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Date: Wed, 23 Dec 2015 19:56:44 +0300
From: Peter Mamonov <pmamonov@gmail.com>
Message-ID: <20151223195644.73537fb9@berta>
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Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org
Subject: Re: [RFC] device probe order
To: Alexander Aring <alex.aring@gmail.com>, Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox <barebox@lists.infradead.org>

On Wed, 23 Dec 2015 17:35:51 +0100
Alexander Aring <alex.aring@gmail.com> wrote:

> On Wed, Dec 23, 2015 at 07:10:58PM +0300, Peter Mamonov wrote:
> > Dear All,
> > 
> > I've ported an UHCI driver from the u-boot to the barebox (WIP). To
> > interoperate with the EHCI driver, the UHCI driver should be probed
> > ater the EHCI driver. Both drivers are binded via the device tree
> > mechanism. How can i achieve the correct probe order?
> > 
> 
> Normally this should done by returning "-EPROBE_DEFER" inside the
> probe function. There was some RFC last years for supporting
> EPROBE_DEFER [0] and it seems these are mainline.
> 
> However you need some bool which indicates that the EHCI driver is
> probed.

Thanks, Alex. As i understand, this is the linux-way solution.

Sasha, is it ok to add a global variable to indicate the EHCI presence?
Or should we follow the way proposed by the mentioned RFCs, i.e.
introduce dependencies between drivers?

> 
> int uhci_probe(foobar) {
> 
> if (!indicate_ehci_is_probed(foobar)
> 	return -EPROBE_DEFER;
> }
> 
> - Alex
> 
> [0]
> http://barebox.infradead.narkive.com/ZWIXXU0R/patch-v2-0-6-introduce-deferred-probing


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