ibvopendevice

ibv_open_device is a function in the libibverbs library that opens an InfiniBand or RDMA device by obtaining a device context. It takes a pointer to a device object and returns a pointer to a context on success, or NULL on error.

Prototype: struct ibv_context *ibv_open_device(struct ibv_device *device);

Usage typically follows discovery of devices. Applications first obtain a list of devices with ibv_get_device_list, select a device from the list, and then call ibv_open_device(device) to acquire a context. The returned context can be used for further RDMA operations, such as creating protection domains, queue pairs, and memory regions. When finished, the context is released with ibv_close_device(ctx), and the device list is freed with ibv_free_device_list.

Error handling: If the operation fails, ibv_open_device returns NULL and errno is set to indicate the error. Common error indications include invalid input (EINVAL), no such device (ENODEV), or insufficient permissions (EACCES). The exact cause depends on the hardware, driver, and how the process is permitted to access the device.

Relation to other API elements: ibv_open_device is part of the broader libibverbs API used for user-space interaction with RDMA-capable devices. It is typically followed by resource allocation calls such as ibv_alloc_pd and other verbs operations through the obtained ibv_context. Proper usage requires a compatible kernel driver and device.

Notes: The function is intended for applications that directly manage RDMA resources. Developers should ensure proper cleanup and error handling to avoid resource leaks and to handle environments with multiple devices or restricted permissions.