linux-kernel - Re: [PATCH] usb: usb_phy_gen: refine conditional declaration of usb_nop_xceiv

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Date:	Thu, 17 Oct 2013 13:25:48 -0400
From:	Josh Boyer <jwboyer@...hat.com>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] usb: usb_phy_gen: refine conditional declaration of
 usb_nop_xceiv_register

On Wed, Oct 16, 2013 at 07:18:41PM -0700, Guenter Roeck wrote:
> Commit 3fa4d734 (usb: phy: rename nop_usb_xceiv => usb_phy_gen_xceiv)
> changed the conditional around the declaration of usb_nop_xceiv_register
> from
> 	#if defined(CONFIG_NOP_USB_XCEIV) ||
> 		(defined(CONFIG_NOP_USB_XCEIV_MODULE) && defined(MODULE))
> to
> 	#if IS_ENABLED(CONFIG_NOP_USB_XCEIV)
> 
> While that looks the same, it is semantically different. The first expression
> is true if CONFIG_NOP_USB_XCEIV is built as module and if the including
> code is built as module. The second expression is true if code depending on
> CONFIG_NOP_USB_XCEIV if built as module or into the kernel.
> 
> As a result, the arm:allmodconfig build fails with
> 
> arch/arm/mach-omap2/built-in.o: In function `omap3_evm_init':
> arch/arm/mach-omap2/board-omap3evm.c:703: undefined reference to
> 	`usb_nop_xceiv_register'
> 
> Fix the problem by reverting to the old conditional.
> 
> Cc: Josh Boyer <jwboyer@...hat.com>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>

I'm not entirely sure why I was CC'd on this one, but the patch looks
good to me.  I do wonder how many other uses of IS_ENABLED aren't taking
this into account though.

josh

> ---
>  include/linux/usb/usb_phy_gen_xceiv.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/usb/usb_phy_gen_xceiv.h b/include/linux/usb/usb_phy_gen_xceiv.h
> index f9a7e7b..11d85b9 100644
> --- a/include/linux/usb/usb_phy_gen_xceiv.h
> +++ b/include/linux/usb/usb_phy_gen_xceiv.h
> @@ -12,7 +12,7 @@ struct usb_phy_gen_xceiv_platform_data {
>  	unsigned int needs_reset:1;
>  };
>  
> -#if IS_ENABLED(CONFIG_NOP_USB_XCEIV)
> +#if defined(CONFIG_NOP_USB_XCEIV) || (defined(CONFIG_NOP_USB_XCEIV_MODULE) && defined(MODULE))
>  /* sometimes transceivers are accessed only through e.g. ULPI */
>  extern void usb_nop_xceiv_register(void);
>  extern void usb_nop_xceiv_unregister(void);
> -- 
> 1.7.9.7
> 
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