linux-kernel - Re: [PATCH v3] base/platform: fix binding for drivers without probe callback

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Message-ID: <20151203090023.GZ5072@pengutronix.de>
Date:	Thu, 3 Dec 2015 10:00:23 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	martin.wilck@...fujitsu.com
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	tpmdd-devel@...ts.sourceforge.net
Subject: Re: [PATCH v3] base/platform: fix binding for drivers without probe
 callback

Hello Martin,

On Thu, Dec 03, 2015 at 09:51:44AM +0100, martin.wilck@...fujitsu.com wrote:
> From: Martin Wilck <Martin.Wilck@...fujitsu.com>
> 
> Since b8b2c7d845d5, platform_drv_probe() is called for all platform
> devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
> platform_drv_probe() will return the error code from dev_pm_domain_attach().
> 
> This causes real_probe() to enter the "probe_failed" path and set
> dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
> success if both dev->bus->probe and drv->probe were missing. As a result,
> a device and driver could be "bound" together just by matching their names;
> this doesn't work any more after b8b2c7d845d5.
> 
> This change broke the assumptions of certain drivers; for example, the TPM
> code has long assumed that platform driver and device with matching name
> could be bound in this way. That assumption may cause such drivers to
> fail with Oops during initialization after applying this change. Failure
> in suspend/resume tests under qemu has also been reported.
> 
> This patch restores the previous (4.3.0 and earlier) behavior of
> platform_drv_probe() in the case when the associated platform driver has
> no "probe" function.
> 
> Fixes: b8b2c7d845d5 ("base/platform: assert that dev_pm_domain callbacks are called unconditionally")
> Signed-off-by: Martin Wilck <Martin.Wilck@...fujitsu.com>

Acked-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

Thanks
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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