linux-kernel - Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

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Message-ID: <20150520212235.GA20943@psi-dev26.jf.intel.com>
Date:	Wed, 20 May 2015 14:22:36 -0700
From:	David Cohen <david.a.cohen@...ux.intel.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	balbi@...com
Subject: Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

Hi,

On Wed, May 20, 2015 at 03:33:26PM -0400, Sasha Levin wrote:
> ULPI registers it's bus at module_init so if the bus fails to register, the

A minor comment: s/it's/its/

> module will fail to load and all will be well in the world.
> 
> However, if the ULPI code is built-in rather than a module, the bus
> initialization may fail but we'd still try to register drivers later onto
> a non-existant bus, which will panic the kernel.
> 
> Fix that by checking that the bus was indeed initialized before trying to
> register drivers on top of it.
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> ---
>  drivers/usb/common/ulpi.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/common/ulpi.c b/drivers/usb/common/ulpi.c
> index 0e6f968..0b0a5e7 100644
> --- a/drivers/usb/common/ulpi.c
> +++ b/drivers/usb/common/ulpi.c
> @@ -132,6 +132,10 @@ int ulpi_register_driver(struct ulpi_driver *drv)
>  	if (!drv->probe)
>  		return -EINVAL;
>  
> +	/* Was the bus registered successfully? */
> +	if (!ulpi_bus.p)
> +		return -ENODEV;
> +

Good catch. Otherwise it may trigger BUG() on driver_register().
I wonder if it would be nice to have a macro for that checking :)

Anyway,

Reviewed-by: David Cohen <david.a.cohen@...ux.intel.com>

>  	drv->driver.bus = &ulpi_bus;
>  
>  	return driver_register(&drv->driver);
> -- 
> 1.7.10.4
> 
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