Re: [PATCH v4 02/28] printk: Add print format (%pra) for struct range

[Fan Ni <nifan.cxl@gmail.com>]

On Mon, Oct 07, 2024 at 06:16:08PM -0500, Ira Weiny wrote:
> The use of struct range in the CXL subsystem is growing.  In particular,
> the addition of Dynamic Capacity devices uses struct range in a number
> of places which are reported in debug and error messages.
> 
> To wit requiring the printing of the start/end fields in each print
> became cumbersome.  Dan Williams mentions in [1] that it might be time
> to have a print specifier for struct range similar to struct resource
> 
> A few alternatives were considered including '%par', '%r', and '%pn'.
> %pra follows that struct range is similar to struct resource (%p[rR])
> but need to be different.  Based on discussions with Petr and Andy
> '%pra' was chosen.[2]
> 
> Andy also suggested to keep the range prints similar to struct resource
> though combined code.  Add hex_range() to handle printing for both
> pointer types.
> 
> To: Petr Mladek <pmladek@suse.com>
> To: Steven Rostedt <rostedt@goodmis.org>
> To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
> To: Sergey Senozhatsky <senozhatsky@chromium.org>
> To: Jonathan Corbet <corbet@lwn.net> (maintainer:DOCUMENTATION)
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org (open list)
> Link: https://lore.kernel.org/all/663922b475e50_d54d72945b@dwillia2-xfh.jf.intel.com.notmuch/ [1]
> Link: https://lore.kernel.org/all/66cea3bf3332f_f937b29424@iweiny-mobl.notmuch/ [2]
> Suggested-by: "Dan Williams" <dan.j.williams@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> 
> ---
> Changes:
> [Andy: create new hex_range() and use it in both range/resource]
> [Petr/Andy: Use %pra]
> [Andy: Add test case start > end]
> [Petr: Update documentation]
> [Petr: use 'range -']
> [Petr: fixup printf_spec specifiers]
> [Petr: add lib/test_printf test]
> ---
>  Documentation/core-api/printk-formats.rst | 13 ++++++++
>  lib/test_printf.c                         | 26 +++++++++++++++
>  lib/vsprintf.c                            | 55 +++++++++++++++++++++++++++----
>  3 files changed, 88 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
> index 14e093da3ccd..03b102fc60bb 100644
> --- a/Documentation/core-api/printk-formats.rst
> +++ b/Documentation/core-api/printk-formats.rst
> @@ -231,6 +231,19 @@ width of the CPU data path.
>  
>  Passed by reference.
>  
> +Struct Range
> +------------
> +
> +::
> +
> +	%pra    [range 0x0000000060000000-0x000000006fffffff]
> +	%pra    [range 0x0000000060000000]
> +
> +For printing struct range.  struct range holds an arbitrary range of u64
> +values.  If start is equal to end only 1 value is printed.
> +
> +Passed by reference.
> +
>  DMA address types dma_addr_t
>  ----------------------------
>  
> diff --git a/lib/test_printf.c b/lib/test_printf.c
> index 5afdf5efc627..e3e75b6d10a0 100644
> --- a/lib/test_printf.c
> +++ b/lib/test_printf.c
> @@ -432,6 +432,31 @@ struct_resource(void)
>  	     "%pR", &test_resource);
>  }
>  
> +static void __init
> +struct_range(void)
> +{
> +	struct range test_range = {
> +		.start = 0xc0ffee00ba5eba11,
> +		.end = 0xc0ffee00ba5eba11,
> +	};
> +
> +	test("[range 0xc0ffee00ba5eba11]", "%pra", &test_range);
> +
> +	test_range = (struct range) {
> +		.start = 0xc0ffee,
> +		.end = 0xba5eba11,
> +	};
> +	test("[range 0x0000000000c0ffee-0x00000000ba5eba11]",
> +	     "%pra", &test_range);
> +
> +	test_range = (struct range) {
> +		.start = 0xba5eba11,
> +		.end = 0xc0ffee,
> +	};
> +	test("[range 0x00000000ba5eba11-0x0000000000c0ffee]",
> +	     "%pra", &test_range);
> +}
> +
 ...
>  static noinline_for_stack
>  char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
>  		 const char *fmt)
> @@ -2277,6 +2314,7 @@ char *rust_fmt_argument(char *buf, char *end, void *ptr);
>   * - 'Bb' as above with module build ID (for use in backtraces)
>   * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref]
>   * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
> + * - 'ra' struct ranges [range 0x00 - 0xff]

Maybe follow the existing examples here, like
'ra" For struct ranges, e.g., ...

fan

>   * - 'b[l]' For a bitmap, the number of bits is determined by the field
>   *       width which must be explicitly specified either as part of the
>   *       format string '%32b[l]' or through '%*b[l]', [l] selects
> @@ -2399,8 +2437,13 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
>  		fallthrough;
>  	case 'B':
>  		return symbol_string(buf, end, ptr, spec, fmt);
> -	case 'R':
>  	case 'r':
> +		switch (fmt[1]) {
> +		case 'a':
> +			return range_string(buf, end, ptr, spec, fmt);
> +		}
> +		fallthrough;
> +	case 'R':
>  		return resource_string(buf, end, ptr, spec, fmt);
>  	case 'h':
>  		return hex_string(buf, end, ptr, spec, fmt);
> 
> -- 
> 2.46.0
> 

-- 
Fan Ni