[PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Paul Kocialkowski]

Open firmware is already using the serial-number property for passing the
device's serial number from the bootloader to the kernel. In addition, lshw
already has support for scanning this property.

The serial number is a string that somewhat represents the device's serial
number. It might come from some form of storage (e.g. an eeprom) and be
programmed at factory-time by the manufacturer or come from identification
bits available in e.g. the SoC (note that the soc_id property in the SoC bus
should hold a full account of those bits).

The serial number is taken as-is from the bootloader, so it is up to the
bootloader to define where the serial number comes from and what length it
should be. Some use cases for the serial number require it to have a maximum
length (e.g. for USB serial number) and some other cases imply more restrictions
on what the serial number should look like (e.g. in Android, the ro.serialno
property is usually a 16-bytes (plus one null byte) representation of a 64 bit
number).

Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>
---
 Documentation/devicetree/booting-without-of.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
index 7768518..95fc385 100644
--- a/Documentation/devicetree/booting-without-of.txt
+++ b/Documentation/devicetree/booting-without-of.txt
@@ -828,6 +828,10 @@ address which can extend beyond that limit.
   name may clash with standard defined ones, you prefix them with your
   vendor name and a comma.
 
+  Additional properties for the root node:
+
+    - serial-number : a string representing the device's serial number
+
   b) The /cpus node
 
   This node is the parent of all individual CPU nodes. It doesn't
-- 
1.9.1

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[PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Paul Kocialkowski]

Open firmware is already using the serial-number property for passing the
device's serial number from the bootloader to the kernel. In addition, lshw
already has support for scanning this property.

The serial number is a string that somewhat represents the device's serial
number. It might come from some form of storage (e.g. an eeprom) and be
programmed at factory-time by the manufacturer or come from identification
bits available in e.g. the SoC (note that the soc_id property in the SoC bus
should hold a full account of those bits).

The serial number is taken as-is from the bootloader, so it is up to the
bootloader to define where the serial number comes from and what length it
should be. Some use cases for the serial number require it to have a maximum
length (e.g. for USB serial number) and some other cases imply more restrictions
on what the serial number should look like (e.g. in Android, the ro.serialno
property is usually a 16-bytes (plus one null byte) representation of a 64 bit
number).

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
---
 Documentation/devicetree/booting-without-of.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
index 7768518..95fc385 100644
--- a/Documentation/devicetree/booting-without-of.txt
+++ b/Documentation/devicetree/booting-without-of.txt
@@ -828,6 +828,10 @@ address which can extend beyond that limit.
   name may clash with standard defined ones, you prefix them with your
   vendor name and a comma.
 
+  Additional properties for the root node:
+
+    - serial-number : a string representing the device's serial number
+
   b) The /cpus node
 
   This node is the parent of all individual CPU nodes. It doesn't
-- 
1.9.1

[PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Paul Kocialkowski]

This grabs the serial number shown in cpuinfo from the serial-number devicetree
property in priority. When booting with ATAGs (and without device-tree), the
provided number is still shown instead.

Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>
---
 arch/arm/include/asm/system_info.h |  1 +
 arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
index 720ea03..3860cbd40 100644
--- a/arch/arm/include/asm/system_info.h
+++ b/arch/arm/include/asm/system_info.h
@@ -17,6 +17,7 @@
 
 /* information about the system we're running on */
 extern unsigned int system_rev;
+extern const char *system_serial;
 extern unsigned int system_serial_low;
 extern unsigned int system_serial_high;
 extern unsigned int mem_fclk_21285;
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 1d60beb..b501754 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
 unsigned int system_rev;
 EXPORT_SYMBOL(system_rev);
 
+const char *system_serial;
+EXPORT_SYMBOL(system_serial);
+
 unsigned int system_serial_low;
 EXPORT_SYMBOL(system_serial_low);
 
@@ -821,8 +824,25 @@ arch_initcall(customize_machine);
 
 static int __init init_machine_late(void)
 {
+	struct device_node *root;
+	int ret;
+
 	if (machine_desc->init_late)
 		machine_desc->init_late();
+
+	root = of_find_node_by_path("/");
+	if (root) {
+		ret = of_property_read_string(root, "serial-number",
+					      &system_serial);
+		if (ret)
+			system_serial = NULL;
+	}
+
+	if (!system_serial)
+		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
+					  system_serial_high,
+					  system_serial_low);
+
 	return 0;
 }
 late_initcall(init_machine_late);
@@ -1091,8 +1111,7 @@ static int c_show(struct seq_file *m, void *v)
 
 	seq_printf(m, "Hardware\t: %s\n", machine_name);
 	seq_printf(m, "Revision\t: %04x\n", system_rev);
-	seq_printf(m, "Serial\t\t: %08x%08x\n",
-		   system_serial_high, system_serial_low);
+	seq_printf(m, "Serial\t\t: %s\n", system_serial);
 
 	return 0;
 }
-- 
1.9.1

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[PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Paul Kocialkowski]

This grabs the serial number shown in cpuinfo from the serial-number devicetree
property in priority. When booting with ATAGs (and without device-tree), the
provided number is still shown instead.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
---
 arch/arm/include/asm/system_info.h |  1 +
 arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
index 720ea03..3860cbd40 100644
--- a/arch/arm/include/asm/system_info.h
+++ b/arch/arm/include/asm/system_info.h
@@ -17,6 +17,7 @@
 
 /* information about the system we're running on */
 extern unsigned int system_rev;
+extern const char *system_serial;
 extern unsigned int system_serial_low;
 extern unsigned int system_serial_high;
 extern unsigned int mem_fclk_21285;
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 1d60beb..b501754 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
 unsigned int system_rev;
 EXPORT_SYMBOL(system_rev);
 
+const char *system_serial;
+EXPORT_SYMBOL(system_serial);
+
 unsigned int system_serial_low;
 EXPORT_SYMBOL(system_serial_low);
 
@@ -821,8 +824,25 @@ arch_initcall(customize_machine);
 
 static int __init init_machine_late(void)
 {
+	struct device_node *root;
+	int ret;
+
 	if (machine_desc->init_late)
 		machine_desc->init_late();
+
+	root = of_find_node_by_path("/");
+	if (root) {
+		ret = of_property_read_string(root, "serial-number",
+					      &system_serial);
+		if (ret)
+			system_serial = NULL;
+	}
+
+	if (!system_serial)
+		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
+					  system_serial_high,
+					  system_serial_low);
+
 	return 0;
 }
 late_initcall(init_machine_late);
@@ -1091,8 +1111,7 @@ static int c_show(struct seq_file *m, void *v)
 
 	seq_printf(m, "Hardware\t: %s\n", machine_name);
 	seq_printf(m, "Revision\t: %04x\n", system_rev);
-	seq_printf(m, "Serial\t\t: %08x%08x\n",
-		   system_serial_high, system_serial_low);
+	seq_printf(m, "Serial\t\t: %s\n", system_serial);
 
 	return 0;
 }
-- 
1.9.1

Re: [PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Rob Herring]

On Tue, Apr 28, 2015 at 2:29 AM, Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org> wrote:
> Open firmware is already using the serial-number property for passing the
> device's serial number from the bootloader to the kernel. In addition, lshw
> already has support for scanning this property.
>
> The serial number is a string that somewhat represents the device's serial
> number. It might come from some form of storage (e.g. an eeprom) and be
> programmed at factory-time by the manufacturer or come from identification
> bits available in e.g. the SoC (note that the soc_id property in the SoC bus
> should hold a full account of those bits).
>
> The serial number is taken as-is from the bootloader, so it is up to the
> bootloader to define where the serial number comes from and what length it
> should be. Some use cases for the serial number require it to have a maximum
> length (e.g. for USB serial number) and some other cases imply more restrictions
> on what the serial number should look like (e.g. in Android, the ro.serialno
> property is usually a 16-bytes (plus one null byte) representation of a 64 bit
> number).
>
> Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>

Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

What Russell was referring to for submitting is his patch tracker:

http://www.arm.linux.org.uk/developer/patches/

Rob

> ---
>  Documentation/devicetree/booting-without-of.txt | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
> index 7768518..95fc385 100644
> --- a/Documentation/devicetree/booting-without-of.txt
> +++ b/Documentation/devicetree/booting-without-of.txt
> @@ -828,6 +828,10 @@ address which can extend beyond that limit.
>    name may clash with standard defined ones, you prefix them with your
>    vendor name and a comma.
>
> +  Additional properties for the root node:
> +
> +    - serial-number : a string representing the device's serial number
> +
>    b) The /cpus node
>
>    This node is the parent of all individual CPU nodes. It doesn't
> --
> 1.9.1
>
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[PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Rob Herring]

On Tue, Apr 28, 2015 at 2:29 AM, Paul Kocialkowski <contact@paulk.fr> wrote:
> Open firmware is already using the serial-number property for passing the
> device's serial number from the bootloader to the kernel. In addition, lshw
> already has support for scanning this property.
>
> The serial number is a string that somewhat represents the device's serial
> number. It might come from some form of storage (e.g. an eeprom) and be
> programmed at factory-time by the manufacturer or come from identification
> bits available in e.g. the SoC (note that the soc_id property in the SoC bus
> should hold a full account of those bits).
>
> The serial number is taken as-is from the bootloader, so it is up to the
> bootloader to define where the serial number comes from and what length it
> should be. Some use cases for the serial number require it to have a maximum
> length (e.g. for USB serial number) and some other cases imply more restrictions
> on what the serial number should look like (e.g. in Android, the ro.serialno
> property is usually a 16-bytes (plus one null byte) representation of a 64 bit
> number).
>
> Signed-off-by: Paul Kocialkowski <contact@paulk.fr>

Acked-by: Rob Herring <robh@kernel.org>

What Russell was referring to for submitting is his patch tracker:

http://www.arm.linux.org.uk/developer/patches/

Rob

> ---
>  Documentation/devicetree/booting-without-of.txt | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
> index 7768518..95fc385 100644
> --- a/Documentation/devicetree/booting-without-of.txt
> +++ b/Documentation/devicetree/booting-without-of.txt
> @@ -828,6 +828,10 @@ address which can extend beyond that limit.
>    name may clash with standard defined ones, you prefix them with your
>    vendor name and a comma.
>
> +  Additional properties for the root node:
> +
> +    - serial-number : a string representing the device's serial number
> +
>    b) The /cpus node
>
>    This node is the parent of all individual CPU nodes. It doesn't
> --
> 1.9.1
>

Re: [PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Paul Kocialkowski]

[-- Attachment #1: Type: text/plain, Size: 2427 bytes --]

Le mercredi 06 mai 2015 à 08:26 -0500, Rob Herring a écrit :
> On Tue, Apr 28, 2015 at 2:29 AM, Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org> wrote:
> > Open firmware is already using the serial-number property for passing the
> > device's serial number from the bootloader to the kernel. In addition, lshw
> > already has support for scanning this property.
> >
> > The serial number is a string that somewhat represents the device's serial
> > number. It might come from some form of storage (e.g. an eeprom) and be
> > programmed at factory-time by the manufacturer or come from identification
> > bits available in e.g. the SoC (note that the soc_id property in the SoC bus
> > should hold a full account of those bits).
> >
> > The serial number is taken as-is from the bootloader, so it is up to the
> > bootloader to define where the serial number comes from and what length it
> > should be. Some use cases for the serial number require it to have a maximum
> > length (e.g. for USB serial number) and some other cases imply more restrictions
> > on what the serial number should look like (e.g. in Android, the ro.serialno
> > property is usually a 16-bytes (plus one null byte) representation of a 64 bit
> > number).
> >
> > Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>
> 
> Acked-by: Rob Herring <robh-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> 
> What Russell was referring to for submitting is his patch tracker:
> 
> http://www.arm.linux.org.uk/developer/patches/

Thanks for the hint, that's done now.

> > ---
> >  Documentation/devicetree/booting-without-of.txt | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
> > index 7768518..95fc385 100644
> > --- a/Documentation/devicetree/booting-without-of.txt
> > +++ b/Documentation/devicetree/booting-without-of.txt
> > @@ -828,6 +828,10 @@ address which can extend beyond that limit.
> >    name may clash with standard defined ones, you prefix them with your
> >    vendor name and a comma.
> >
> > +  Additional properties for the root node:
> > +
> > +    - serial-number : a string representing the device's serial number
> > +
> >    b) The /cpus node
> >
> >    This node is the parent of all individual CPU nodes. It doesn't
> > --
> > 1.9.1
> >


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[PATCH v4 1/2] Documentation: devicetree: root node serial-number property documentation

[Paul Kocialkowski]

Le mercredi 06 mai 2015 ? 08:26 -0500, Rob Herring a ?crit :
> On Tue, Apr 28, 2015 at 2:29 AM, Paul Kocialkowski <contact@paulk.fr> wrote:
> > Open firmware is already using the serial-number property for passing the
> > device's serial number from the bootloader to the kernel. In addition, lshw
> > already has support for scanning this property.
> >
> > The serial number is a string that somewhat represents the device's serial
> > number. It might come from some form of storage (e.g. an eeprom) and be
> > programmed at factory-time by the manufacturer or come from identification
> > bits available in e.g. the SoC (note that the soc_id property in the SoC bus
> > should hold a full account of those bits).
> >
> > The serial number is taken as-is from the bootloader, so it is up to the
> > bootloader to define where the serial number comes from and what length it
> > should be. Some use cases for the serial number require it to have a maximum
> > length (e.g. for USB serial number) and some other cases imply more restrictions
> > on what the serial number should look like (e.g. in Android, the ro.serialno
> > property is usually a 16-bytes (plus one null byte) representation of a 64 bit
> > number).
> >
> > Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
> 
> Acked-by: Rob Herring <robh@kernel.org>
> 
> What Russell was referring to for submitting is his patch tracker:
> 
> http://www.arm.linux.org.uk/developer/patches/

Thanks for the hint, that's done now.

> > ---
> >  Documentation/devicetree/booting-without-of.txt | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
> > index 7768518..95fc385 100644
> > --- a/Documentation/devicetree/booting-without-of.txt
> > +++ b/Documentation/devicetree/booting-without-of.txt
> > @@ -828,6 +828,10 @@ address which can extend beyond that limit.
> >    name may clash with standard defined ones, you prefix them with your
> >    vendor name and a comma.
> >
> > +  Additional properties for the root node:
> > +
> > +    - serial-number : a string representing the device's serial number
> > +
> >    b) The /cpus node
> >
> >    This node is the parent of all individual CPU nodes. It doesn't
> > --
> > 1.9.1
> >

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Re: [PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Grant Likely]

On Tue, 28 Apr 2015 09:29:56 +0200
, Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>
 wrote:
> This grabs the serial number shown in cpuinfo from the serial-number devicetree
> property in priority. When booting with ATAGs (and without device-tree), the
> provided number is still shown instead.
> 
> Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@public.gmane.org>

One comment below, but otherwise:

Acked-by: Grant Likely <grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

> ---
>  arch/arm/include/asm/system_info.h |  1 +
>  arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
>  2 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
> index 720ea03..3860cbd40 100644
> --- a/arch/arm/include/asm/system_info.h
> +++ b/arch/arm/include/asm/system_info.h
> @@ -17,6 +17,7 @@
>  
>  /* information about the system we're running on */
>  extern unsigned int system_rev;
> +extern const char *system_serial;
>  extern unsigned int system_serial_low;
>  extern unsigned int system_serial_high;
>  extern unsigned int mem_fclk_21285;
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 1d60beb..b501754 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
>  unsigned int system_rev;
>  EXPORT_SYMBOL(system_rev);
>  
> +const char *system_serial;
> +EXPORT_SYMBOL(system_serial);
> +

Is there any need to export this symbol? It's only used by built-in
code. Not by modules.

>  unsigned int system_serial_low;
>  EXPORT_SYMBOL(system_serial_low);
>  
> @@ -821,8 +824,25 @@ arch_initcall(customize_machine);
>  
>  static int __init init_machine_late(void)
>  {
> +	struct device_node *root;
> +	int ret;
> +
>  	if (machine_desc->init_late)
>  		machine_desc->init_late();
> +
> +	root = of_find_node_by_path("/");
> +	if (root) {
> +		ret = of_property_read_string(root, "serial-number",
> +					      &system_serial);

of_property_read_string() will not modify the argument on failure. If
system_serial is initialized to NULL, then the failure path is
unnecessary.

> +		if (ret)
> +			system_serial = NULL;
> +	}

Calls to of_find_node* functions increment the refcount for the node.
Need an of_node_put() here, or just use the of_root pointer directly. It
is safe to call of_property_read_string() with a NULL node pointer too,
it will fail gracefully.

So, the whole thing can safely boil down to:

	of_property_read_string(of_root, "serial-number", &system_serial);
	if (!system_serial)
		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
					  system_serial_high, system_serial_low);

g.

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[PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Grant Likely]

On Tue, 28 Apr 2015 09:29:56 +0200
, Paul Kocialkowski <contact@paulk.fr>
 wrote:
> This grabs the serial number shown in cpuinfo from the serial-number devicetree
> property in priority. When booting with ATAGs (and without device-tree), the
> provided number is still shown instead.
> 
> Signed-off-by: Paul Kocialkowski <contact@paulk.fr>

One comment below, but otherwise:

Acked-by: Grant Likely <grant.likely@linaro.org>

> ---
>  arch/arm/include/asm/system_info.h |  1 +
>  arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
>  2 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
> index 720ea03..3860cbd40 100644
> --- a/arch/arm/include/asm/system_info.h
> +++ b/arch/arm/include/asm/system_info.h
> @@ -17,6 +17,7 @@
>  
>  /* information about the system we're running on */
>  extern unsigned int system_rev;
> +extern const char *system_serial;
>  extern unsigned int system_serial_low;
>  extern unsigned int system_serial_high;
>  extern unsigned int mem_fclk_21285;
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 1d60beb..b501754 100644
> --- a/arch/arm/kernel/setup.c
> +++ b/arch/arm/kernel/setup.c
> @@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
>  unsigned int system_rev;
>  EXPORT_SYMBOL(system_rev);
>  
> +const char *system_serial;
> +EXPORT_SYMBOL(system_serial);
> +

Is there any need to export this symbol? It's only used by built-in
code. Not by modules.

>  unsigned int system_serial_low;
>  EXPORT_SYMBOL(system_serial_low);
>  
> @@ -821,8 +824,25 @@ arch_initcall(customize_machine);
>  
>  static int __init init_machine_late(void)
>  {
> +	struct device_node *root;
> +	int ret;
> +
>  	if (machine_desc->init_late)
>  		machine_desc->init_late();
> +
> +	root = of_find_node_by_path("/");
> +	if (root) {
> +		ret = of_property_read_string(root, "serial-number",
> +					      &system_serial);

of_property_read_string() will not modify the argument on failure. If
system_serial is initialized to NULL, then the failure path is
unnecessary.

> +		if (ret)
> +			system_serial = NULL;
> +	}

Calls to of_find_node* functions increment the refcount for the node.
Need an of_node_put() here, or just use the of_root pointer directly. It
is safe to call of_property_read_string() with a NULL node pointer too,
it will fail gracefully.

So, the whole thing can safely boil down to:

	of_property_read_string(of_root, "serial-number", &system_serial);
	if (!system_serial)
		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
					  system_serial_high, system_serial_low);

g.

Re: [PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Paul Kocialkowski]

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Le dimanche 07 juin 2015 à 18:03 +0100, Grant Likely a écrit :
> On Tue, 28 Apr 2015 09:29:56 +0200
> , Paul Kocialkowski <contact@paulk.fr>
>  wrote:
> > This grabs the serial number shown in cpuinfo from the serial-number devicetree
> > property in priority. When booting with ATAGs (and without device-tree), the
> > provided number is still shown instead.
> > 
> > Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
> 
> One comment below, but otherwise:
> 
> Acked-by: Grant Likely <grant.likely@linaro.org>

I'm afraid this was merged in Russell's tree already:
http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?h=for-next&id=3f599875e5202986b350618a617527ab441bf206

Still, it might be useful to make another patch on top with your
comments!

> > ---
> >  arch/arm/include/asm/system_info.h |  1 +
> >  arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
> >  2 files changed, 22 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
> > index 720ea03..3860cbd40 100644
> > --- a/arch/arm/include/asm/system_info.h
> > +++ b/arch/arm/include/asm/system_info.h
> > @@ -17,6 +17,7 @@
> >  
> >  /* information about the system we're running on */
> >  extern unsigned int system_rev;
> > +extern const char *system_serial;
> >  extern unsigned int system_serial_low;
> >  extern unsigned int system_serial_high;
> >  extern unsigned int mem_fclk_21285;
> > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> > index 1d60beb..b501754 100644
> > --- a/arch/arm/kernel/setup.c
> > +++ b/arch/arm/kernel/setup.c
> > @@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
> >  unsigned int system_rev;
> >  EXPORT_SYMBOL(system_rev);
> >  
> > +const char *system_serial;
> > +EXPORT_SYMBOL(system_serial);
> > +
> 
> Is there any need to export this symbol? It's only used by built-in
> code. Not by modules.

I agree, but I thought it would be consistent with the way
system_serial_high/low are exported. I'm not sure this was ever needed
either, but generally, I guess it makes sense to export parameters that
are passed to the kernel (it was through ATAGs before, now it's through
device-tree, but the logic remains the same).

> >  unsigned int system_serial_low;
> >  EXPORT_SYMBOL(system_serial_low);
> >  
> > @@ -821,8 +824,25 @@ arch_initcall(customize_machine);
> >  
> >  static int __init init_machine_late(void)
> >  {
> > +	struct device_node *root;
> > +	int ret;
> > +
> >  	if (machine_desc->init_late)
> >  		machine_desc->init_late();
> > +
> > +	root = of_find_node_by_path("/");
> > +	if (root) {
> > +		ret = of_property_read_string(root, "serial-number",
> > +					      &system_serial);
> 
> of_property_read_string() will not modify the argument on failure. If
> system_serial is initialized to NULL, then the failure path is
> unnecessary.

Makes sense.

> > +		if (ret)
> > +			system_serial = NULL;
> > +	}
> 
> Calls to of_find_node* functions increment the refcount for the node.
> Need an of_node_put() here, or just use the of_root pointer directly. It
> is safe to call of_property_read_string() with a NULL node pointer too,
> it will fail gracefully.
> 
> So, the whole thing can safely boil down to:
> 
> 	of_property_read_string(of_root, "serial-number", &system_serial);
> 	if (!system_serial)
> 		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
> 					  system_serial_high, system_serial_low);

Looks good to me, feel free to commit this change, on top of:
http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?h=for-next&id=3f599875e5202986b350618a617527ab441bf206

