What information is displayed by the command cat/proc/dma?

The /proc/dma virtual file is maintained by the Linux kernel and updated dynamically as device drivers register or release ISA DMA channels. Each line pairs a channel number with the driver that has claimed it, directly indicating whether DMA is enabled and active on the running system. This file is the standard kernel-provided mechanism for querying DMA channel enablement status.

The file records channel-to-driver registration mappings; the registration entry itself is what indicates enablement, so listing 'channels in use' is a consequence of DMA being enabled rather than the primary information displayed.

/proc/dma does not report DMA transfer modes such as burst, demand, or cycle-steal; it only records which channels are claimed by which drivers.

/proc/dma contains only per-channel registration entries, not a broad general overview or summary of DMA hardware capabilities on the machine.