HostToDevice

Host-to-device refers to data transfers in which the host system initiates movement of data to a peripheral device or accelerator. It contrasts with device-to-host transfers and is a common concept across interfaces such as USB, PCI Express, and GPU programming. The term is used in APIs and drivers to designate the direction of a transfer and the source and destination memory.

USB examples: host-to-device transfers are initiated by the host toward the device, including control, bulk, interrupt, and isochronous transfers. The host schedules these transfers, while the device responds and reports status.

In GPU and HPC contexts, host-to-device often means copying memory from host RAM to device memory so the device can perform computation. APIs such as CUDA's cudaMemcpyHostToDevice or OpenCL's clEnqueueCopyBuffer illustrate this direction; transfers may be synchronous or asynchronous.

Mechanisms commonly use DMA to move data with minimal CPU involvement, with memory mappings (BARs) and IOMMU protections used to ensure correctness and isolation.

Performance considerations include bandwidth, latency, alignment, and overlapping transfers with computation via asynchronous operations. Security concerns involve access control and isolation to prevent unauthorized writes.

See also: device-to-host transfer, DMA, PCI Express, USB, CUDA memory management, OpenCL memory management.