Re: [PATCH] ARM: ptrace: Use bitfield helpers
From: Russell King (Oracle)
Date: Mon Nov 22 2021 - 11:18:11 EST
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.
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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