C Struct

[Balroj]

Hi,

I was taking a look at the linux kernel source, and find this struc:

Code: Select all

struct consw {
const char *(*con_startup)(void);
void (*con_init)(struct vc_data *, int);
void (*con_deinit)(struct vc_data *);
void (*con_clear)(struct vc_data *, int, int, int, int);
void (*con_putc)(struct vc_data *, int, int, int);
void (*con_putcs)(struct vc_data *,const unsigned short *,int ,int ,int);
void (*con_cursor)(struct vc_data *, int);
int (*con_scroll)(struct vc_data *, int, int, int, int);
.....

But i don't understand it well, void (*con_init)(struct vc_data *, int);i don't understand this. Can anyone please explain it?

thanks.

[anubis]

Hi,
con_init is a function asscociated with console initialization.

vc_data is a structure containig the properties regarding the console.

using vc_data, con_init initializes the console. i am not sure what the other parameter(int) in con_init refer to...

[be]

I think this is a function pointers, some pointer assigned to a function, and then this function called not by name, but by the pointer. ::)

[TB]

void (*con_init)(struct vc_data *, int);

Yes, it's pointer to a function with (struct vc_data *, int) as parameters.
So, you would do something like:
con_init = (address of the function) and then you can do things like con_init(&data, 123);

[Pype.Clicker]

basically, this technique provide something looking like polymorphism in C: you can define how a console is initialized by setting the right function as console.con_init=f and then call it with something like console_ptr->con_init(data,int)

[df]

good for dirvers / vfs interfaces etc