Date:   Mon, 22 Nov 2021 16:17:56 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Geert Uytterhoeven <geert+renesas@glider.be>
Cc:     Oleg Nesterov <oleg@redhat.com>,
        Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ARM: ptrace: Use bitfield helpers
Message-ID: <YZvCtN/WNyogs9JZ@shell.armlinux.org.uk>
References: <a1445d3abb45cfc95cb1b03180fd53caf122035b.1637593297.git.geert+renesas@glider.be>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>
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On Mon, Nov 22, 2021 at 04:53:41PM +0100, Geert Uytterhoeven wrote:
> The isa_mode() macro extracts two fields, and recombines them into a
> single value.  The shift value of the J-bit may look off-by-one to the
> casual reader, as it is the net result of the extraction and
> recombination steps.

I'd recommend avoiding the suggestion that the explicit "- 1" could
be misinterpreted as an off-by-one error.

>  #define isa_mode(regs) \
> -	((((regs)->ARM_cpsr & PSR_J_BIT) >> (__ffs(PSR_J_BIT) - 1)) | \
> -	 (((regs)->ARM_cpsr & PSR_T_BIT) >> (__ffs(PSR_T_BIT))))
> +	((FIELD_GET(PSR_J_BIT, (regs)->ARM_cpsr) << 1) | \

I'd suggest getting rid of the extra unnecessary parens there.
Too many parens leads to a decrease in readability.

-- 
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