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 needs 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.

Finally introduce DEFINE_RANGE() as a parallel to DEFINE_RES_*() and use
it in the tests.

Cc: 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: s/resource_and_range/resource_or_range/]
---
 Documentation/core-api/printk-formats.rst | 13 +++++++
 include/linux/range.h                     |  6 ++++
 lib/test_printf.c                         | 17 +++++++++
 lib/vsprintf.c                            | 57 +++++++++++++++++++++++++++----
 4 files changed, 87 insertions(+), 6 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 552f51046cf3..ecccc0473da9 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -236,6 +236,19 @@ width of the CPU data path.
 
 Passed by reference.
 
+Struct Range
+------------
+
+::
+
+	%pra    [range 0x0000000060000000-0x000000006fffffff] or
+		[range 0x0000000060000000]
+
+For printing struct range.  struct range holds an arbitrary range of u64
+values.  If start is equal to end only print the start value.
+
+Passed by reference.
+
 DMA address types dma_addr_t
 ----------------------------
 
diff --git a/include/linux/range.h b/include/linux/range.h
index 6ad0b73cb7ad..1358d4b1807a 100644
--- a/include/linux/range.h
+++ b/include/linux/range.h
@@ -31,4 +31,10 @@ int clean_sort_range(struct range *range, int az);
 
 void sort_range(struct range *range, int nr_range);
 
+#define DEFINE_RANGE(_start, _end)		\
+(struct range) {				\
+		.start = (_start),		\
+		.end = (_end),			\
+	}
+
 #endif
diff --git a/lib/test_printf.c b/lib/test_printf.c
index 5afdf5efc627..59dbe4f9a4cb 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -432,6 +432,22 @@ struct_resource(void)
 	     "%pR", &test_resource);
 }
 
+static void __init
+struct_range(void)
+{
+	struct range test_range = DEFINE_RANGE(0xc0ffee00ba5eba11,
+					       0xc0ffee00ba5eba11);
+	test("[range 0xc0ffee00ba5eba11]", "%pra", &test_range);
+
+	test_range = DEFINE_RANGE(0xc0ffee, 0xba5eba11);
+	test("[range 0x0000000000c0ffee-0x00000000ba5eba11]",
+	     "%pra", &test_range);
+
+	test_range = DEFINE_RANGE(0xba5eba11, 0xc0ffee);
+	test("[range 0x00000000ba5eba11-0x0000000000c0ffee]",
+	     "%pra", &test_range);
+}
+
 static void __init
 addr(void)
 {
@@ -807,6 +823,7 @@ test_pointer(void)
 	symbol_ptr();
 	kernel_ptr();
 	struct_resource();
+	struct_range();
 	addr();
 	escaped_str();
 	hex_string();
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 09f022ba1c05..9e76350bd77d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1039,6 +1039,20 @@ static const struct printf_spec default_dec04_spec = {
 	.flags = ZEROPAD,
 };
 
+static noinline_for_stack
+char *hex_range(char *buf, char *end, u64 start_val, u64 end_val,
+		struct printf_spec spec)
+{
+	buf = number(buf, end, start_val, spec);
+	if (start_val == end_val)
+		return buf;
+
+	if (buf < end)
+		*buf = '-';
+	++buf;
+	return number(buf, end, end_val, spec);
+}
+
 static noinline_for_stack
 char *resource_string(char *buf, char *end, struct resource *res,
 		      struct printf_spec spec, const char *fmt)
@@ -1115,11 +1129,7 @@ char *resource_string(char *buf, char *end, struct resource *res,
 		p = string_nocheck(p, pend, "size ", str_spec);
 		p = number(p, pend, resource_size(res), *specp);
 	} else {
-		p = number(p, pend, res->start, *specp);
-		if (res->start != res->end) {
-			*p++ = '-';
-			p = number(p, pend, res->end, *specp);
-		}
+		p = hex_range(p, pend, res->start, res->end, *specp);
 	}
 	if (decode) {
 		if (res->flags & IORESOURCE_MEM_64)
@@ -1140,6 +1150,31 @@ char *resource_string(char *buf, char *end, struct resource *res,
 	return string_nocheck(buf, end, sym, spec);
 }
 
