linux-kernel - Re: [PATCH] driver core: check bus->match without holding device lock(v2)

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Date:	Fri, 10 Apr 2009 17:31:24 +0200
From:	Andreas Schwab <schwab@...ux-m68k.org>
To:	tom.leiming@...il.com
Cc:	kay.sievers@...y.org, greg@...ah.com, cornelia.huck@...ibm.com,
	linux-kernel@...r.kernel.org, arjan@...ux.intel.com
Subject: Re: [PATCH] driver core: check bus->match without holding device lock(v2)

tom.leiming@...il.com writes:

> +static inline int driver_match_device(struct device_driver *drv,
> +				      struct device *dev)
> +{
> +	return drv->bus->match && drv->bus->match(dev, drv);
> +}

This logic is wrong.  !(a && !b) <=> !a || b, not a && b

A bus that does not have a match function now never matches, whereas
previously it would always match.  This breaks aoa-soundbus.

Andreas.
---
driver core: Fix logic in driver_match_device

A bus that does not have a match function always matches.  This fixes
49b420a13ff9 ("driver core: check bus->match without holding device
lock").

Signed-off-by: Andreas Schwab <schwab@...ux-m68k.org>
---
 drivers/base/base.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/base.h b/drivers/base/base.h
index ddc9749..087e911 100644
--- a/drivers/base/base.h
+++ b/drivers/base/base.h
@@ -115,7 +115,7 @@ extern int driver_probe_device(struct device_driver *drv, struct device *dev);
 static inline int driver_match_device(struct device_driver *drv,
 				      struct device *dev)
 {
-	return drv->bus->match && drv->bus->match(dev, drv);
+	return !drv->bus->match || drv->bus->match(dev, drv);
 }
 
 extern void sysdev_shutdown(void);

-- 
Andreas Schwab, schwab@...ux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
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