Visible to Intel only — GUID: mwh1416946821361
Ixiasoft
Visible to Intel only — GUID: mwh1416946821361
Ixiasoft
8.7.1.1. Create a Device Instance
For a device to be made available as a character mode device, it must provide an instance of the alt_dev structure. The alt_dev structure, defined in < Nios® II EDS install path>/components/altera_hal/HAL/inc/sys/alt_dev.h, is essentially a collection of function pointers. These functions are called in response to application accesses to the HAL file system. For example, if you call the function open() with a file name that corresponds to this device, the result is a call to the open() function provided in this structure.
Example 7–1. alt_dev Structure
typedef struct { alt_llist llist; /* for internal use */ const char* name; int (*open) (alt_fd* fd, const char* name, int flags, int mode); int (*close) (alt_fd* fd); int (*read) (alt_fd* fd, char* ptr, int len); int (*write) (alt_fd* fd, const char* ptr, int len); int (*lseek) (alt_fd* fd, int ptr, int dir); int (*fstat) (alt_fd* fd, struct stat* buf); int (*ioctl) (alt_fd* fd, int req, void* arg); } alt_dev;
For more information about open(), close(), read(), write(), lseek(), fstat(), and ioctl(), refer to the "HAL API Reference" section.
Section Content
Modifying the Global Error Status, errno
Default Behavior for Functions Defined in alt_dev