RE: how to use the function copyout()

From: Felix-KM (Felix-KM_at_yandex.ru)
Date: 07/26/05

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    Date: Tue, 26 Jul 2005 11:46:23 +0400 (MSD)
To: NKoch@demig.de

    > I think that could work (only an idea, not tested):
    >
    >
    > struct Region
    > {
    > void * p;
    > size_t s;
    > };
    >
    >
    > #define IOBIG _IOWR ('b', 123, struct Region)
    >
    >
    > userland:
    >
    > char data[1000];
    > struct Region r;
    >
    > r.p = data;
    > r.s = sizeof data;
    > int error = ioctl (fd, IOBIG, &r);
    >
    >
    > kernel:
    > int my_ioctl(..., caddr_t data, ...)
    > {
    > ...
    > char data[1000];
    > ...
    > return copyout(data, ((struct Region *) data)->p, ((struct Region *)
    > data)->s);
    > }
    >
    >
    > Have a try and tell us if it works.
    >
    >
    > Norbert
    >

    Yes! Now the program works!
    I have changed the code in this way:

    struct Region
    {
      void * p;
      size_t s;
    };

    #define IOBIG _IOWR ('b', 123, struct Region)

    ---- driver ----

    struct my_softc {
     ...
     short unsigned int B;
    };

    ...

    static int
    my_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int flag,
                                                   struct thread *td)
    {
     struct my_softc *my_sc;
     int unit, error;
     unit = minor(dev);
     
     my_sc = (struct my_softc *)devclass_get_softc(my_devclass, unit);
     if (my_sc == NULL)
       return (ENXIO);
     
     switch(cmd)
     {
       ...
       case IOCTL_GET_B:
         error = copyout(&my_sc->B, (((struct Datas *)data)->d)+0x1850, sizeof(my_sc->B));
         break;
       default:
         break;
     }
        return 0;
    }

    ---user program ----------------------

    ...

    short unsigned int data[32768];
    struct Region r;

    int
    main(int argc, char *argv[])
    {
     ...

     r.p = data;
     r.s = sizeof data;
     
     if (ioctl(fd0, IOCTL_GET_B, &r) == -1)
       err(1, "IOCTL_GET_B");

     ...
    }

    Now I have access to each element of the array (e.g. 0x1850).
    Thank you very much!
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