[PATCH v2 0/4] printf: Add struct range print specifier

[PATCH v2 0/4] printf: Add struct range print specifier

[Ira Weiny]

Support for the Compute Express Link (CXL) Dynamic Capacity Devices
(DCD) have grown a number of uses to print struct range.[1]  Support for
a printf specifier '%pra' was being worked within a large series and has
garnered a number of comments and discussion.

To better accelerate both features introduce a separate series to settle
the struct range print enhancement divorced from the CXL DCD feature.

Struct range is used to store a number range similar to struct resource.
Printing struct range becomes cumbersome having to specify 2 specifiers
and the members of the struct.  Furthermore, print output benefits from
using a standardized format.

Add to the pointer specifier support for struct range.  Share code with
struct resource for more standardization.  Add tests for struct resource
to help prevent regressions.

%pra was settled on as the most reasonable format in previous
discussions.[2]

Link: https://lore.kernel.org/all/20241007-dcd-type2-upstream-v4-2-c261ee6eeded@intel.com/ [1]
Link: https://lore.kernel.org/all/66cea3bf3332f_f937b29424@iweiny-mobl.notmuch/ [2]

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
Changes in v2:
- Andy: s/resource_and_range/resource_or_range/
- djbw/Petr: Address comments on documentation
- Link to v1: https://patch.msgid.link/20241018-cxl-pra-v1-0-7f49ba58208b@intel.com

---
Ira Weiny (4):
      test printf: Add very basic struct resource tests
      Documentation/printf: struct resource add start == end special case
      printf: Add print format (%pra) for struct range
      cxl/cdat: Use %pra for dpa range outputs

 Documentation/core-api/printk-formats.rst | 20 +++++++++-
 drivers/cxl/core/cdat.c                   |  8 ++--
 include/linux/range.h                     |  6 +++
 lib/test_printf.c                         | 61 +++++++++++++++++++++++++++++++
 lib/vsprintf.c                            | 57 ++++++++++++++++++++++++++---
 5 files changed, 141 insertions(+), 11 deletions(-)
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20240930-cxl-pra-53956ac5fc1e

Best regards,
-- 
Ira Weiny <ira.weiny@intel.com>

[PATCH v2 1/4] test printf: Add very basic struct resource tests

[Ira Weiny]

The printf tests for struct resource were stubbed out.  struct range
printing will leverage the struct resource implementation.

To prevent regression add some basic sanity tests for struct resource.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Acked-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20241007-dcd-type2-upstream-v4-1-c261ee6eeded@intel.com
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 lib/test_printf.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/lib/test_printf.c b/lib/test_printf.c
index 8448b6d02bd9..5afdf5efc627 100644
--- a/lib/test_printf.c
+++ b/lib/test_printf.c
@@ -386,6 +386,50 @@ kernel_ptr(void)
 static void __init
 struct_resource(void)
 {
+	struct resource test_resource = {
+		.start = 0xc0ffee00,
+		.end = 0xc0ffee00,
+		.flags = IORESOURCE_MEM,
+	};
+
+	test("[mem 0xc0ffee00 flags 0x200]",
+	     "%pr", &test_resource);
+
+	test_resource = (struct resource) {
+		.start = 0xc0ffee,
+		.end = 0xba5eba11,
+		.flags = IORESOURCE_MEM,
+	};
+	test("[mem 0x00c0ffee-0xba5eba11 flags 0x200]",
+	     "%pr", &test_resource);
+
+	test_resource = (struct resource) {
+		.start = 0xba5eba11,
+		.end = 0xc0ffee,
+		.flags = IORESOURCE_MEM,
+	};
+	test("[mem 0xba5eba11-0x00c0ffee flags 0x200]",
+	     "%pr", &test_resource);
+
+	test_resource = (struct resource) {
+		.start = 0xba5eba11,
+		.end = 0xba5eca11,
+		.flags = IORESOURCE_MEM,
+	};
+
+	test("[mem 0xba5eba11-0xba5eca11 flags 0x200]",
+	     "%pr", &test_resource);
+
+	test_resource = (struct resource) {
+		.start = 0xba11,
+		.end = 0xca10,
+		.flags = IORESOURCE_IO |
+			 IORESOURCE_DISABLED |
+			 IORESOURCE_UNSET,
+	};
+
+	test("[io  size 0x1000 disabled]",
+	     "%pR", &test_resource);
 }
 
 static void __init

-- 
2.47.0

[PATCH v2 2/4] Documentation/printf: struct resource add start == end special case

[Ira Weiny]

The code when printing a struct resource will check for start == end and
only print the start value.

Document this special case.

Suggested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 Documentation/core-api/printk-formats.rst | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 14e093da3ccd..552f51046cf3 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -209,12 +209,17 @@ Struct Resources
 ::
 
 	%pr	[mem 0x60000000-0x6fffffff flags 0x2200] or
+		[mem 0x60000000 flags 0x2200] or
 		[mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
+		[mem 0x0000000060000000 flags 0x2200]
 	%pR	[mem 0x60000000-0x6fffffff pref] or
+		[mem 0x60000000 pref] or
 		[mem 0x0000000060000000-0x000000006fffffff pref]
+		[mem 0x0000000060000000 pref]
 
 For printing struct resources. The ``R`` and ``r`` specifiers result in a
-printed resource with (R) or without (r) a decoded flags member.
+printed resource with (R) or without (r) a decoded flags member.  If start is
+equal to end only print the start value.
 
 Passed by reference.
 

-- 
2.47.0

[PATCH v2 3/4] printf: Add print format (%pra) for struct range

[Ira Weiny]

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

[PATCH v2 4/4] cxl/cdat: Use %pra for dpa range outputs

[Ira Weiny]

Now that there is a printf specifier for struct range use it to enhance
the debug output of CDAT data.

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
 drivers/cxl/core/cdat.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
index ef1621d40f05..438869df241a 100644
--- a/drivers/cxl/core/cdat.c
+++ b/drivers/cxl/core/cdat.c
@@ -247,8 +247,8 @@ static void update_perf_entry(struct device *dev, struct dsmas_entry *dent,
 	dpa_perf->dpa_range = dent->dpa_range;
 	dpa_perf->qos_class = dent->qos_class;
 	dev_dbg(dev,
-		"DSMAS: dpa: %#llx qos: %d read_bw: %d write_bw %d read_lat: %d write_lat: %d\n",
-		dent->dpa_range.start, dpa_perf->qos_class,
+		"DSMAS: dpa: %pra qos: %d read_bw: %d write_bw %d read_lat: %d write_lat: %d\n",
+		&dent->dpa_range, dpa_perf->qos_class,
 		dent->coord[ACCESS_COORDINATE_CPU].read_bandwidth,
 		dent->coord[ACCESS_COORDINATE_CPU].write_bandwidth,
 		dent->coord[ACCESS_COORDINATE_CPU].read_latency,
@@ -279,8 +279,8 @@ static void cxl_memdev_set_qos_class(struct cxl_dev_state *cxlds,
 			 range_contains(&pmem_range, &dent->dpa_range))
 			update_perf_entry(dev, dent, &mds->pmem_perf);
 		else
-			dev_dbg(dev, "no partition for dsmas dpa: %#llx\n",
-				dent->dpa_range.start);
+			dev_dbg(dev, "no partition for dsmas dpa: %pra\n",
+				&dent->dpa_range);
 	}
 }
 

-- 
2.47.0

Re: [PATCH v2 1/4] test printf: Add very basic struct resource tests

[Andy Shevchenko]

On Fri, Oct 25, 2024 at 07:46:53PM -0500, Ira Weiny wrote:
> The printf tests for struct resource were stubbed out.  struct range
> printing will leverage the struct resource implementation.
> 
> To prevent regression add some basic sanity tests for struct resource.

...

> +	struct resource test_resource = {
> +		.start = 0xc0ffee00,
> +		.end = 0xc0ffee00,
> +		.flags = IORESOURCE_MEM,
> +	};
> +
> +	test("[mem 0xc0ffee00 flags 0x200]",
> +	     "%pr", &test_resource);
> +
> +	test_resource = (struct resource) {
> +		.start = 0xc0ffee,
> +		.end = 0xba5eba11,
> +		.flags = IORESOURCE_MEM,
> +	};
> +	test("[mem 0x00c0ffee-0xba5eba11 flags 0x200]",
> +	     "%pr", &test_resource);
> +
> +	test_resource = (struct resource) {
> +		.start = 0xba5eba11,
> +		.end = 0xc0ffee,
> +		.flags = IORESOURCE_MEM,
> +	};
> +	test("[mem 0xba5eba11-0x00c0ffee flags 0x200]",
> +	     "%pr", &test_resource);
> +
> +	test_resource = (struct resource) {
> +		.start = 0xba5eba11,
> +		.end = 0xba5eca11,
> +		.flags = IORESOURCE_MEM,
> +	};
> +
> +	test("[mem 0xba5eba11-0xba5eca11 flags 0x200]",
> +	     "%pr", &test_resource);
> +
> +	test_resource = (struct resource) {
> +		.start = 0xba11,
> +		.end = 0xca10,
> +		.flags = IORESOURCE_IO |
> +			 IORESOURCE_DISABLED |
> +			 IORESOURCE_UNSET,
> +	};

I know that I have given my tag, but I just realized that you may use
DEFINE_RES_*() macros here.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/4] Documentation/printf: struct resource add start == end special case

[Andy Shevchenko]

On Fri, Oct 25, 2024 at 07:46:54PM -0500, Ira Weiny wrote:
> The code when printing a struct resource will check for start == end and
> only print the start value.
> 
> Document this special case.

