Overview

All the basic functionality can be found in the file flink_core.c together with all necessary types and prototypes in flink.h. Bus Communication Modules implement this basic functionality for a given hardware interface.

Data Structures

The information for a specific flink device will be stored in a structure flink_device.

// ############ flink device ############
struct flink_device {
    struct list_head      list;
    u8                    id;
    u8                    nof_subdevices;
    struct list_head      subdevices;
    struct flink_bus_ops* bus_ops;
    struct module*        appropriated_module;
    void*                 bus_data;
    struct cdev*          char_device;
    struct device*        sysfs_device;
};

All flink devices which are present in a system will be inserted in a linked list.

A flink device will contain one or several subdevices. Those subdevices are represented by the structure flink_subdevice.

// ############ flink subdevice ############
struct flink_subdevice {
    struct list_head     list;
    struct flink_device* parent;
    u8                   id;
    u16                  type_id;
    u8                   sub_type_id;
    u8                   if_version;
    u32                  base_addr;
    u32                  mem_size;
    u32                  nof_channels;
};

The following picture shows an example of a system with two flink devices, each containing two subdevices.

Obviously, a flink device must communicate with a given set of operations over its interface. However, we do not want to introduce any hardware dependency into flink_core.c. For this purpose we define a structure flink_bus_ops.

// ############ flink bus operations ############
struct flink_bus_ops {
    u8  (*read8)(struct flink_device*, u32 addr);
    u16 (*read16)(struct flink_device*, u32 addr);
    u32 (*read32)(struct flink_device*, u32 addr);
    int (*write8)(struct flink_device*, u32 addr, u8 val);
    int (*write16)(struct flink_device*, u32 addr, u16 val);
    int (*write32)(struct flink_device*, u32 addr, u32 val);
    u32 (*address_space_size)(struct flink_device*);
};

This bus operations will later point to interface dependent functions. There is one more important data structure:

// ############ flink private data ############
struct flink_private_data {
    struct flink_device*    fdev;
    struct flink_subdevice* current_subdevice;
};

An oben file is represented in Linux by the file structure. A parameter of type file is passed when calling read or write operations. file contains a field private_data which is used here to point to flink_private_data and holds the information about which device and subdevice will be targeted.

File Operations

A flink device implements the following file operations

• open
• release
• read
• write
• ioctl
• llseek

Device and Subdevice Management

Several functions to manage devices and subdevices are exported for use in other kernel modules. The API can be found in API