linux-kernel - Re: [RFC] cycle timer read extension for raw1394/libraw1394

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Date:	Sat, 27 Jan 2007 13:48:51 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Pieter Palmers <pieterp@...w.be>
CC:	linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [RFC] cycle timer read extension for raw1394/libraw1394

Pieter Palmers wrote:
> Stefan Richter wrote:
>> Thus?
>>     preempt_disable();
>>     local_irq_save(flags);
>>
>>     read_cycle_timer;
>>     read_time_of_day;
>>
>>     local_irq_restore(flags);
>>     preempt_enable();
>>
>> in hpsb_read_cycle_timer.
> My main issue was that I still had to figure out how to do this... I'm a
>  very occasional kernel space programmer.

Unfortunately me too, and the level of ieee1394 driver maintenance shows it.

> Thanks for the hint, I'll do it like this.
> 
> I still have to check if I don't introduce a too long non-preemptible
> path though.

It's a simple MMIO read (readl) and the do_gettimeofday, which should be
fine.
-- 
Stefan Richter
-=====-=-=== ---= ==-==
http://arcgraph.de/sr/
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