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Date:   Mon, 5 Nov 2018 22:56:49 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Nick Kossifidis <mick@ics.forth.gr>
Cc:     Vincent Chen <vincentc@andestech.com>, aou@eecs.berkeley.edu,
        arnd@arndb.de, alankao@andestech.com, greentime@andestech.com,
        palmer@sifive.com, linux-kernel@vger.kernel.org,
        zong@andestech.com, linux-riscv@lists.infradead.org,
        deanbo422@gmail.com
Subject: Re: [RFC 0/2] RISC-V: A proposal to add vendor-specific code
Message-ID: <20181106065649.GA13526@infradead.org>
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On Mon, Nov 05, 2018 at 09:39:29PM +0200, Nick Kossifidis wrote:
> a) By directly modifying your custom CSRs, it means that we will need
> compiler support in order to compile a kernel with your code in it. This
> will break CI systems and will introduce various issues on testing and
> reviewing your code. In general if we need custom toolchains to compile
> the kernel, that may be unavailable (vendors will not always open source
> their compiler support), we won't be able to maintain a decent level of
> code quality in the tree. How can the maintainer push your code on the
> repository if he/she can't even perform a basic compilation test ?

And that (besides avoiding the wild growth of extensions) is the major
reason why accepting vendor specific CSRs or instructions is a no-go.