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authorDavid Brownell <david-b@pacbell.net>2007-05-08 03:29:39 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 14:15:10 -0400
commit49a4ec188f9a96c9a5567956718213d38a456a19 (patch)
tree29ac9f610ed355b3e3f752206c03180054df9bd7 /drivers/base/platform.c
parenteb81d93046e7de51d47b8f1303d80e6f51ac9e33 (diff)
fix hotplug for legacy platform drivers
We've had various reports of some legacy "probe the hardware" style platform drivers having nasty problems with hotplug support. The core issue is that those legacy drivers don't fully conform to the driver model. They assume a role that should be the responsibility of infrastructure code: creating device nodes. The "modprobe" step in hotplugging relies on drivers to have split those roles into different modules. The lack of this split causes the problems. When a driver creates nodes for devices that don't exist (sending a hotplug event), then exits (aborting one modprobe) before the "modprobe $MODALIAS" step completes (by failing, since it's in the middle of a modprobe), the result can be an endless loop of modprobe invocations ... badness. This fix uses the newish per-device flag controlling issuance of "add" events. (A previous version of this patch used a per-device "driver can hotplug" flag, which only scrubbed $MODALIAS from the environment rather than suppressing the entire hotplug event.) It also shrinks that flag to one bit, saving a word in "struct device". So the net of this patch is removing some nasty failures with legacy drivers, while retaining hotplug capability for the majority of platform drivers. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Greg KH <gregkh@suse.de> Cc: Andres Salomon <dilinger@debian.org> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/base/platform.c')
-rw-r--r--drivers/base/platform.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 17b5ece8f82c..eb84d9d44645 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -160,6 +160,11 @@ static void platform_device_release(struct device *dev)
160 * 160 *
161 * Create a platform device object which can have other objects attached 161 * Create a platform device object which can have other objects attached
162 * to it, and which will have attached objects freed when it is released. 162 * to it, and which will have attached objects freed when it is released.
163 *
164 * This device will be marked as not supporting hotpluggable drivers; no
165 * device add/remove uevents will be generated. In the unusual case that
166 * the device isn't being dynamically allocated as a legacy "probe the
167 * hardware" driver, infrastructure code should reverse this marking.
163 */ 168 */
164struct platform_device *platform_device_alloc(const char *name, unsigned int id) 169struct platform_device *platform_device_alloc(const char *name, unsigned int id)
165{ 170{
@@ -172,6 +177,12 @@ struct platform_device *platform_device_alloc(const char *name, unsigned int id)
172 pa->pdev.id = id; 177 pa->pdev.id = id;
173 device_initialize(&pa->pdev.dev); 178 device_initialize(&pa->pdev.dev);
174 pa->pdev.dev.release = platform_device_release; 179 pa->pdev.dev.release = platform_device_release;
180
181 /* prevent hotplug "modprobe $(MODALIAS)" from causing trouble in
182 * legacy probe-the-hardware drivers, which don't properly split
183 * out device enumeration logic from drivers.
184 */
185 pa->pdev.dev.uevent_suppress = 1;
175 } 186 }
176 187
177 return pa ? &pa->pdev : NULL; 188 return pa ? &pa->pdev : NULL;
@@ -351,6 +362,13 @@ EXPORT_SYMBOL_GPL(platform_device_unregister);
351 * memory allocated for the device allows drivers using such devices 362 * memory allocated for the device allows drivers using such devices
352 * to be unloaded iwithout waiting for the last reference to the device 363 * to be unloaded iwithout waiting for the last reference to the device
353 * to be dropped. 364 * to be dropped.
365 *
366 * This interface is primarily intended for use with legacy drivers
367 * which probe hardware directly. Because such drivers create sysfs
368 * device nodes themselves, rather than letting system infrastructure
369 * handle such device enumeration tasks, they don't fully conform to
370 * the Linux driver model. In particular, when such drivers are built
371 * as modules, they can't be "hotplugged".
354 */ 372 */
355struct platform_device *platform_device_register_simple(char *name, unsigned int id, 373struct platform_device *platform_device_register_simple(char *name, unsigned int id,
356 struct resource *res, unsigned int num) 374 struct resource *res, unsigned int num)