linux-kernel - Re: [PATCH] auxdisplay: ht16k33: select CONFIG_FB_SYS

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Date:   Fri, 25 Nov 2016 08:50:04 +0100
From:   Robin van der Gracht <robin@...tonic.nl>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Miguel Ojeda Sandonis <miguel.ojeda.sandonis@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] auxdisplay: ht16k33: select CONFIG_FB_SYS_FOPS

Hi Arnd,

On Wed, 23 Nov 2016 14:06:49 +0100
Arnd Bergmann <arnd@...db.de> wrote:

> The new driver caused a rare randconfig failure:
> 
> drivers/auxdisplay/ht16k33.o:(.data.ht16k33_fb_ops+0xc): undefined reference to `fb_sys_read'
> drivers/auxdisplay/ht16k33.o:(.data.ht16k33_fb_ops+0x10): undefined reference to `fb_sys_write'
> 
> This selects the respective helper module, like all other
> such drivers do.

Thanks for reporting this. You are right about the missing helper.
However, the fb_ops struct uses several helpers which are all missing.

static struct fb_ops ht16k33_fb_ops = {
	.owner = THIS_MODULE,
	.fb_read = fb_sys_read,
	.fb_write = fb_sys_write,
	.fb_fillrect = sys_fillrect,
	.fb_copyarea = sys_copyarea,
	.fb_imageblit = sys_imageblit,
	.fb_mmap = ht16k33_mmap,
};

HT16K33 should also select:
FB_CFB_FILLRECT
FB_CFB_COPYAREA
FB_CFB_IMAGEBLIT

> 
> Fixes: 8992da44c680 ("auxdisplay: ht16k33: Driver for LED controller")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/auxdisplay/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
> index a230ea797b92..b8bbfc64a1d1 100644
> --- a/drivers/auxdisplay/Kconfig
> +++ b/drivers/auxdisplay/Kconfig
> @@ -131,6 +131,7 @@ config IMG_ASCII_LCD
>  config HT16K33
>  	tristate "Holtek Ht16K33 LED controller with keyscan"
>  	depends on FB && OF && I2C && INPUT
> +	select FB_SYS_FOPS
>  	select INPUT_MATRIXKMAP
>  	select FB_BACKLIGHT
>  	help

Regards,
Robin