linux-kernel - Re: [PATCH v5 3/5] efi/cper: Add a new helper function to print bitmasks

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Message-ID: <20250814171334.00002f29@huawei.com>
Date: Thu, 14 Aug 2025 17:13:34 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Daniel Ferguson <danielf@...amperecomputing.com>
CC: Ard Biesheuvel <ardb@...nel.org>, Jonathan Corbet <corbet@....net>,
	"Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>, "James
 Morse" <james.morse@....com>, Tony Luck <tony.luck@...el.com>, "Borislav
 Petkov" <bp@...en8.de>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-efi@...r.kernel.org>, <linux-edac@...r.kernel.org>, "Mauro Carvalho
 Chehab" <mchehab+huawei@...nel.org>
Subject: Re: [PATCH v5 3/5] efi/cper: Add a new helper function to print
 bitmasks

On Wed, 13 Aug 2025 14:19:16 -0700
Daniel Ferguson <danielf@...amperecomputing.com> wrote:

> From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> 
> Add a helper function to print a string with names associated
> to each bit field.
> 
> A typical example is:
> 
> 	const char * const bits[] = {
> 		"bit 3 name",
> 		"bit 4 name",
> 		"bit 5 name",
> 	};
> 	char str[120];
>         unsigned int bitmask = BIT(3) | BIT(5);
> 
> 	#define MASK  GENMASK(5,3)
> 
> 	cper_bits_to_str(str, sizeof(str), FIELD_GET(MASK, bitmask),
> 			 bits, ARRAY_SIZE(bits));
> 
> The above code fills string "str" with "bit 3 name|bit 5 name".
> 
> Reviewed-by; Jonathan Cameron <Jonathan.Cameron@...wei.com>
My typo still here :(

So drop that garbage and

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>


> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
> ---
>  drivers/firmware/efi/cper.c | 60 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/cper.h        |  2 ++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c
> index 928409199a1a4009b11cf3189fe036ad8861169c..79ba688a64f8da7af2dad097b9331c72afc73864 100644
> --- a/drivers/firmware/efi/cper.c
> +++ b/drivers/firmware/efi/cper.c
> @@ -12,6 +12,7 @@
>   * Specification version 2.4.
>   */
>  
> +#include <linux/bitmap.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/time.h>
> @@ -106,6 +107,65 @@ void cper_print_bits(const char *pfx, unsigned int bits,
>  		printk("%s\n", buf);
>  }
>  
> +/**
> + * cper_bits_to_str - return a string for set bits
> + * @buf: buffer to store the output string
> + * @buf_size: size of the output string buffer
> + * @bits: bit mask
> + * @strs: string array, indexed by bit position
> + * @strs_size: size of the string array: @strs
> + *
> + * Add to @buf the bitmask in hexadecimal. Then, for each set bit in @bits,
> + * add the corresponding string describing the bit in @strs to @buf.
> + *
> + * A typical example is::
> + *
> + *	const char * const bits[] = {
> + *		"bit 3 name",
> + *		"bit 4 name",
> + *		"bit 5 name",
> + *	};
> + *	char str[120];
> + *	unsigned int bitmask = BIT(3) | BIT(5);
> + *	#define MASK GENMASK(5,3)
> + *
> + *	cper_bits_to_str(str, sizeof(str), FIELD_GET(MASK, bitmask),
> + *			 bits, ARRAY_SIZE(bits));
> + *
> + * The above code fills the string ``str`` with ``bit 3 name|bit 5 name``.
> + *
> + * Return: number of bytes stored or an error code if lower than zero.
> + */
> +int cper_bits_to_str(char *buf, int buf_size, unsigned long bits,
> +		     const char * const strs[], unsigned int strs_size)
> +{
> +	int len = buf_size;
> +	char *str = buf;
> +	int i, size;
> +
> +	*buf = '\0';
> +
> +	for_each_set_bit(i, &bits, strs_size) {
> +		if (!(bits & BIT_ULL(i)))
> +			continue;
> +
> +		if (*buf && len > 0) {
> +			*str = '|';
> +			len--;
> +			str++;
> +		}
> +
> +		size = strscpy(str, strs[i], len);
> +		if (size < 0)
> +			return size;
> +
> +		len -= size;
> +		str += size;
> +	}
> +	return len - buf_size;
> +}
> +EXPORT_SYMBOL_GPL(cper_bits_to_str);
> +
>  static const char * const proc_type_strs[] = {
>  	"IA32/X64",
>  	"IA64",
> diff --git a/include/linux/cper.h b/include/linux/cper.h
> index 0ed60a91eca9d6425c9a41947a927b59f7aa2c71..58f40477c824e61c7f798978947bf1f441ce45ad 100644
> --- a/include/linux/cper.h
> +++ b/include/linux/cper.h
> @@ -588,6 +588,8 @@ const char *cper_mem_err_type_str(unsigned int);
>  const char *cper_mem_err_status_str(u64 status);
>  void cper_print_bits(const char *prefix, unsigned int bits,
>  		     const char * const strs[], unsigned int strs_size);
> +int cper_bits_to_str(char *buf, int buf_size, unsigned long bits,
> +		     const char * const strs[], unsigned int strs_size);
>  void cper_mem_err_pack(const struct cper_sec_mem_err *,
>  		       struct cper_mem_err_compact *);
>  const char *cper_mem_err_unpack(struct trace_seq *,
>