linux-kernel - Re: [v5 PATCH] RISC-V: Fix unsupported isa string info.

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Date:   Mon, 12 Aug 2019 08:02:15 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Atish Patra <atish.patra@....com>
Cc:     linux-kernel@...r.kernel.org, Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Johan Hovold <johan@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [v5 PATCH] RISC-V: Fix unsupported isa string info.

> +	for (e = mandatory_ext; *e != '\0'; ++e) {
> +		if (isa[0] != e[0]) {
> +#if defined(CONFIG_FP)
> +			if ((isa[0] == 'f') || (isa[0] == 'd'))
> +				continue;
> +#endif
> +			unsupported_isa[index] = e[0];
> +			index++;
> +		}

I'd just use if (IS_ENABLED()) here to get full compiler coverage.
Also no need for the inner braces.

> +	if (isa[0] != '\0') {
> +		/* Add remainging isa strings */
> +		for (e = isa; *e != '\0'; ++e) {
> +#if !defined(CONFIG_VIRTUALIZATION)
> +			if (e[0] != 'h')
> +#endif
> +				seq_write(f, e, 1);
> +		}
> +	}

This one I don't get.  Why do we want to check CONFIG_VIRTUALIZATION?

>  	seq_puts(f, "\n");
>  
>  	/*
>  	 * If we were given an unsupported ISA in the device tree then print
>  	 * a bit of info describing what went wrong.
>  	 */
> -	if (isa[0] != '\0')
> -		pr_info("unsupported ISA \"%s\" in device tree\n", orig_isa);
> +	if (unsupported_isa[0])
> +		pr_info("unsupported ISA extensions \"%s\" in device tree for cpu [%ld]\n",
> +			unsupported_isa, cpuid);

And I'm not even sure why we care about unsupported extensions.  Sooner
or late a few will op up and they should be harmless.