linux-kernel - Re: [PATCH v2] parport: register driver later

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Date:	Mon, 7 Mar 2016 10:32:55 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH v2] parport: register driver later

On Sun, Mar 06, 2016 at 08:40:10PM +0530, Sudip Mukherjee wrote:
> If the parport bus is not yet registered and any device using parallel
> port tries to register with the bus we get a stackdump with a message
> of Kernel bug.
> 
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Cc: <stable@...r.kernel.org> # 4.2+
> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
> ---
> 
> Hi Ross,
> Can you please test this patch in your setup. This is a respin of the
> previous patch in another way.

Yep, this also solves the issue for me.

Tested-by: Ross Zwisler <ross.zwisler@...ux.intel.com>

>  drivers/parport/share.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/parport/share.c b/drivers/parport/share.c
> index 3308427..c1eba80 100644
> --- a/drivers/parport/share.c
> +++ b/drivers/parport/share.c
> @@ -135,9 +135,18 @@ static struct bus_type parport_bus_type = {
>  	.probe = parport_probe,
>  };
>  
> +static bool is_registered;
> +
>  int parport_bus_init(void)
>  {
> -	return bus_register(&parport_bus_type);
> +	int ret;
> +
> +	ret = bus_register(&parport_bus_type);
> +	if (ret)
> +		return ret;
> +
> +	is_registered = true;
> +	return 0;
>  }
>  
>  void parport_bus_exit(void)
> @@ -273,6 +282,9 @@ int __parport_register_driver(struct parport_driver *drv, struct module *owner,
>  		/* using device model */
>  		int ret;
>  
> +		if (!is_registered)
> +			return -EAGAIN;
> +
>  		/* initialize common driver fields */
>  		drv->driver.name = drv->name;
>  		drv->driver.bus = &parport_bus_type;
> -- 
> 1.9.1