linux-kernel - Re: [PATCH v2] xen kconfig: don't "select INPUT_XEN_KBDDEV

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Date:	Tue, 16 Feb 2016 16:55:42 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Andrew Jones <drjones@...hat.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	<linux-fbdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xensource.com>, <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH v2] xen kconfig: don't "select
 INPUT_XEN_KBDDEV_FRONTEND"

On Tue, 16 Feb 2016, Arnd Bergmann wrote:
> The Xen framebuffer driver selects the xen keyboard driver, so the latter
> will be built-in if XEN_FBDEV_FRONTEND=y. However, when CONFIG_INPUT
> is a loadable module, this configuration cannot work. On mainline kernels,
> the symbol will be enabled but not used, while in combination with
> a patch I have to detect such useless configurations, we get the
> expected link failure:
> 
> drivers/input/built-in.o: In function `xenkbd_remove':
> xen-kbdfront.c:(.text+0x2f0): undefined reference to `input_unregister_device'
> xen-kbdfront.c:(.text+0x30e): undefined reference to `input_unregister_device'
> 
> This removes the extra "select", as it just causes more trouble than
> it helps. In theory, some defconfig file might break if it has
> XEN_FBDEV_FRONTEND in it but not INPUT_XEN_KBDDEV_FRONTEND. The Kconfig
> fragment we ship in the kernel (kernel/configs/xen.config) however
> already enables both, and anyone using an old .config file would
> keep having both enabled.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> Suggested-by: David Vrabel <david.vrabel@...rix.com>
> Fixes: 36c1132e34bd ("xen kconfig: fix select INPUT_XEN_KBDDEV_FRONTEND")

Acked-by: Stefano Stabellini <stefano.stabellini@...citrix.com>


> diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
> index 8ea45a5cd806..d889ef2048df 100644
> --- a/drivers/video/fbdev/Kconfig
> +++ b/drivers/video/fbdev/Kconfig
> @@ -2246,7 +2246,6 @@ config XEN_FBDEV_FRONTEND
>  	select FB_SYS_IMAGEBLIT
>  	select FB_SYS_FOPS
>  	select FB_DEFERRED_IO
> -	select INPUT_XEN_KBDDEV_FRONTEND if INPUT_MISC
>  	select XEN_XENBUS_FRONTEND
>  	default y
>  	help
>