Date: Wed, 28 Sep 2005 21:47:49 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: nsrashmi@gmail.com Cc: freebsd-hackers@freebsd.org, bugi@lists.redbrick.dcu.ie Subject: Re: Message-ID: <20050928.214749.111484152.imp@bsdimp.com> In-Reply-To: <9f9993160509280045586fb14d@mail.gmail.com> References: <9f99931605092800402dd1db9a@mail.gmail.com> <9f9993160509280045586fb14d@mail.gmail.com>
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In message: <9f9993160509280045586fb14d@mail.gmail.com>
rashmi ns <nsrashmi@gmail.com> writes:
: Hello All ,
: I was trying to add a new ioctl cnd like
: #define HDLCMODE _IOR('6',0xF,int)
: when i try to uprintf the data which was sent from the user-space in the
: device-driver-ioctl-routine i'll get a different value than which is passed.
: Can anybody please tell me why this is happening . I pass the address of
: integer from the user space as third arg to the ioctl call .
: thanks and regards,
Remember that there's a level of indirection here. For the userland
call, you'll have something like:
int i = 10;
ioctl (fd, HDLCMODE, &i);
in the kernel, this translates into a call to the driver's ioctl
routine:
int
fooioctl(struct cdev *tp, u_long cmd, void *data, int flag, struct thread *t)
{
switch (cmd)
{
case HDLCMODE:
printf("this should be 10: %d\n", *(int *)data);
break;
}
Warner
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