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Message-ID: <4D9486E4.9030006@monstr.eu>
Date: Thu, 31 Mar 2011 15:51:32 +0200
From: Michal Simek <monstr@monstr.eu>
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To: Arnd Bergmann <arnd@arndb.de>
CC: John Williams <john.williams@petalogix.com>,
        Wolfram Sang <w.sang@pengutronix.de>,
        devicetree-discuss@lists.ozlabs.org, grant.likely@secretlab.ca,
        linux-kernel@vger.kernel.org, hjk@linutronix.de, gregkh@suse.de
Subject: Re: [PATCH] uio/pdrv_genirq: Add OF support
References: <1301574600-4861-1-git-send-email-monstr@monstr.eu> <20110331124925.GA2202@pengutronix.de> <AANLkTinJrG=s3Xuvf_=bNtYF-z8u+YXvd217UKKz24ik@mail.gmail.com> <201103311525.52396.arnd@arndb.de>
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Arnd Bergmann wrote:
> On Thursday 31 March 2011, John Williams wrote:
>> On Thu, Mar 31, 2011 at 10:49 PM, Wolfram Sang <w.sang@pengutronix.de> wrote:
>>> On Thu, Mar 31, 2011 at 02:30:00PM +0200, Michal Simek wrote:
>>>> Support OF support. "generic-uio" compatible property is used.
>>> And exactly this was the issue last time (when I tried). This is a
>>> generic property, which is linux-specific and not describing HW. The
>>> agreement back then was to we probably need to add compatible-entries at
>>> runtime (something like new_id for USB). So the uio-of-driver could be
>>> matched against any device. Otherwise, we would collect a lot of
>>> potential entries like "vendor,special-card1". Although I wonder
>>> meanwhile if it is really going to be that bad; we don't have so much
>>> UIO-driver in tree as well. Maybe worth a try?
>>
>> Maybe I misunderstand you, in my view it is the responsibility of
>> <vendor> to create their DTS files to indicate they want
>> <special-card1> to bind to generic-uio.
>>
>> So, no great list of compat strings should grow in the driver, but
>> rather the user of the driver must make it happen.
>>
>> Am I missing something?
> 
> We try to make the device tree on describe the present hardware,
> but not relate to how it is used.
> 
> There are certainly cases where a specific piece of hardware can
> be used either by a kernel-only driver or the UIO driver with a
> user backend. I would argue that you should be able to use an
> identical device tree for both cases, because the hardware is
> the same. Chosing which driver to use can be either in the realm
> of the kernel, or even user policy.

ok. What about to keep of_device_id empty?  Then there is compatible property 
string and everybody can choose what wants.
OF is just a different driver initialization method but it is in the same 
category which is supported right now which is initialization through 
platform_device structure.

Michal

-- 
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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