linux-kernel - Re: [PATCH v2] video: radeon.h Fix Shifting signed 32 bit value by 31 bits problem

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Message-ID: <85b130de-4e1b-3004-ae5a-3cda5d732bcb@samsung.com>
Date:   Mon, 19 Aug 2019 16:33:59 +0200
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Shobhit Kukreti <shobhitkukreti@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v2] video: radeon.h Fix Shifting signed 32 bit value by
 31 bits problem


Hi,

On 7/22/19 3:14 AM, Shobhit Kukreti wrote:
> Fix RB2D_DC_BUSY and HORZ_AUTO_RATIO_INC defines to use "U" cast to
> avoid shifting signed 32 bit values by 31 bit problem. This is not a
> problem for gcc built kernel.
> 
> However, the header file being a public api, other compilers may not
> handle the condition safely resulting in undefined behavior.
> 
> Signed-off-by: Shobhit Kukreti <shobhitkukreti@...il.com>
> ---
> Changes in v2:
> 	Replace bit shift operations with BIT() macro

1. Please update the patch summary & description to reflect that,
please see commit 13990cf8a180 for the reference:

commit 13990cf8a180cc070f0b1266140e799db8754289
Author: Amol Surati <suratiamol@...il.com>
Date:   Sun Jul 7 14:27:29 2019 +0530

    ide: use BIT() macro for defining bit-flags
    
    The BIT() macro is available for defining the required bit-flags.
    
    Since it operates on an unsigned value and expands to an unsigned result,
    using it, instead of an expression like (1 << x), also fixes the problem
    of shifting a signed 32-bit value by 31 bits (e.g. 1 << 31).
    
    Signed-off-by: Amol Surati <suratiamol@...il.com>
    Signed-off-by: David S. Miller <davem@...emloft.net>


2. Please use ./scripts/checkpatch.pl to check your patch and fix issue
reported by the script:

WARNING: please, no space before tabs
#147: FILE: include/video/radeon.h:458:
+#define FORCEON_MCLKB         ^I^I   ^I   BIT(17)$

WARNING: please, no space before tabs
#148: FILE: include/video/radeon.h:459:
+#define FORCEON_YCLKA         ^I    ^I   ^I   BIT(18)$

WARNING: please, no space before tabs
#149: FILE: include/video/radeon.h:460:
+#define FORCEON_YCLKB         ^I^I   ^I   BIT(19)$

WARNING: please, no space before tabs
#150: FILE: include/video/radeon.h:461:
+#define FORCEON_MC            ^I^I   ^I   BIT(20)$

WARNING: please, no space before tabs
#151: FILE: include/video/radeon.h:462:
+#define FORCEON_AIC           ^I^I   ^I   BIT(21)$

WARNING: please, no space before tabs
#219: FILE: include/video/radeon.h:544:
+#define CRTC_BYPASS_LUT_EN     ^I^I^I   BIT(14)$

WARNING: please, no space before tabs
#220: FILE: include/video/radeon.h:545:
+#define CRTC_EXT_DISP_EN      ^I^I^I   BIT(24)$

WARNING: please, no space before tabs
#453: FILE: include/video/radeon.h:740:
+#define SOFT_RESET_CP           ^I^I   BIT(0)$

WARNING: please, no space before tabs
#454: FILE: include/video/radeon.h:741:
+#define SOFT_RESET_HI           ^I^I   BIT(1)$

WARNING: please, no space before tabs
#455: FILE: include/video/radeon.h:742:
+#define SOFT_RESET_SE           ^I^I   BIT(2)$

WARNING: please, no space before tabs
#456: FILE: include/video/radeon.h:743:
+#define SOFT_RESET_RE           ^I^I   BIT(3)$

WARNING: please, no space before tabs
#457: FILE: include/video/radeon.h:744:
+#define SOFT_RESET_PP           ^I^I   BIT(4)$

WARNING: please, no space before tabs
#458: FILE: include/video/radeon.h:745:
+#define SOFT_RESET_E2           ^I^I   BIT(5)$

WARNING: please, no space before tabs
#459: FILE: include/video/radeon.h:746:
+#define SOFT_RESET_RB           ^I^I   BIT(6)$

WARNING: please, no space before tabs
#460: FILE: include/video/radeon.h:747:
+#define SOFT_RESET_HDP          ^I^I   BIT(7)$

WARNING: please, no space before tabs
#496: FILE: include/video/radeon.h:888:
+#define GMC_CLR_CMP_CNTL_DIS      ^I^I   BIT(28)$

total: 0 errors, 17 warnings, 0 checks, 502 lines checked


3. Please update Cc: list of your mail by all mailing lists returned by
./scripts/get_maintainer.pl:

$ ./scripts/get_maintainer.pl -f include/video/atmel_lcdc.h
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com> (maintainer:FRAMEBUFFER LAYER)
dri-devel@...ts.freedesktop.org (open list:FRAMEBUFFER LAYER)
linux-fbdev@...r.kernel.org (open list:FRAMEBUFFER LAYER)
linux-kernel@...r.kernel.org (open list)

>  include/video/radeon.h | 338 ++++++++++++++++++++++++-------------------------
>  1 file changed, 169 insertions(+), 169 deletions(-)
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics