linux-kernel - Re: [PATCH v2 3/5] efi/cper: Add a new helper function to print bitmasks

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Message-ID: <20240902112429.GEZtWgbSo0EVe0EyWE@fat_crate.local>
Date: Mon, 2 Sep 2024 13:24:29 +0200
From: Borislav Petkov <bp@...en8.de>
To: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc: Tony Luck <tony.luck@...el.com>, Ard Biesheuvel <ardb@...nel.org>,
	James Morse <james.morse@....com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Len Brown <lenb@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Shiju Jose <shiju.jose@...wei.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Dave Jiang <dave.jiang@...el.com>, Ira Weiny <ira.weiny@...el.com>,
	linux-acpi@...r.kernel.org, linux-edac@...r.kernel.org,
	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] efi/cper: Add a new helper function to print
 bitmasks

On Thu, Jul 11, 2024 at 08:28:54AM +0200, Mauro Carvalho Chehab wrote:
> Sometimes it is desired to produce a single log line for errors.
> Add a new helper function for such purpose.

How does this have anything to do with the below function?

Example?

Why isn't anything in lib/bitmap-str.c not useful for this?

> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> ---
>  drivers/firmware/efi/cper.c | 43 +++++++++++++++++++++++++++++++++++++
>  include/linux/cper.h        |  2 ++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c
> index 7d2cdd9e2227..462d739e8dd1 100644
> --- a/drivers/firmware/efi/cper.c
> +++ b/drivers/firmware/efi/cper.c
> @@ -106,6 +106,49 @@ 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. 

Where does it do that?

> Then, for each set bit in @bits,
> + * add the corresponding string describing the bit in @strs to @buf.
> + *
> + * 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 & (1U << (i))))

BIT_UL()

> +			continue;
> +
> +		if (*buf && len > 0) {

Uff, this is testing the first char in buf and it gets copied in below in
strscpy() through the str pointer.

So this function converts a set of set bits to their corresponding *names*
from strs[].

This name doesn't even begin to explain what this function does - it converts
a bitmap to the corresponding names of the bits in @strs. If anything, the
above comment needs an example and the function needs to be named properly.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette