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Date: Thu, 28 May 2015 11:09:38 +0530
From: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Tal Shorer <tal.shorer@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        USB list <linux-usb@vger.kernel.org>,
        "<linux-kernel@vger.kernel.org>" <linux-kernel@vger.kernel.org>,
        David Cohen <david.a.cohen@linux.intel.com>,
        Felipe Balbi <balbi@ti.com>, Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist
Message-ID: <20150528053938.GB2944@sudip-PC>
References: <20150527083933.GA13844@kuha.fi.intel.com>
 <Pine.LNX.4.44L0.1505271109450.1540-100000@iolanthe.rowland.org>
 <20150527152116.GA1972@kroah.com>
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On Wed, May 27, 2015 at 08:21:16AM -0700, Greg KH wrote:
> On Wed, May 27, 2015 at 11:16:34AM -0400, Alan Stern wrote:
> > On Wed, 27 May 2015, Heikki Krogerus wrote:
> 
> Maybe we need to test for this in the driver core, not allowing drivers
> for busses that are not registered, that might solve the main problem
> here.  I'll try to look at it tonight.
may i suggest something like this ?
buildtest with allmodconfig and allyesconfig on x86_64.
built and booted on x86.


diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 5005924..95cefa0 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -943,6 +943,7 @@ int bus_register(struct bus_type *bus)
 	if (retval)
 		goto bus_groups_fail;
 
+	bus->registered = true;
 	pr_debug("bus: '%s': registered\n", bus->name);
 	return 0;
 
diff --git a/drivers/base/driver.c b/drivers/base/driver.c
index 4eabfe2..1acae5b 100644
--- a/drivers/base/driver.c
+++ b/drivers/base/driver.c
@@ -150,6 +150,11 @@ int driver_register(struct device_driver *drv)
 	int ret;
 	struct device_driver *other;
 
+	if (!drv->bus->registered) {
+		pr_err("Driver %s registration failed. bus not yet registered\n",
+		       drv->name);
+		return -ENODEV;
+	}
 	BUG_ON(!drv->bus->p);
 
 	if ((drv->bus->probe && drv->probe) ||
diff --git a/include/linux/device.h b/include/linux/device.h
index 00ac57c..8fe4745 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -126,6 +126,7 @@ struct bus_type {
 	const struct dev_pm_ops *pm;
 
 	const struct iommu_ops *iommu_ops;
+	bool registered;	/* DON'T TOUCH THIS */
 
 	struct subsys_private *p;
 	struct lock_class_key lock_key;


regards
sudip
> 
> thanks,
> 
> greg k-h