Date: Sat, 06 May 2000 12:58:10 -0700 From: Jake Burkholder <jburkhol@home.com> To: Alexander Langer <alex@big.endian.de> Cc: hackers@FreeBSD.ORG Subject: Re: problem with ioctl handler in a module Message-ID: <20000506195810.31B4ABCA7@io.yi.org> In-Reply-To: Message from Alexander Langer <alex@big.endian.de> of "Sat, 06 May 2000 20:09:40 %2B0200." <20000506200940.A8087@cichlids.cichlids.com>
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> Hello!
>
> I have:
>
> int ziva_ioctl(dev_t dev, u_long cmd, caddr_t arg, int flag, struct
> proc* pr)
>
> when this function catches a ioctl from userspace, called as:
> int foo = 199;
> ioctl(fd, 10, &foo);
>
> the u_long cmd contains 10, which is correct (so the ioctl-handler is
> called correctly).
>
> However, I can't get the value of the int.
>
> I tried something like:
> if (*((int *) arg) == 199)
> <bleh>.
>
> But this doesn't work, <bleh> is not executed. Somehow, I can't access
> the memory this way.
>
> Anyone knows, what I'm doing wrong?
The request parameter to ioctl needs to contain length information.
I think you want something like:
#define ZIVA_IOCTL _IOW('c', 10, int)
int foo = 199;
ioctl(fd, ZIVA_IOCTL, &foo);
Then arg should be right. See iocomm.h.
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