DT printf format specifiers

Several places in DT code open code the equivalent of kbasename. Replace them.

The behavior for root nodes in node_name_cmp will be slightly different. Instead of comparing "/", "" will be compared. The comparison will be the same.

Signed-off-by Rob Herring <[email protected]>

---
 drivers/of/base.c     | 5 +----
 drivers/of/platform.c | 2 +-
 drivers/of/resolver.c | 4 ++--
 3 files changed, 4 insertions(+), 7 deletions(-)

drivers/of/base.c +1 -4

index 28d5f53bc631..054159ccd5f8 100644
@@ -773,10 +773,7 @@ static struct device_node *__of_find_node_by_path(struct device_node *parent,
                return NULL;
 
        __for_each_child_of_node(parent, child) {
-               const char *name = strrchr(child->full_name, '/');
-               if (WARN(!name, "malformed device_node %s\n", child->full_name))
-                       continue;
-               name++;
+               const char *name = kbasename(child->full_name);
                if (strncmp(path, name, len) == 0 && (strlen(name) == len))
                        return child;
        }

drivers/of/platform.c +1 -1

index 71fecc2debfc..8f73413fa243 100644
@@ -99,7 +99,7 @@ static void of_device_make_bus_id(struct device *dev)
 
                /* format arguments only used if dev_name() resolves to NULL */
                dev_set_name(dev, dev_name(dev) ? "%s:%s" : "%s",
-                            strrchr(node->full_name, '/') + 1, dev_name(dev));
+                            kbasename(node->full_name), dev_name(dev));
                node = node->parent;
        }
 }

drivers/of/resolver.c +2 -3

index 771f4844c781..63626d7d9adb 100644
@@ -165,8 +165,8 @@ static int update_usages_of_a_phandle_reference(struct device_node *overlay,
 static int node_name_cmp(const struct device_node *dn1,
                const struct device_node *dn2)
 {
-       const char *n1 = strrchr(dn1->full_name, '/') ? : "/";
-       const char *n2 = strrchr(dn2->full_name, '/') ? : "/";
+       const char *n1 = kbasename(dn1->full_name);
+       const char *n2 = kbasename(dn2->full_name);
 
        return of_node_cmp(n1, n2);
 }
--

2.11.0

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. Preparing for the eventual delayed allocation introduce a custom printk format specifier that is both more compact and more pleasant to the eye.

For instance typical use is:

	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:

	pr_info("Frobbing node %pOF\n", node);

More fine-grained control of formatting includes printing the name, flag, path-spec name, reference count and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check.

lib/vsprintf.c +0 -0

[]

lib/vsprintf.c +0 -0

@@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
 	return format_flags(buf, end, flags, names);
 }

lib/vsprintf.c +21 -0

+static noinline_for_stack
+char *device_node_string(char *buf, char *end, struct device_node *dn,
+			 struct printf_spec spec, const char *fmt)
+{
+	char tbuf[sizeof("xxxxxxxxxx") + 1];
+	const char *fmtp, *p;
+	int ret;
+	char *buf_start = buf;
+	struct property *prop;
+	bool has_mult, pass;
+	const struct printf_spec num_spec = {
+		.flags = SMALL,
+		.field_width = -1,
+		.precision = -1,
+		.base = 10,
+	};
+
+	struct printf_spec str_spec = spec;
+	str_spec.field_width = -1;
+
+	if (!IS_ENABLED(CONFIG_OF))

lib/vsprintf.c +24 -0

+		if (pass && (*fmtp != 'f')) {
+			if (buf < end)
+				*buf = '|';
+			buf++;
+		}
+
+		switch (*fmtp) {
+		case 'f':	/* full_name */
+			if (pass) {
+				if (buf < end)
+					*buf = ':';
+				buf++;
+			}
+			buf = device_node_gen_full_name(dn, buf, end);
+			break;
+		case 'n':	/* name */
+			buf = string(buf, end, dn->name, str_spec);
+			break;
+		case 'p':	/* phandle */
+			buf = number(buf, end, (unsigned int)dn->phandle, num_spec);
+			break;
+		case 'P':	/* path-spec */
+			buf = string(buf, end, kbasename(of_node_full_name(dn)), str_spec);
+			break;

Quoted 1 line · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

I think the commit subject is wrong.
It adds an "of" specific bit to vsprintf.c. The subject should be
'vsprintf: Add %p extension "%pO" for device tree'

Quoted 8 lines

90% of the usage of device node's full_name is printing it out in a kernel message. Preparing for the eventual delayed allocation introduce a custom printk format specifier that is both more compact and more pleasant to the eye.

For instance typical use is:

      pr_info("Frobbing node %s\n", node->full_name);

Quoted 2 lines

Which can be written now as:

      pr_info("Frobbing node %pOF\n", node);

Somehow I think this example is poor as node->full_name is a pretty obvious to read use. %pOF requires you to look up or know what the output is going to be.

Quoted 9 lines

More fine-grained control of formatting includes printing the name, flag, path-spec name, reference count and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check.

Some comments about the code.

Quoted 6 lines

lib/vsprintf.c +0 -0

[]

lib/vsprintf.c +0 -0

@@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
      return format_flags(buf, end, flags, names);
 }
 

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1482

Quoted 9 lines

lib/vsprintf.c +9 -0

+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+     int len, ret;
+
+     if (!np || !np->parent)
+             return buf;
+
+     buf = device_node_gen_full_name(np->parent, buf, end);

This is recursive. How many levels of parents could there be? Perhaps there should be a recursion limit.

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1488

Quoted 7 lines

lib/vsprintf.c +6 -0

+
+     if (buf < end)
+             len = end - buf;
+     else
+             len = 0;
+     ret = snprintf(buf, len, "/%s", kbasename(np->full_name));

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1494

Quoted 6 lines

lib/vsprintf.c +6 -0

+     if (ret <= 0)
+             return buf;
+     else if (len == 0 || ret < len)
+             return buf + ret;
+     return buf + len;
+}

Does this work with %p<len>OF for a right justified or padded length string? Perhaps widen_string should be added.

Quoted 21 lines

lib/vsprintf.c +21 -0

+static noinline_for_stack
+char *device_node_string(char *buf, char *end, struct device_node *dn,
+                      struct printf_spec spec, const char *fmt)
+{
+     char tbuf[sizeof("xxxxxxxxxx") + 1];
+     const char *fmtp, *p;
+     int ret;
+     char *buf_start = buf;
+     struct property *prop;
+     bool has_mult, pass;
+     const struct printf_spec num_spec = {
+             .flags = SMALL,
+             .field_width = -1,
+             .precision = -1,
+             .base = 10,
+     };
+
+     struct printf_spec str_spec = spec;
+     str_spec.field_width = -1;
+
+     if (!IS_ENABLED(CONFIG_OF))

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1526

Quoted 10 lines

lib/vsprintf.c +10 -0

+             return string(buf, end, "(!OF)", spec);
+
+     if ((unsigned long)dn < PAGE_SIZE)
+             return string(buf, end, "(null)", spec);
+
+     /* simple case without anything any more format specifiers */
+     if (fmt[1] == '\0' || strcspn(fmt + 1,"fnpPFcCr") > 0)
+             fmt = "Ff";
+
+     for (fmtp = fmt + 1, pass = false; strspn(fmtp,"fnpPFcCr"); fmtp++, pass = true) {

why not

        while (isalpha(*++fmt))

like ip6 or isalnum like FORMAT_TYPE_PTR uses?

Quoted 25 lines

lib/vsprintf.c +24 -0

+             if (pass && (*fmtp != 'f')) {
+                     if (buf < end)
+                             *buf = '|';
+                     buf++;
+             }
+
+             switch (*fmtp) {
+             case 'f':       /* full_name */
+                     if (pass) {
+                             if (buf < end)
+                                     *buf = ':';
+                             buf++;
+                     }
+                     buf = device_node_gen_full_name(dn, buf, end);
+                     break;
+             case 'n':       /* name */
+                     buf = string(buf, end, dn->name, str_spec);
+                     break;
+             case 'p':       /* phandle */
+                     buf = number(buf, end, (unsigned int)dn->phandle, num_spec);
+                     break;
+             case 'P':       /* path-spec */
+                     buf = string(buf, end, kbasename(of_node_full_name(dn)), str_spec);
+                     break;

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1560

Quoted 10 lines

lib/vsprintf.c +10 -0

+             case 'F':       /* flags */
+                     snprintf(tbuf, sizeof(tbuf), "%c%c%c%c",
+                             of_node_check_flag(dn, OF_DYNAMIC) ?
+                                     'D' : '-',
+                             of_node_check_flag(dn, OF_DETACHED) ?
+                                     'd' : '-',
+                             of_node_check_flag(dn, OF_POPULATED) ?
+                                     'P' : '-',
+                             of_node_check_flag(dn,
+                                     OF_POPULATED_BUS) ?  'B' : '-');

I'd try to avoid all uses of snprintf as it's effectively another fairly
large stack frame.

It's probably better to avoid more recursion stack depth use and just use *buf++ as appropriate.

Quoted 7 lines · Joe Perches

Quoted 1 line · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

I think the commit subject is wrong.
It adds an "of" specific bit to vsprintf.c. The subject should be
'vsprintf: Add %p extension "%pO" for device tree'

Okay, but it was good enough for the 2-3 versions Pantelis did before...

Quoted 2 lines

Quoted 2 lines

90% of the usage of device node's full_name is printing it out in a kernel message. Preparing for the eventual delayed allocation

Quoted 6 lines

Quoted 6 lines

introduce a custom printk format specifier that is both more compact and more pleasant to the eye.

For instance typical use is:

      pr_info("Frobbing node %s\n", node->full_name);

Quoted 6 lines

Quoted 2 lines

Which can be written now as:

      pr_info("Frobbing node %pOF\n", node);

Somehow I think this example is poor as node->full_name is a pretty obvious to read use. %pOF requires you to look up or know what the output is going to be.

So %pOFfullname? We've beat this one to death IMO.

Quoted 17 lines

Quoted 8 lines

More fine-grained control of formatting includes printing the name, flag, path-spec name, reference count and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check.

Some comments about the code.

Quoted 6 lines

lib/vsprintf.c +0 -0

[]

lib/vsprintf.c +0 -0

@@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
      return format_flags(buf, end, flags, names);
 }
 

Quoted 12 lines

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1482

Quoted 9 lines

lib/vsprintf.c +9 -0

+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+     int len, ret;
+
+     if (!np || !np->parent)
+             return buf;
+
+     buf = device_node_gen_full_name(np->parent, buf, end);

This is recursive. How many levels of parents could there be? Perhaps there should be a recursion limit.

2-6 I'd say is typical. The FDT unflattening code limits things to 64 (which is probably way more than needed).

I could re-write it to be non-recursive, but then I'll just have the max sized array of pointers on the stack.

Quoted 11 lines

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1560

Quoted 10 lines

lib/vsprintf.c +10 -0

+             case 'F':       /* flags */
+                     snprintf(tbuf, sizeof(tbuf), "%c%c%c%c",
+                             of_node_check_flag(dn, OF_DYNAMIC) ?
+                                     'D' : '-',
+                             of_node_check_flag(dn, OF_DETACHED) ?
+                                     'd' : '-',
+                             of_node_check_flag(dn, OF_POPULATED) ?
+                                     'P' : '-',
+                             of_node_check_flag(dn,
+                                     OF_POPULATED_BUS) ?  'B' : '-');

Quoted 2 lines

I'd try to avoid all uses of snprintf as it's effectively another fairly large stack frame.

Okay.

Quoted 2 lines

It's probably better to avoid more recursion stack depth use and just use *buf++ as appropriate.

You can't use *buf++ as this code must work and increment buf even when buf is NULL.

Quoted 1 line · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

I think the commit subject is wrong.
It adds an "of" specific bit to vsprintf.c. The subject should be
'vsprintf:  Add %p extension "%pO" for device tree'

Quoted 10 lines

90% of the usage of device node's full_name is printing it out in a kernel message. Preparing for the eventual delayed allocation introduce a custom printk format specifier that is both more compact and more pleasant to the eye.

For instance typical use is:

	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:

	pr_info("Frobbing node %pOF\n", node);

Somehow I think this example is poor as node->full_name is a pretty obvious to read use. %pOF requires you to look up or know what the output is going to be.

Quoted 8 lines

More fine-grained control of formatting includes printing the name, flag, path-spec name, reference count and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check.

Some comments about the code.

Quoted 6 lines

lib/vsprintf.c +0 -0

[]

lib/vsprintf.c +0 -0

@@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
 	return format_flags(buf, end, flags, names);
 }
 

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1482

Quoted 9 lines

lib/vsprintf.c +9 -0

+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+	int len, ret;
+
+	if (!np || !np->parent)
+		return buf;
+
+	buf = device_node_gen_full_name(np->parent, buf, end);

This is recursive. How many levels of parents could there be? Perhaps there should be a recursion limit.

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1526

Quoted 5 lines

lib/vsprintf.c +5 -0

+	/* simple case without anything any more format specifiers */
+	if (fmt[1] == '\0' || strcspn(fmt + 1,"fnpPFcCr") > 0)
+		fmt = "Ff";
+
+	for (fmtp = fmt + 1, pass = false; strspn(fmtp,"fnpPFcCr"); fmtp++, pass = true) {

why not

	while (isalpha(*++fmt))

like ip6 or isalnum like FORMAT_TYPE_PTR uses?

Quoted 2 lines · Joe Perches

Quoted 1 line · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

Quoted 6 lines

Quoted 6 lines

lib/vsprintf.c +0 -0

[]

lib/vsprintf.c +0 -0

@@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
 	return format_flags(buf, end, flags, names);
 }
 

Quoted 12 lines

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1482

Quoted 9 lines

lib/vsprintf.c +9 -0

+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+	int len, ret;
+
+	if (!np || !np->parent)
+		return buf;
+
+	buf = device_node_gen_full_name(np->parent, buf, end);

This is recursive. How many levels of parents could there be? Perhaps there should be a recursion limit.

Okay, unlike unflattening code, we can easily calculate the depth and then allocate an array on the stack. So this is what I've ended up with:

static int device_node_calc_depth(const struct device_node *np)

{
	int d;

	for (d = 0; np; d++)
		np = np->parent;

	return d;
}

static noinline_for_stack
char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)

{
	int i;
	int depth = device_node_calc_depth(np);
	const struct device_node *nodes[depth];
	const struct printf_spec strspec = {
		.field_width = -1,
		.precision = -1,
	};

	if (!depth)
		return buf;
	/* special case for root node */
	if (depth == 1)
		return string(buf, end, "/", strspec);

	depth--;
	for (i = depth - 1; i >= 0; i--) {
		nodes[i] = np;

		np = np->parent;
	}
	for (i = 0; i < depth; i++) {
		buf = string(buf, end, "/", strspec);
		buf = string(buf, end, kbasename(nodes[i]->full_name), strspec);
	}
	return buf;
}

From: Pantelis Antoniou <[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. However, storing the full path for every node is wasteful and redundant. With a custom format specifier, we can generate the full path at run-time and eventually remove the full path from every node.

For instance typical use is:

	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:

	pr_info("Frobbing node %pOF\n", node);

More fine-grained control of formatting includes printing the name, flags, path-spec name and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check. The unittest code was written by Grant Likely.

Signed-off-by Pantelis Antoniou <[email protected]>

Signed-off-by Rob Herring <[email protected]>

---
I missed some comments and changes Grant had done and incorporated them.

v2:
- Change subject
- Rewrite device_node_gen_full_name() to avoid recursion.
- Avoid using sprintf.
- Add unittests Grant L. wrote.
- Drop ref count printing (from discussion 2 years ago).
- Remove fmtp local var.

 Documentation/printk-formats.txt             |  30 ++++++
 drivers/of/unittest-data/tests-platform.dtsi |   4 +-
 drivers/of/unittest.c                        |  58 +++++++++++
 lib/vsprintf.c                               | 140 +++++++++++++++++++++++++++
 scripts/checkpatch.pl                        |   2 +-
 5 files changed, 232 insertions(+), 2 deletions(-)

Documentation/printk-formats.txt +30 -0

index 5962949944fd..c7af38188f12 100644
@@ -275,6 +275,36 @@ struct va_format:
 
 	Passed by reference.
 
+Device tree nodes:
+
+	%pOn[fnpPcCF]
+
+	For printing device tree nodes. The optional arguments are:
+	    f device node full_name
+	    n device node name
+	    p device node phandle
+	    P device node path spec (name + @unit)
+	    F device node flags
+	    c major compatible string
+	    C full compatible string
+	Without any arguments prints full_name (same as %pOFf)
+	The separator when using multiple arguments is ':'
+
+	Examples:
+
+	%pOn	/foo/bar@0			- Node full name
+	%pOnf	/foo/bar@0			- Same as above
+	%pOnfp	/foo/bar@0:10			- Node full name + phandle
+	%pOnfcF	/foo/bar@0:foo,device:--P-	- Node full name +
+	                                          major compatible string +
+						  node flags
+							D - dynamic
+							d - detached
+							P - Populated
+							B - Populated bus
+
+	Passed by reference.
+
 struct clk:
 
 	%pC	pll1

Quoted 11 lines · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. However, storing the full path for every node is wasteful and redundant. With a custom format specifier, we can generate the full path at run-time and eventually remove the full path from every node.

