Kernel-Module

Kernel module for FPGA-Linux communication via DMA and AXI registers.

This kernel module is responsible for facilitating data exchange between an FPGA (THANNA-IP-CORE) and the Linux operating system. It initializes a DMA region that allows efficient data transfer between the two entities and provides an API to interact with the AXI slave registers through IOCTL system calls. The module also registers a character device at /dev/thanna, which supports various operations including read, write, seek, and mmap. These operations can be accessed using the provided libthanna library or directly through user space applications.

Key features:

  • DMA Region Initialization: Sets up a shared memory space between the FPGA and the Linux kernel for efficient data transfers.

  • AXI Register Access via IOCTL: Allows reading, writing, and updating of AXI slave registers using IOCTL calls (READ_REG, WRITE_REG, UPDATE_REG_BITS).

  • Character Device Interface: Registers a device at /dev/thanna that provides standard character device operations (read, write, seek, mmap) to interact with the FPGA.

Defines

dbg_info(dev, fmt, args...)

Prints debug information to the kernel log.

Parameters:

  • dev – The device structure.

  • fmt – Format string.

  • args – Variable arguments for the format string.

dbg_err(dev, fmt, args...)

Prints an error message to the kernel log.

Parameters:

  • dev – The device structure.

  • fmt – Format string.

  • args – Variable arguments for the format string.

dbg_warn(dev, fmt, args...)

Prints a warning message to the kernel log.

Parameters:

  • dev – The device structure.

  • fmt – Format string.

  • args – Variable arguments for the format string.

DRIVER_NAME

Name of the driver for the Thanna device.

THANNA_IP_CORE_S00_AXI_SLV_REG0_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG1_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG2_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG3_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG4_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG5_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG6_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG7_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IP_CORE_S00_AXI_SLV_REG8_OFFSET

Offset definition for the Thanna IP core AXI slave register.

THANNA_IOCTL_READ_REG

IOCTL command to read from a register.

Parameters:

  • 'q' – The magic number.

  • 1 – The command number.

  • u32 – The type of the data passed to the command.

THANNA_IOCTL_WRITE_REG

IOCTL command to write to a register.

Parameters:

  • 'q' – The magic number.

  • 2 – The command number.

  • u32 – The type of the data passed to the command.

THANNA_IOCTL_UPDATE_REG_BITS

IOCTL command to update specific bits in a register.

Parameters:

  • 'q' – The magic number.

  • 3 – The command number.

  • u32 – The type of the data passed to the command.

THANNA_IOCTL_FLUSH_CACHE

IOCTL command to flush the cache.

Parameters:

  • 'q' – The magic number.

  • 4 – The command number.

Functions

static ssize_t thanna_read(struct file *file, char __user *user_buffer, size_t len, loff_t *offs)

Reads data from the device.

This function is called when a user reads from the device file.

Parameters:

  • file – Pointer to the file structure.

  • user_buffer – Pointer to the user-space buffer.

  • len – Length of data to read.

  • offs – Offset in the device file.

Returns:

Number of bytes read on success, or negative error code on failure.

static ssize_t thanna_write(struct file *file, const char __user *user_buffer, size_t len, loff_t *offs)

Writes data to the device.

This function is called when a user writes to the device file.

Parameters:

  • file – Pointer to the file structure.

  • user_buffer – Pointer to the user-space buffer.

  • len – Length of data to write.

  • offs – Offset in the device file.

Returns:

Number of bytes written on success, or negative error code on failure.

static loff_t thanna_llseek(struct file *file, loff_t offset, int whence)

Changes the current file position.

This function is called when a user changes the file offset.

Parameters:

  • file – Pointer to the file structure.

  • offset – New file offset.

  • whence – Seek mode.

Returns:

New file offset on success, or negative error code on failure.

static int thanna_mmap(struct file *file, struct vm_area_struct *vma)

Memory-maps the device memory to user space.

This function is called when a user performs an mmap operation on the device file.

Parameters:

  • file – Pointer to the file structure.

  • vma – Pointer to the virtual memory area structure.

Returns:

0 on success, or negative error code on failure.

static long thanna_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

Handles IOCTL commands for the device.

This function is called when a user performs an ioctl operation on the device file.

Parameters:

  • file – Pointer to the file structure.

  • cmd – IOCTL command.

  • arg – Command argument.

Returns:

0 on success, or negative error code on failure.

struct thanna_local
#include <thanna.h>

Local data structure to store Thanna device state.

This structure stores the state of the Thanna device, including memory regions, DMA addresses, and IRQ.

Public Members

int irq

IRQ number for the device

unsigned long mem_start

Start address of the device memory region

unsigned long mem_end

End address of the device memory region

dma_addr_t dma_start

Start address of the DMA region

dma_addr_t dma_end

End address of the DMA region

void *v_dma_start

Virtual start address of the DMA region

void __iomem *base_addr

Base address of the memory-mapped I/O