linux-kernel - Re: [PATCH v2 01/28] lib/printbuf: New data structure for printing strings

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Message-ID: <Yo+XZ4YtU9fN/sGE@alley>
Date:   Thu, 26 May 2022 17:06:15 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Kent Overstreet <kent.overstreet@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
        rostedt@...dmis.org, senozhatsky@...omium.org,
        andriy.shevchenko@...ux.intel.com, willy@...radead.org
Subject: Re: [PATCH v2 01/28] lib/printbuf: New data structure for printing
 strings

On Thu 2022-05-19 13:23:54, Kent Overstreet wrote:
> This adds printbufs: a printbuf points to a char * buffer and knows the
> size of the output buffer as well as the current output position.
> 
> Future patches will be adding more features to printbuf, but initially
> printbufs are targeted at refactoring and improving our existing code in
> lib/vsprintf.c - so this initial printbuf patch has the features
> required for that.

> diff --git a/include/linux/printbuf.h b/include/linux/printbuf.h
> new file mode 100644
> index 0000000000..40dc07040d
> --- /dev/null
> +++ b/include/linux/printbuf.h
> +static inline void pr_chars(struct printbuf *out, char c, unsigned n)
> +{
> +	memset(out->buf + out->pos,
> +	       c,
> +	       min(n, printbuf_remaining(out)));
> +	out->pos += n;
> +	printbuf_nul_terminate(out);
> +}

This function is not later used. Please, do not add API
that will not have users in the same patchset.

There are several other cases. I am not going to comment
all of them.


> +static inline void __pr_char(struct printbuf *out, char c)
> +{
> +	if (printbuf_remaining(out))
> +		out->buf[out->pos] = c;
> +	out->pos++;
> +}
> +
> +static inline void pr_char(struct printbuf *out, char c)
> +{
> +	__pr_char(out, c);
> +	printbuf_nul_terminate(out);
> +}

The "pr_" prefix is a nightmare for me because the same prefix
is used also for printk() API ;-)

Could we please use "pb_" instead?

Note that "prb_" prefix is already used by the lockless printk
ringbuffer, see kernel/printk/printk_ringbuffer.h.

Best Regards,
Petr