Device Nodes

The datadev driver creates one character device and one /proc entry per detected PCIe card.

Quick Reference

Node	Permissions	Description
/dev/datadev_N	0666	Primary read/write interface. Open with O_RDWR.
/proc/datadev_N	read-only	Diagnostic state dump. Read with cat /proc/datadev_0.

/dev/ — Character Devices

The driver registers a character device for each hardware card using a dynamically allocated major:minor number. The device name is controlled by the cfgDevName module parameter.

Default naming (cfgDevName=0): sequential probe-order index.

/dev/datadev_0    # first card detected
/dev/datadev_1    # second card detected

PCI bus-number naming (cfgDevName nonzero): hex PCI bus number.

/dev/datadev_1a   # card on PCI bus 0x1a
/dev/datadev_1b   # card on PCI bus 0x1b

Use PCI bus-number naming when probe order is non-deterministic (e.g., in systems where PCIe slot enumeration order varies across reboots).

Permissions: 0666 — all users can open the device without sudo after the driver loads. This is set unconditionally in Dma_DevNode().

Maximum devices: up to 32 cards per system (MAX_DMA_DEVICES = 32).

Opening the device:

int fd = open("/dev/datadev_0", O_RDWR);
if (fd < 0) { perror("open"); return 1; }

/proc/ — Diagnostic Interface

Each device also creates a /proc/ entry with the same name as the /dev/ node:

/proc/datadev_0   # diagnostic dump for the first card

The /proc interface is read-only. It prints driver state including DMA buffer pool statistics, AXIS stream status, firmware version (from AxiVersion), and GPU state if GPU support is compiled in.

$ cat /proc/datadev_0
(driver state output — useful for verifying the driver loaded correctly
 and for diagnosing buffer exhaustion or DMA errors)

The /proc entry is removed when the driver is unloaded or the card is removed.

Multi-Device Systems

When multiple cards are present, each card gets its own /dev/ and /proc/ entry. Applications address a specific card by opening its device node:

int fd0 = open("/dev/datadev_0", O_RDWR);  /* first card  */
int fd1 = open("/dev/datadev_1", O_RDWR);  /* second card */

DMA buffer pools and channel masks are per-device — operations on fd0 do not affect fd1.