From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1aG0wM-0005Nz-4M for barebox@lists.infradead.org; Mon, 04 Jan 2016 08:56:35 +0000 Date: Mon, 4 Jan 2016 09:56:11 +0100 From: Sascha Hauer Message-ID: <20160104085611.GC13058@pengutronix.de> References: <20151223191058.4ffb07f4@berta> <20151223163532.GA1068@omega> <20151223195644.73537fb9@berta> <20151223170438.GA3791@omega> <20151224124837.0fcc6fce@berta> <20151224164225.25665d7f@berta> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20151224164225.25665d7f@berta> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [RFC] device probe order To: Peter Mamonov Cc: barebox On Thu, Dec 24, 2015 at 04:42:25PM +0300, Peter Mamonov wrote: > On Thu, 24 Dec 2015 12:48:37 +0300 > Peter Mamonov wrote: > > > On Wed, 23 Dec 2015 18:04:43 +0100 > > Alexander Aring wrote: > > > > > On Wed, Dec 23, 2015 at 07:56:44PM +0300, Peter Mamonov wrote: > > > > On Wed, 23 Dec 2015 17:35:51 +0100 > > > > Alexander Aring 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? > > > > > > > > > > mhhh, maybe a simple "get_device_by_name" works here. > > > > > > If returning NULL then return -EPROBE_DEFER. Don't know if this is a > > > good solution, name need to be unique then. > > > > > > > > > btw: > > > Just found that "of_find_device_by_node" returns -EPROBE_DEFER when > > > nothing was found. This was introduced by the patch series. > > > > I like this approach better, than introducing a global variable. > > Will look further into it. > > Unfortunately of_find_device_by_node() returns a valid pointer to > the device before the device probe function is called. I guess > get_device_by_name() behaves in the same way. This looks buggy. There should be a way to tell if a device has been probed or not before working with the device returned by of_find_device_by_node() or get_device_by_name(). The easiest way is probably to check for dev->driver. This is not enough though to tell if the device probe has failed, not yet executed, or deferred. Maybe we could store the probe status of a device in struct device_d itself. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox