[PATCH v2 02/25] printk: Add print format (%par) for struct range

[Ira Weiny <ira.weiny@intel.com>]

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 '%pn' for 'print raNge' but
%par follows that struct range is most often used to store a range of
physical addresses.  So use '%par' for 'print address range'.

To: Petr Mladek <pmladek@suse.com> (maintainer:VSPRINTF)
To: Steven Rostedt <rostedt@goodmis.org> (maintainer:VSPRINTF)
To: Jonathan Corbet <corbet@lwn.net> (maintainer:DOCUMENTATION)
Cc: linux-doc@vger.kernel.org (open list:DOCUMENTATION)
Cc: linux-kernel@vger.kernel.org (open list)
Link: https://lore.kernel.org/all/663922b475e50_d54d72945b@dwillia2-xfh.jf.intel.com.notmuch/ [1]
Suggested-by: "Dan Williams" <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 Documentation/core-api/printk-formats.rst | 14 ++++++++++++
 lib/vsprintf.c                            | 37 +++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 4451ef501936..a02ef899b2a6 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -231,6 +231,20 @@ width of the CPU data path.
 
 Passed by reference.
 
+Struct Range
+------------
+
+::
+
+	%par	[range 0x60000000-0x6fffffff] or
+		[range 0x0000000060000000-0x000000006fffffff]
+
+For printing struct range.  A variation of printing a physical address is to
+print the value of struct range which are often used to hold a physical address
+range.
+
+Passed by reference.
+
 DMA address types dma_addr_t
 ----------------------------
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 2d71b1115916..c132178fac07 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1140,6 +1140,39 @@ 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)
+{
+#define RANGE_PRINTK_SIZE		16
+#define RANGE_DECODED_BUF_SIZE		((2 * sizeof(struct range)) + 4)
+#define RANGE_PRINT_BUF_SIZE		sizeof("[range - ]")
+	char sym[RANGE_DECODED_BUF_SIZE + RANGE_PRINT_BUF_SIZE];
+	char *p = sym, *pend = sym + sizeof(sym);
+
+	static const struct printf_spec str_spec = {
+		.field_width = -1,
+		.precision = 10,
+		.flags = LEFT,
+	};
+	static const struct printf_spec range_spec = {
+		.base = 16,
+		.field_width = RANGE_PRINTK_SIZE,
+		.precision = -1,
+		.flags = SPECIAL | SMALL | ZEROPAD,
+	};
+
+	*p++ = '[';
+	p = string_nocheck(p, pend, "range ", str_spec);
+	p = number(p, pend, range->start, range_spec);
+	*p++ = '-';
+	p = number(p, pend, 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)
@@ -1802,6 +1835,8 @@ char *address_val(char *buf, char *end, const void *addr,
 		return buf;
 
 	switch (fmt[1]) {
+	case 'r':
+		return range_string(buf, end, addr, spec, fmt);
 	case 'd':
 		num = *(const dma_addr_t *)addr;
 		size = sizeof(dma_addr_t);
@@ -2364,6 +2399,8 @@ char *rust_fmt_argument(char *buf, char *end, void *ptr);
  *            to use print_hex_dump() for the larger input.
  * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
  *           (default assumed to be phys_addr_t, passed by reference)
+ * - 'ar' For decoded struct ranges (a variation of physical address which are
+ *        most often stored in struct ranges.
  * - 'd[234]' For a dentry name (optionally 2-4 last components)
  * - 'D[234]' Same as 'd' but for a struct file
  * - 'g' For block_device name (gendisk + partition number)

-- 
2.45.2