+static noinline_for_stack
+char *range_string(char *buf, char *end, const struct range *range,
+		   struct printf_spec spec, const char *fmt)
+{
+	char sym[sizeof("[range 0x0123456789abcdef-0x0123456789abcdef]")];
+	char *p = sym, *pend = sym + sizeof(sym);
+
+	struct printf_spec range_spec = {
+		.field_width = 2 + 2 * sizeof(range->start), /* 0x + 2 * 8 */
+		.flags = SPECIAL | SMALL | ZEROPAD,
+		.base = 16,
+		.precision = -1,
+	};
+
+	if (check_pointer(&buf, end, range, spec))
+		return buf;
+
+	p = string_nocheck(p, pend, "[range ", default_str_spec);
+	p = hex_range(p, pend, range->start, range->end, range_spec);
+	*p++ = ']';
+	*p = '\0';
+
+	return string_nocheck(buf, end, sym, spec);
+}
+
 static noinline_for_stack
 char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
 		 const char *fmt)
@@ -2229,6 +2264,15 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
 	return widen_string(buf, buf - buf_start, end, spec);
 }
 
+static noinline_for_stack
+char *resource_or_range(const char *fmt, char *buf, char *end, void *ptr,
+			struct printf_spec spec)
+{
+	if (*fmt == 'r' && fmt[1] == 'a')
+		return range_string(buf, end, ptr, spec, fmt);
+	return resource_string(buf, end, ptr, spec, fmt);
+}
+
 int __init no_hash_pointers_enable(char *str)
 {
 	if (no_hash_pointers)
@@ -2277,6 +2321,7 @@ 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' For struct ranges, e.g., [range 0x0000000000000000 - 0x00000000000000ff]
  * - '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
@@ -2401,7 +2446,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		return symbol_string(buf, end, ptr, spec, fmt);
 	case 'R':
 	case 'r':
-		return resource_string(buf, end, ptr, spec, fmt);
+		return resource_or_range(fmt, buf, end, ptr, spec);
 	case 'h':
 		return hex_string(buf, end, ptr, spec, fmt);
 	case 'b':

-- 
2.47.0

On Fri 2024-10-25 19:46:55, 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 needs 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.
> 
> Finally introduce DEFINE_RANGE() as a parallel to DEFINE_RES_*() and use
> it in the tests.
> 
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -2229,6 +2264,15 @@ char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
>  	return widen_string(buf, buf - buf_start, end, spec);
>  }
>  
> +static noinline_for_stack
> +char *resource_or_range(const char *fmt, char *buf, char *end, void *ptr,
> +			struct printf_spec spec)
> +{
> +	if (*fmt == 'r' && fmt[1] == 'a')

This function is called only when (*fmt == 'r'). We do not need to
check it here.

Otherwise, this function should trigger an error when (*fmt != 'r').

> +		return range_string(buf, end, ptr, spec, fmt);
> +	return resource_string(buf, end, ptr, spec, fmt);
> +}
> +
>  int __init no_hash_pointers_enable(char *str)
>  {
>  	if (no_hash_pointers)
> @@ -2277,6 +2321,7 @@ 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' For struct ranges, e.g., [range 0x0000000000000000 - 0x00000000000000ff]

The range is printed without the space ' ' around the dash '-'.
I mean that this should be:

 * - 'ra' For struct ranges, e.g., [range 0x0000000000000000-0x00000000000000ff]

>   * - '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


Otherwise, the patch looks good.

I am sorry for the late reply. I had vacation... The problems are
rather cosmetic and could be fixed by a followup patch later.

Best Regards,
Petr

On Fri, Oct 25, 2024 at 07:46:55PM -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

Missing period at the end.

> A few alternatives were considered including '%par', '%r', and '%pn'.
> %pra follows that struct range is similar to struct resource (%p[rR])
> but needs 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.
> 
> Finally introduce DEFINE_RANGE() as a parallel to DEFINE_RES_*() and use
> it in the tests.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko