From: Russell King <rmk+lkml@arm.linux.org.uk>
To: Michael Hanselmann <linux-kernel@hansmi.ch>
Cc: linux-serial@vger.kernel.org
Subject: Re: Hang in uart_block_til_ready()
Date: Sun, 2 Apr 2006 15:38:27 +0100 [thread overview]
Message-ID: <20060402143827.GA3565@flint.arm.linux.org.uk> (raw)
In-Reply-To: <20060402135138.GC2954@hansmi.ch>
On Sun, Apr 02, 2006 at 03:51:38PM +0200, Michael Hanselmann wrote:
> I've discovered a problem where I'm not sure wether it's an error in the
> kernel or in the hardware.
It's neither - it's a bug in your test program. If you want "callout"
semantics, open the port using O_NONBLOCK mode.
If you don't open the port using O_NONBLOCK then the port will wait for
the DCD line (or virtual DCD line) to be asserted by the hardware before
exiting uart_block_til_ready(). This is used for gettys on UARTs so
they don't display the login banner until someone connects to the port.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
next prev parent reply other threads:[~2006-04-02 14:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-02 13:51 Hang in uart_block_til_ready() Michael Hanselmann
2006-04-02 14:38 ` Russell King [this message]
2006-04-02 15:17 ` Michael Hanselmann
2006-04-02 15:23 ` Russell King
2006-04-02 15:42 ` Michael Hanselmann
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