linux-kernel - Re: [PATCH 3/7] ark3116: (3rd try) Replace cmget

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Date:	Sun, 25 Oct 2009 20:56:36 +0100
From:	Bart Hartgers <bart.hartgers@...il.com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] ark3116: (3rd try) Replace cmget

2009/10/25 Oliver Neukum <oliver@...kum.org>:
> Am Sonntag, 25. Oktober 2009 18:51:00 schrieb bart.hartgers@...il.com:
>> +       /* read modem status */
>> +       unsigned status = atomic_read(&priv->msr);
>> +       /* modem control is output */
>> +       unsigned ctrl = atomic_read(&priv->mcr);
>
> What is the sense of having two atomic variables?
> You can get races where one is changed but the other is not.
>
>        Regards
>                Oliver
>
>

Hi Oliver,

I don't think so. The two values are not really related.

These are two separate things: mcr (modem control reg) is ultimately
changed by whatever has the serial port open, msr (modem status
register) represents the status of the handshaking lines, and is
changed (via the interrupt urb callback) by hardware.

Groeten,
Bart

-- 
Bart Hartgers - New e-mail: bart.hartgers@...il.com
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