by a peripheral device that can write into the information transfer queue via a communication channel, wherein the host subsystem includes a host centric read pointer accessible by the host subsystem for the information transfer queue, and the peripheral device includes a device centric write pointer accessible by the peripheral device for the information transfer queue, for use further with a second queue accessible to both the host subsystem and the peripheral device, the second queue having a number of entries present, comprising steps of:

• the peripheral device determining a particular number, in dependence upon a device centric indication of the number of entries present in the second queue, the particular number being a number of new entries of a particular type that the peripheral device has been authorized to write into the information transfer queue;
• and
• the peripheral device writing new entries of the particular type into locations identified by the device centric write pointer in the information transfer queue in dependence upon the particular number and in conjunction therewith, updating the device centric write pointer,
• wherein the host subsystem does not maintain a write pointer for the information transfer queue.