Re: [Linux-kernel-mentees] [PATCH v3] video: atmel_lcdc: Fix Shifting signed 32 bit value by 31 bits problem

From: <Nicolas.Ferre@microchip.com>
To: <shobhitkukreti@gmail.com>, <b.zolnierkie@samsung.com>,
	<sam@ravnborg.org>
Cc: alexandre.belloni@bootlin.com,
	linux-kernel-mentees@lists.linuxfoundation.org,
	Ludovic.Desroches@microchip.com
Subject: Re: [Linux-kernel-mentees] [PATCH v3] video: atmel_lcdc: Fix Shifting signed 32 bit value by 31 bits problem
Date: Wed, 8 Jan 2020 13:08:26 +0000	[thread overview]
Message-ID: <16eb49b4-6035-1b52-4dce-faec2c0fbf9f@microchip.com> (raw)
In-Reply-To: <1563756160-29702-1-git-send-email-shobhitkukreti@gmail.com>

On 22/07/2019 at 02:42, Shobhit Kukreti wrote:
> Fix ATMEL_LCDC_MEMOR and ATMEL_LCDC_MEMOR_LITTLE defines to use "U"
> cast to avoid shifting signed 32 bit values by 31 bit problem. This
> problem. This is not a problem for gcc built kernel.

Chuck of a sentence remaining.

> However, this may be a problem since the header is part of pbulic API

Typo
+
no, this header is not part of public API.

> which could be included for builds using compilers which do not handle
> this condition safely resulting in undefined behavior
> 
> Signed-off-by: Shobhit Kukreti <shobhitkukreti@gmail.com>

No strong opinion, but once typo and commit message is fixed, you can 
add my:
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>

Regards,
    Nicolas

> ---
> Changes in v3:
> 	Replace Bit Shift Operations with BIT() macros
> 
> Changes in v2:
>         Fixed spelling typo
> 
>   include/video/atmel_lcdc.h | 28 ++++++++++++++--------------
>   1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/include/video/atmel_lcdc.h b/include/video/atmel_lcdc.h
> index 43e497c..985e2d6 100644
> --- a/include/video/atmel_lcdc.h
> +++ b/include/video/atmel_lcdc.h
> @@ -85,27 +85,27 @@ struct atmel_lcdfb_pdata {
>   #define		ATMEL_LCDC_PIXELSIZE_16		(4 << 5)
>   #define		ATMEL_LCDC_PIXELSIZE_24		(5 << 5)
>   #define		ATMEL_LCDC_PIXELSIZE_32		(6 << 5)
> -#define	ATMEL_LCDC_INVVD	(1 << 8)
> +#define	ATMEL_LCDC_INVVD	BIT(8)
>   #define		ATMEL_LCDC_INVVD_NORMAL		(0 << 8)
> -#define		ATMEL_LCDC_INVVD_INVERTED	(1 << 8)
> -#define	ATMEL_LCDC_INVFRAME	(1 << 9 )
> +#define		ATMEL_LCDC_INVVD_INVERTED	BIT(8)
> +#define	ATMEL_LCDC_INVFRAME	BIT(9)
>   #define		ATMEL_LCDC_INVFRAME_NORMAL	(0 << 9)
> -#define		ATMEL_LCDC_INVFRAME_INVERTED	(1 << 9)
> -#define	ATMEL_LCDC_INVLINE	(1 << 10)
> +#define		ATMEL_LCDC_INVFRAME_INVERTED	BIT(9)
> +#define	ATMEL_LCDC_INVLINE	BIT(10)
>   #define		ATMEL_LCDC_INVLINE_NORMAL	(0 << 10)
> -#define		ATMEL_LCDC_INVLINE_INVERTED	(1 << 10)
> -#define	ATMEL_LCDC_INVCLK	(1 << 11)
> +#define		ATMEL_LCDC_INVLINE_INVERTED	BIT(10)
> +#define	ATMEL_LCDC_INVCLK	BIT(11)
>   #define		ATMEL_LCDC_INVCLK_NORMAL	(0 << 11)
> -#define		ATMEL_LCDC_INVCLK_INVERTED	(1 << 11)
> -#define	ATMEL_LCDC_INVDVAL	(1 << 12)
> +#define		ATMEL_LCDC_INVCLK_INVERTED	BIT(11)
> +#define	ATMEL_LCDC_INVDVAL	BIT(12)
>   #define		ATMEL_LCDC_INVDVAL_NORMAL	(0 << 12)
> -#define		ATMEL_LCDC_INVDVAL_INVERTED	(1 << 12)
> -#define	ATMEL_LCDC_CLKMOD	(1 << 15)
> +#define		ATMEL_LCDC_INVDVAL_INVERTED	BIT(12)
> +#define	ATMEL_LCDC_CLKMOD	BIT(15)
>   #define		ATMEL_LCDC_CLKMOD_ACTIVEDISPLAY	(0 << 15)
> -#define		ATMEL_LCDC_CLKMOD_ALWAYSACTIVE	(1 << 15)
> -#define	ATMEL_LCDC_MEMOR	(1 << 31)
> +#define		ATMEL_LCDC_CLKMOD_ALWAYSACTIVE	BIT(15)
> +#define	ATMEL_LCDC_MEMOR	BIT(31)
>   #define		ATMEL_LCDC_MEMOR_BIG		(0 << 31)
> -#define		ATMEL_LCDC_MEMOR_LITTLE		(1 << 31)
> +#define		ATMEL_LCDC_MEMOR_LITTLE		BIT(31)
>   
>   #define ATMEL_LCDC_TIM1		0x0808
>   #define	ATMEL_LCDC_VFP		(0xffU <<  0)
> 

-- 
Nicolas Ferre
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