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Date: Fri, 02 Apr 2010 12:39:26 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-core] [Xenomai-help] Analogy cmd_write example
	explanation
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: Alexis Berlemont <berlemont.hauw@domain.hid>, xenomai-core <xenomai@xenomai.org>

Redirecting to xenomai core.

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Because of __xn_exec_current, people have broken drivers, and user-space
>> applications using T_PRIMARY as a broken way to workaround these broken
>> drivers, and by maintaining compatibility, we let them keep their broken
>> drivers and applications, by changing to the more natural
>> __xn_exec_conforming and removing T_PRIMARY, we ask them to fix their
>> drivers and applications.
> 
> Right goal, wrong approach for the reason I pointed out to Philippe:
> 
> We cannot map all kinds of driver requirements on a single
> __xn_exec_current in the RTDM middle layer.

What requirement can we not handle? It looks to me like with
__xn_exec_conforming, we can handle any requirement.

The only problem being the "double context switch" issue. But as
Philippe said, a sane application is calling such ioctls from non
critical code, so this is in fact a non-issue.

-- 
					    Gilles.