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Date:   Mon, 01 May 2023 07:52:37 -0700 (PDT)
Subject:     Re: [PATCH 1/4] RISC-V: create ISA string separately - not as part of cpuinfo
In-Reply-To: <20230424194911.264850-2-heiko.stuebner@vrull.eu>
CC:     linux-riscv@lists.infradead.org,
        Paul Walmsley <paul.walmsley@sifive.com>, heiko@sntech.de,
        kito.cheng@sifive.com, jrtc27@jrtc27.com,
        Conor Dooley <conor.dooley@microchip.com>,
        matthias.bgg@gmail.com, heinrich.schuchardt@canonical.com,
        greentime.hu@sifive.com, nick.knight@sifive.com,
        christoph.muellner@vrull.eu, philipp.tomsich@vrull.eu,
        Richard Henderson <richard.henderson@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>, linux-kernel@vger.kernel.org,
        heiko.stuebner@vrull.eu
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     heiko@sntech.de
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On Mon, 24 Apr 2023 12:49:08 PDT (-0700), heiko@sntech.de wrote:
> From: Heiko Stuebner <heiko.stuebner@vrull.eu>
>
> The isa string is a very central part of the RISC-V architecture, so will
> be needed in other places as well.
>
> So in a first step decouple the generation of the runtime isa-string from
> /proc/cpuinfo - its current only user.

I'm also going to leave this one out, both because it fails to build and 
because the proposed second user isn't going to fly.  I'm not opposed to 
the refactoring, but too late for this merge window.

> The resulting string should not differ from the previously generated one.
>
> Signed-off-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> ---
>  arch/riscv/kernel/cpu.c | 70 ++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 62 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index 3df38052dcbd..ebc478f0a16c 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -193,10 +193,33 @@ static struct riscv_isa_ext_data isa_ext_arr[] = {
>  	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
>  };
>
> -static void print_isa_ext(struct seq_file *f)
> +static int strlen_isa_ext(void)
>  {
>  	struct riscv_isa_ext_data *edata;
> -	int i = 0, arr_sz;
> +	int ext_len = 0, i, arr_sz;
> +
> +	arr_sz = ARRAY_SIZE(isa_ext_arr) - 1;
> +
> +	/* No extension support available */
> +	if (arr_sz <= 0)
> +		return 0;
> +
> +	for (i = 0; i <= arr_sz; i++) {
> +		edata = &isa_ext_arr[i];
> +		if (!__riscv_isa_extension_available(NULL, edata->isa_ext_id))
> +			continue;
> +
> +		/* string length + underscore */
> +		ext_len += strlen(edata->uprop) + 1;
> +	}
> +
> +	return ext_len;
> +}
> +
> +static void strcat_isa_ext(char *isa_str)
> +{
> +	struct riscv_isa_ext_data *edata;
> +	int i, arr_sz;
>
>  	arr_sz = ARRAY_SIZE(isa_ext_arr) - 1;
>
> @@ -208,7 +231,8 @@ static void print_isa_ext(struct seq_file *f)
>  		edata = &isa_ext_arr[i];
>  		if (!__riscv_isa_extension_available(NULL, edata->isa_ext_id))
>  			continue;
> -		seq_printf(f, "_%s", edata->uprop);
> +		strcat(isa_str, "_");
> +		strcat(isa_str, edata->uprop);
>  	}
>  }
>
> @@ -220,19 +244,49 @@ static void print_isa_ext(struct seq_file *f)
>   */
>  static const char base_riscv_exts[13] = "imafdqcbkjpvh";
>
> -static void print_isa(struct seq_file *f, const char *isa)
> +static char *riscv_create_isa_string(const char *isa)
>  {
> +	int maxlen = 4;
> +	char *isa_str;
>  	int i;
>
> -	seq_puts(f, "isa\t\t: ");
> +	/* calculate the needed string length */
> +	for (i = 0; i < sizeof(base_riscv_exts); i++)
> +		if (__riscv_isa_extension_available(NULL, base_riscv_exts[i] - 'a'))
> +			maxlen++;
> +	maxlen += strlen_isa_ext();
> +
> +	isa_str = kzalloc(maxlen, GFP_KERNEL);
> +	if (!isa_str)
> +		return ERR_PTR(-ENOMEM);
> +
>  	/* Print the rv[64/32] part */
> -	seq_write(f, isa, 4);
> +	strncat(isa_str, isa, 4);
> +
>  	for (i = 0; i < sizeof(base_riscv_exts); i++) {
>  		if (__riscv_isa_extension_available(NULL, base_riscv_exts[i] - 'a'))
>  			/* Print only enabled the base ISA extensions */
> -			seq_write(f, &base_riscv_exts[i], 1);
> +			strncat(isa_str, &base_riscv_exts[i], 1);
> +	}
> +
> +	strcat_isa_ext(isa_str);
> +
> +	return isa_str;
> +}
> +
> +static void print_isa(struct seq_file *f, const char *isa)
> +{
> +	char *isa_str;
> +
> +	seq_puts(f, "isa\t\t: ");
> +
> +	isa_str = riscv_create_isa_string(isa);
> +	if (!IS_ERR(isa_str)) {
> +		seq_write(f, isa_str, strlen(isa_str));
> +		kfree(isa_str);
> +	} else {
> +		seq_puts(f, "unknown");
>  	}
> -	print_isa_ext(f);
>  	seq_puts(f, "\n");
>  }