Function rt_dma_chan_request

components/drivers/dma/dma.c:486–564

}

struct rt_dma_chan *rt_dma_chan_request(struct rt_device *dev, const char *name)
{
    void *fw_data = RT_NULL;
    struct rt_dma_chan *chan;
    struct rt_ofw_cell_args dma_args;
    struct rt_dma_controller *ctrl = RT_NULL;

    if (!dev)
    {
        return rt_err_ptr(-RT_EINVAL);
    }

    if (name)
    {
        fw_data = &dma_args;
        ctrl = ofw_find_dma_controller(dev, name, &dma_args);
    }
    else
    {
        struct rt_dma_controller *ctrl_tmp;

        rt_spin_lock(&dmac_nodes_lock);
        rt_list_for_each_entry(ctrl_tmp, &dmac_nodes, list)
        {
            /* Only memory to memory for uname request */
            if (rt_bitmap_test_bit(ctrl_tmp->dir_cap, RT_DMA_MEM_TO_MEM))
            {
                ctrl = ctrl_tmp;
                break;
            }
        }
        rt_spin_unlock(&dmac_nodes_lock);
    }

    if (rt_is_err_or_null(ctrl))
    {
        return ctrl ? ctrl : rt_err_ptr(-RT_ENOSYS);
    }

    if (ctrl->ops->request_chan)
    {
        chan = ctrl->ops->request_chan(ctrl, dev, fw_data);
    }
    else
    {
        chan = rt_calloc(1, sizeof(*chan));

        if (!chan)
        {
            chan = rt_err_ptr(-RT_ENOMEM);
        }
    }

    if (rt_is_err(chan))
    {
        return chan;
    }