linux-kernel - Re: [PATCH] media: ti-vpe: cal: avoid FIELD

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Message-ID: <X81v22O9LxsAIUKs@pendragon.ideasonboard.com>
Date:   Mon, 7 Dec 2020 01:57:15 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Benoit Parrot <bparrot@...com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: ti-vpe: cal: avoid FIELD_GET assertion

Hi Arnd,

Thank you for the patch.

On Fri, Dec 04, 2020 at 12:07:30AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> FIELD_GET() must only be used with a mask that is a compile-time
> constant:
> 
> drivers/media/platform/ti-vpe/cal.h: In function 'cal_read_field':
> include/linux/compiler_types.h:320:38: error: call to '__compiletime_assert_247' declared with attribute error: FIELD_GET: mask is not constant
> include/linux/bitfield.h:46:3: note: in expansion of macro 'BUILD_BUG_ON_MSG'
>    46 |   BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),  \
>       |   ^~~~~~~~~~~~~~~~
> drivers/media/platform/ti-vpe/cal.h:220:9: note: in expansion of macro 'FIELD_GET'
>   220 |  return FIELD_GET(mask, cal_read(cal, offset));
>       |         ^~~~~~~~~
> 
> The problem here is that the function is not always inlined. Mark it
> __always_inline to avoid the problem.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

This doesn't conflict with the series I've just sent for the CAL driver,
and can thus be applied first or on top. Hans, can I let you handle this
?

> ---
>  drivers/media/platform/ti-vpe/cal.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/ti-vpe/cal.h b/drivers/media/platform/ti-vpe/cal.h
> index 4123405ee0cf..20d07311d222 100644
> --- a/drivers/media/platform/ti-vpe/cal.h
> +++ b/drivers/media/platform/ti-vpe/cal.h
> @@ -215,7 +215,7 @@ static inline void cal_write(struct cal_dev *cal, u32 offset, u32 val)
>  	iowrite32(val, cal->base + offset);
>  }
>  
> -static inline u32 cal_read_field(struct cal_dev *cal, u32 offset, u32 mask)
> +static __always_inline u32 cal_read_field(struct cal_dev *cal, u32 offset, u32 mask)
>  {
>  	return FIELD_GET(mask, cal_read(cal, offset));
>  }

-- 
Regards,

Laurent Pinchart