driver.storage.iorequest

I/O request allocation and lifecycle helpers.

Overview

This unit provides heap allocation, copying, and freeing of TIORequest records used by the submit_io / complete_io path in driver.storage.mgr. It separates the memory management concern from the dispatch logic.

The key operation is ioreq_copy, which creates a heap-allocated copy of a CFIFO value-element. This copy is required for ISR safety: once a request is dequeued from the CFIFO and dispatched to hardware, the driver completion callback may fire on any stack at any time, so the request must reside on the heap rather than on a caller's stack.

Dependencies

• memory.heap
• driver.storage.types

Functions and Procedures

ioreq_alloc

function ioreq_alloc(reqType  : TIORequestType;
                     device   : PStorage_Device;
                     lba      : uint32;
                     sectors  : uint32;
                     buf      : pointer) : PIORequest;

Allocates a new TIORequest on the heap and initialises its core fields. ByteCount, Error, Caller, UserData, Callback, and CallbackData are zeroed. The state is set to iosPending. Returns nil on allocation failure.

ioreq_free

procedure ioreq_free(req : PIORequest);

Frees a heap-allocated TIORequest. Safe to call with nil.

ioreq_copy

function ioreq_copy(src : PIORequest) : PIORequest;

Performs a shallow copy of src into a new heap allocation. All fields are duplicated by value; the Buffer pointer is copied but the buffer itself is not duplicated. Returns nil on allocation failure.

Notes

• ioreq_alloc is provided as a convenience for drivers that construct requests programmatically. The storage manager's public API (storage_read, storage_write) builds stack-local requests instead and copies them via ioreq_copy in dispatch_next.
• The copy performed by ioreq_copy is intentionally shallow: the data buffer pointed to by Buffer is shared between the original and the copy. Only the TIORequest record itself is duplicated.