From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4A9E8437.80900@domain.hid> Date: Wed, 02 Sep 2009 16:41:59 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <4A9E3AAB.2070404@domain.hid> <4A9E4D84.20602@domain.hid> <4A9E5424.9070500@domain.hid> <4A9E5917.8060200@domain.hid> <1251895278.3205.190.camel@domain.hid> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Deprecated kernel system calls in xenomai-head and new application development paradigm List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Rus V. Brushkoff" Cc: Xenomai help Rus V. Brushkoff wrote: > On Wed, 2 Sep 2009, Philippe Gerum wrote: > > :> Next - I do not > :> understand why the previous model lets the _developer_ itself decide > :> which of the application tasks will be running in kernel and which will > :> be running in user space. The current model left the people without any > :> choice. So the current model itself decided instead of developer what is > :> better - I think this is wrong. > : > :With that kind of reasoning, you would keep on coding your RT > :application fully in kernel space, but we made some progress since 1997, > :fortunately. > > Sorry, but device drivers for hardware that need RT processing can't be > written in user space. Dealing with interrupts, PCI, DMA, I/O ports can > be done only in kernel space. So it is not possible to decide at the > Xenomai architect level wich driver task are optimal to run in which mode > - it will depends from the particular development problem area. > So I think that forcing people to write the RT tasks only in user space > will make unneded latencies, which will be inserted by data passing > between user and kernel domains. > Next: the traditional and clean Unix programming concept suppose that > user space applications are simple and operate on the files/pipes that > are attached to kernel drivers. It will be better to leave this concept > live as it proved its architect efficiency. You misunderstand us. We tell you that you should develop drivers in kernel-space, using the RTDM skin. The RTDM skin is made to resemble the Linux driver model, so that it will make your drivers easily portable to vanilla linux. -- Gilles