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

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 3/4] printf: Add print format (%pra) for struct range

[Andy Shevchenko]

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

Re: [PATCH v2 1/4] test printf: Add very basic struct resource tests

[Ira Weiny]

Andy Shevchenko wrote:
> On Fri, Oct 25, 2024 at 07:46:53PM -0500, Ira Weiny wrote:
> > The printf tests for struct resource were stubbed out.  struct range
> > printing will leverage the struct resource implementation.
> > 
> > To prevent regression add some basic sanity tests for struct resource.
> 
> ...

[snip]

> > +
> > +	test("[mem 0xba5eba11-0xba5eca11 flags 0x200]",
> > +	     "%pr", &test_resource);
> > +
> > +	test_resource = (struct resource) {
> > +		.start = 0xba11,
> > +		.end = 0xca10,
> > +		.flags = IORESOURCE_IO |
> > +			 IORESOURCE_DISABLED |
> > +			 IORESOURCE_UNSET,
> > +	};
> 
> I know that I have given my tag, but I just realized that you may use
> DEFINE_RES_*() macros here.

I tried that but it does not really make things easier IMO.  So I kept it
this way.

I'd like Dave to pick up this series for 6.13.  If he can then I can use
it for the DCD work.  Otherwise DCD can go ahead of this.

Ira

Re: [PATCH v2 2/4] Documentation/printf: struct resource add start == end special case

[Jonathan Cameron]

On Fri, 25 Oct 2024 19:46:54 -0500
Ira Weiny <ira.weiny@intel.com> wrote:

> The code when printing a struct resource will check for start == end and
> only print the start value.
> 
> Document this special case.
> 
> Suggested-by: Petr Mladek <pmladek@suse.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
FWIW LGTM
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Re: [PATCH v2 0/4] printf: Add struct range print specifier

[metux]

On 26.10.24 02:46, Ira Weiny wrote:
> Support for the Compute Express Link (CXL) Dynamic Capacity Devices
> (DCD) have grown a number of uses to print struct range.[1]  Support for
> a printf specifier '%pra' was being worked within a large series and has
> garnered a number of comments and discussion.

This is just printing out hex dump of a memory range, correct ?

What I'm looking for quite some time is a sane way for dumping structs
in a human readable form (field: value pairs, using their actual types
eg. int vs string, ...).

Any idea to do that in a generic way ?
(potentially using debug info ?)


--mtx

Re: [PATCH v2 0/4] printf: Add struct range print specifier

[Ira Weiny]

metux wrote:
> On 26.10.24 02:46, Ira Weiny wrote:
> > Support for the Compute Express Link (CXL) Dynamic Capacity Devices
> > (DCD) have grown a number of uses to print struct range.[1]  Support for
> > a printf specifier '%pra' was being worked within a large series and has
> > garnered a number of comments and discussion.
> 
> This is just printing out hex dump of a memory range, correct ?

No.  This prints the struct range values not the data.

> 
> What I'm looking for quite some time is a sane way for dumping structs
> in a human readable form (field: value pairs, using their actual types
> eg. int vs string, ...).
>
> Any idea to do that in a generic way ?
> (potentially using debug info ?)
> 

For printing buffers less than 64 bytes look at:[1]

 %*ph

or bigger buffers

print_hex_dump()

Ira

[1] https://www.kernel.org/doc/html/latest/core-api/printk-formats.html

Re: [PATCH v2 2/4] Documentation/printf: struct resource add start == end special case

[Petr Mladek]

On Fri 2024-10-25 19:46:54, Ira Weiny wrote:
> The code when printing a struct resource will check for start == end and
> only print the start value.
> 
> Document this special case.
> 
> Suggested-by: Petr Mladek <pmladek@suse.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>

Looks good.

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr

Re: [PATCH v2 3/4] printf: Add print format (%pra) for struct range

[Petr Mladek]

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

Re: [PATCH v2 0/4] printf: Add struct range print specifier

[Petr Mladek]

On Wed 2024-10-30 11:51:54, metux wrote:
> On 26.10.24 02:46, Ira Weiny wrote:
> > Support for the Compute Express Link (CXL) Dynamic Capacity Devices
> > (DCD) have grown a number of uses to print struct range.[1]  Support for
> > a printf specifier '%pra' was being worked within a large series and has
> > garnered a number of comments and discussion.
> 
> This is just printing out hex dump of a memory range, correct ?
> 
> What I'm looking for quite some time is a sane way for dumping structs
> in a human readable form (field: value pairs, using their actual types
> eg. int vs string, ...).

You like to print it similar way like "gdb" or other debugging tools do.
Do I get it correctly, please?

> Any idea to do that in a generic way ?
> (potentially using debug info ?)

I am afraid that a generic solution would really need to work with
a debuginfo.

That said, there exists some generic approaches for printing various
values in the trace code, for example, see

    Documentation/trace/kprobetrace.rst
    Documentation/trace/events.rst

Best Regards,
Petr