dmatest

Just some code to buid a kernel module to play around with the DMA bus. The actual intent is to create an RDMA demo eventually.

1. Direct Piping Interface:

   • Write to /dev/dma_in to send data
   • Read from /dev/dma_out to receive data

2. DMA Buffer Management:

   • Automatically allocates DMA buffers
   • Handles buffer size limitations

3. Progress Reporting:

   • Kernel logs show transfer progress
   • Percentage and byte counts reported

4. IOCTL Commands:

   • DMA_GET_PHYS_ADDR: Get physical DMA address
   • DMA_GET_BUFFER_SIZE: Get buffer size
   • DMA_TRANSFER_COMPLETE: Signal transfer completion

5. Synchronization:

   • Proper mutex protection for shared data
   • Wait queues for blocking operations

Usage example:

# Load the module
sudo insmod dma_pipe.ko

# Send data to DMA input
cat input_file > /dev/dma_in

# Receive data from DMA output
cat /dev/dma_out > output_file

# Monitor progress
dmesg | tail

3. **Verification Steps**:
```bash
# Check kernel version
uname -r

# Clean rebuild
make clean && make

# Load module
sudo insmod dma_transfer.ko

# Verify
dmesg | tail
ls -l /dev/dma_transfer

This solution:

• Maintains all DMA functionality
• Works across different kernel versions
• Includes proper error handling and cleanup
• Provides clear debug output

The module creates /dev/dma_transfer which can be used with standard file operations while utilizing DMA buffers for data transfer.

NOTE: You'll need a special NIC (InfiniBand or a RoCEv2-capable card to implement RDMA between hosts).