For instance typical use is:

      pr_info("Frobbing node %s\n", node->full_name);

Quoted 2 lines

Which can be written now as:

      pr_info("Frobbing node %pOF\n", node);

isn't OF for flags -- and Of for full name?
Typo or a change in the last 2 years?

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. However, storing the full path for every node is wasteful and redundant. With a custom format specifier, we can generate the full path at run-time and eventually remove the full path from every node.

For instance typical use is:

	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:

	pr_info("Frobbing node %pOF\n", node);

lib/vsprintf.c +28 -0

@@ -1470,6 +1471,131 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
 	return format_flags(buf, end, flags, names);
 }
 
+static int device_node_calc_depth(const struct device_node *np)
+{
+	int d;
+
+	for (d = 0; np; d++)
+		np = np->parent;
+
+	return d;
+}
+
+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+	int i;
+	int depth = device_node_calc_depth(np);
+	static const struct printf_spec strspec = {
+		.field_width = -1,
+		.precision = -1,
+	};
+	const struct device_node *nodes[depth];
+
+	if (!depth)
+		returnuf;
+	/* special case for root node */
+	if (depth == 1)
+		return string(buf, end, "/", strspec);
+
+	depth--;

Quoted 11 lines · Rob Herring

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. However, storing the full path for every node is wasteful and redundant. With a custom format specifier, we can generate the full path at run-time and eventually remove the full path from every node.

For instance typical use is:

      pr_info("Frobbing node %s\n", node->full_name);

Quoted 2 lines

Which can be written now as:

      pr_info("Frobbing node %pOF\n", node);

I still think this should use another identifier like %pO for object then another letter for type of object maybe N for node.

And F is flags, f is name

lib/vsprintf.c

Quoted 1 line

lib/vsprintf.c +0 -0

[]

Quoted 32 lines

lib/vsprintf.c +28 -0

@@ -1470,6 +1471,131 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
      return format_flags(buf, end, flags, names);
 }
 
+static int device_node_calc_depth(const struct device_node *np)
+{
+     int d;
+
+     for (d = 0; np; d++)
+             np = np->parent;
+
+     return d;
+}
+
+static noinline_for_stack
+char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
+{
+     int i;
+     int depth = device_node_calc_depth(np);
+     static const struct printf_spec strspec = {
+             .field_width = -1,
+             .precision = -1,
+     };
+     const struct device_node *nodes[depth];
+
+     if (!depth)
+             returnuf;
+     /* special case for root node */
+     if (depth == 1)
+             return string(buf, end, "/", strspec);
+
+     depth--;

lib/vsprintf.c char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt) · line 1511

Quoted 10 lines

lib/vsprintf.c +10 -0

+     for (i = depth - 1; i >= 0; i--) {
+             nodes[i] = np;
+             np = np->parent;
+     }
+     for (i = 0; i < depth; i++) {
+             buf = string(buf, end, "/", strspec);
+             buf = string(buf, end, kbasename(nodes[i]->full_name), strspec);
+     }
+     return buf;
+}

I think there should be another function to get a particular struct device_node * at a particular depth to avoid all the pointers on stack.

Basically, adapt the for (i = depth - 1 loop to a function that returns nodes[i]

From: Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

90% of the usage of device node's full_name is printing it out in a kernel message. However, storing the full path for every node is wasteful and redundant. With a custom format specifier, we can generate the full path at run-time and eventually remove the full path from every node.

For instance typical use is:

	pr_info("Frobbing node %s\n", node->full_name);

Which can be written now as:

	pr_info("Frobbing node %pOF\n", node);

'%pO' is the base specifier to represent kobjects with '%pOF' representing struct device_node. Currently, struct device_node is the only supported type of kobject.

More fine-grained control of formatting includes printing the name, flags, path-spec name and others, explained in the documentation entry.

Originally written by Pantelis, but pretty much rewrote the core function using existing string/number functions. The 2 passes were unnecessary and have been removed. Also, updated the checkpatch.pl check. The unittest code was written by Grant Likely.

Signed-off-by Pantelis Antoniou <pantelis.antoniou-OWPKS81ov/FWk0Htik3J/[email protected]>

Signed-off-by Rob Herring <[email protected]>

---
v3:
- Fix missing documentation updates using '%pOF' as the device_node specifier.
- Update the commit msg and documentation to clearly define '%pO' is the base specifier for kobjects.
- Rework device_node_gen_full_name() to avoid creating an array of node pointers on the stack.

Now that we have a custom printf format specifier, convert users of full_name to use %pOF instead. This is preparation to remove storing of the full path string for each node.