linux-kernel - Re: [PATCH v2 1/3] RISC-V: Add separate asm/encoding.h for spec related defines

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Date:   Mon, 15 Apr 2019 12:59:31 +0530
From:   Anup Patel <anup@...infault.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Anup Patel <Anup.Patel@....com>, Albert Ou <aou@...s.berkeley.edu>,
        Palmer Dabbelt <palmer@...ive.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Atish Patra <Atish.Patra@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH v2 1/3] RISC-V: Add separate asm/encoding.h for spec
 related defines

On Mon, Apr 15, 2019 at 11:19 AM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Sat, Apr 13, 2019 at 03:38:35PM +0000, Anup Patel wrote:
> > It's better to have all RISC-V spec related defines in one place
> > so this patch adds separate asm/encoding.h for such defines which
> > can be included in assembly as well as C code.
>
> As per the discussion of version 1 on Saturday I disagree with this
> move.  There is both a philosophical and a practical reason for that:
>
>  a) in RISC-V CSR access is really nicely split out into a separate
>     number space, just accessed through a few special instructions.
>     It has no overlap with the rest of instruction encoding
>  b) <asm/csr.h> is pulled into just about every file build in the kernel
>     though <asm/irqflags.h>, <asm/switch_to.h> and <asm/thread_info.h>
>
> So even if you want to later add a new <asm/encoding.h> for instruction
> encoding details later, I'd rather prefer to keep CSR access separate
> from it.

Sure, no problem. I will add asm/encoding.h for instructions later.

Regards,
Anup