linux-kernel - Re: [PATCH v3 1/3] driver-core: return EINVAL error instead of BUG

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Message-ID: <20180515151035.GB23553@kroah.com>
Date:   Tue, 15 May 2018 17:10:35 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Florian Schmaus <flo@...kplace.eu>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] driver-core: return EINVAL error instead of
 BUG_ON()

On Tue, May 15, 2018 at 03:51:12PM +0200, Florian Schmaus wrote:
> I triggerd the BUG_ON() in driver_register() when booting a domU Xen
> domain. Since there was no contextual information logged, I needed to
> attach kgdb to determine the culprit (the wmi-bmof driver in my
> case). The BUG_ON() was added in commit f48f3febb2cb ("driver-core: do
> not register a driver with bus_type not registered").
> 
> Instead of running into a BUG_ON() we print an error message
> identifying the, likely faulty, driver but continue booting.
> 
> Signed-off-by: Florian Schmaus <flo@...kplace.eu>
> ---
> 
> Notes:
>     - return EINVAL (instead of EBUSY)
>     - follow common pattern when quoting commits in commit messages
> 
>  drivers/base/driver.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/driver.c b/drivers/base/driver.c
> index ba912558a510..afd5b08b7677 100644
> --- a/drivers/base/driver.c
> +++ b/drivers/base/driver.c
> @@ -148,7 +148,11 @@ int driver_register(struct device_driver *drv)
>  	int ret;
>  	struct device_driver *other;
>  
> -	BUG_ON(!drv->bus->p);
> +	if (!drv->bus->p) {
> +		printk(KERN_ERR "Driver '%s' was unable to register bus_type\n",
> +			   drv->name);

checkpatch.pl should have said to use pr_err(), right?  :)

Also, why not print out the driver name as well?

thanks,

greg k-h