Subject: Problem with ioctl command TCGETS
From: Ozan Eren Bilgen <oebilgen@uekae.tubitak.gov.tr>
To: Linux Kernel Maillist <linux-kernel@vger.kernel.org>
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Organization: TUBITAK - Ulusal Elektronik ve Kriptoloji Arastirma Enstitusu
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Date: Sun, 28 Nov 2004 02:22:51 +0200
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Message-Id: <20041128002044.CE13839877@uekae.uekae.gov.tr>
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--- Please CC me your responses ---


Hi,

While tracking KPPP and modem interaction, I experienced a problem with
TCGETS ioctl command, which is defined as constant number 0x5401 in
"include/asm/ioctls.h".  If you decode TCGETS, you will obtain:

	type: 'T'
 	direction: _IOC_NONE
	number: 1
	size: 0

but applications (like KPPP) cause indirectly that the modem descriptor
is ioctl'd by passing a string, as the example in
http://www.ussg.iu.edu/hypermail/linux/kernel/9904.0/0371.html shows: 

	fd = open("/dev/ttyS1", O_RDWR|O_NONBLOCK)
	fcntl(fd, F_GETFD)
	fcntl(fd, F_SETFD, FD_CLOEXEC)
	fcntl(fd, F_GETFL)
	ioctl(fd, TCGETS, {B9600 opost isig icanon echo ...}) = 0
	
CMIIW, TCGETS ioctl command should not interest with its argp, but
drivers/char/tty_ioctl.c does.

	case TCGETS:
		if (kernel_termios_to_user_termios((struct termios __user *)arg,
real_tty->termios))
			return -EFAULT;
		return 0;

I have a few questions:

1. Is it nice to break _IO macros?
2. If it has a historical reason, shall I forget to trust to the
informations that I decoded using _IO* macros?
3. Is there a list of such amazing commands?


Thanks in advance,
Ozan Eren BILGEN


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