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[PATCH v4 2/2] arch: arm: Show the serial number from devicetree in cpuinfo

[Paul Kocialkowski]

Le dimanche 07 juin 2015 ? 18:03 +0100, Grant Likely a ?crit :
> On Tue, 28 Apr 2015 09:29:56 +0200
> , Paul Kocialkowski <contact@paulk.fr>
>  wrote:
> > This grabs the serial number shown in cpuinfo from the serial-number devicetree
> > property in priority. When booting with ATAGs (and without device-tree), the
> > provided number is still shown instead.
> > 
> > Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
> 
> One comment below, but otherwise:
> 
> Acked-by: Grant Likely <grant.likely@linaro.org>

I'm afraid this was merged in Russell's tree already:
http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?h=for-next&id=3f599875e5202986b350618a617527ab441bf206

Still, it might be useful to make another patch on top with your
comments!

> > ---
> >  arch/arm/include/asm/system_info.h |  1 +
> >  arch/arm/kernel/setup.c            | 23 +++++++++++++++++++++--
> >  2 files changed, 22 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm/include/asm/system_info.h b/arch/arm/include/asm/system_info.h
> > index 720ea03..3860cbd40 100644
> > --- a/arch/arm/include/asm/system_info.h
> > +++ b/arch/arm/include/asm/system_info.h
> > @@ -17,6 +17,7 @@
> >  
> >  /* information about the system we're running on */
> >  extern unsigned int system_rev;
> > +extern const char *system_serial;
> >  extern unsigned int system_serial_low;
> >  extern unsigned int system_serial_high;
> >  extern unsigned int mem_fclk_21285;
> > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> > index 1d60beb..b501754 100644
> > --- a/arch/arm/kernel/setup.c
> > +++ b/arch/arm/kernel/setup.c
> > @@ -93,6 +93,9 @@ unsigned int __atags_pointer __initdata;
> >  unsigned int system_rev;
> >  EXPORT_SYMBOL(system_rev);
> >  
> > +const char *system_serial;
> > +EXPORT_SYMBOL(system_serial);
> > +
> 
> Is there any need to export this symbol? It's only used by built-in
> code. Not by modules.

I agree, but I thought it would be consistent with the way
system_serial_high/low are exported. I'm not sure this was ever needed
either, but generally, I guess it makes sense to export parameters that
are passed to the kernel (it was through ATAGs before, now it's through
device-tree, but the logic remains the same).

> >  unsigned int system_serial_low;
> >  EXPORT_SYMBOL(system_serial_low);
> >  
> > @@ -821,8 +824,25 @@ arch_initcall(customize_machine);
> >  
> >  static int __init init_machine_late(void)
> >  {
> > +	struct device_node *root;
> > +	int ret;
> > +
> >  	if (machine_desc->init_late)
> >  		machine_desc->init_late();
> > +
> > +	root = of_find_node_by_path("/");
> > +	if (root) {
> > +		ret = of_property_read_string(root, "serial-number",
> > +					      &system_serial);
> 
> of_property_read_string() will not modify the argument on failure. If
> system_serial is initialized to NULL, then the failure path is
> unnecessary.

Makes sense.

> > +		if (ret)
> > +			system_serial = NULL;
> > +	}
> 
> Calls to of_find_node* functions increment the refcount for the node.
> Need an of_node_put() here, or just use the of_root pointer directly. It
> is safe to call of_property_read_string() with a NULL node pointer too,
> it will fail gracefully.
> 
> So, the whole thing can safely boil down to:
> 
> 	of_property_read_string(of_root, "serial-number", &system_serial);
> 	if (!system_serial)
> 		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
> 					  system_serial_high, system_serial_low);

Looks good to me, feel free to commit this change, on top of:
http://ftp.arm.linux.org.uk/cgit/linux-arm.git/commit/?h=for-next&id=3f599875e5202986b350618a617527ab441bf206
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