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

[Russell King - ARM Linux]

On Sat, Mar 28, 2015 at 06:39:31PM +0100, Paul Kocialkowski 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 at paulk.fr>
> ---
>  arch/arm/include/asm/system_info.h |  1 +
>  arch/arm/kernel/atags_parse.c      |  3 +++
>  arch/arm/kernel/devtree.c          | 15 ++++++++++-----
>  arch/arm/kernel/setup.c            | 11 +++++++++--
>  4 files changed, 23 insertions(+), 7 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/atags_parse.c b/arch/arm/kernel/atags_parse.c
> index 68c6ae0..8384818 100644
> --- a/arch/arm/kernel/atags_parse.c
> +++ b/arch/arm/kernel/atags_parse.c
> @@ -231,6 +231,9 @@ setup_machine_tags(phys_addr_t __atags_pointer, unsigned int machine_nr)
>  		parse_tags(tags);
>  	}
>  
> +	/* Serial number is stored in system_serial_low/high */
> +	system_serial = NULL;
> +
>  	/* parse_early_param needs a boot_command_line */
>  	strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);
>  
> diff --git a/arch/arm/kernel/devtree.c b/arch/arm/kernel/devtree.c
> index 11c54de..a82a04d 100644
> --- a/arch/arm/kernel/devtree.c
> +++ b/arch/arm/kernel/devtree.c
> @@ -26,6 +26,7 @@
>  #include <asm/smp_plat.h>
>  #include <asm/mach/arch.h>
>  #include <asm/mach-types.h>
> +#include <asm/system_info.h>
>  
>  
>  #ifdef CONFIG_SMP
> @@ -204,6 +205,9 @@ static const void * __init arch_get_next_mach(const char *const **match)
>  const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
>  {
>  	const struct machine_desc *mdesc, *mdesc_best = NULL;
> +	const char *prop;
> +	int size;
> +	unsigned long dt_root;
>  
>  #ifdef CONFIG_ARCH_MULTIPLATFORM
>  	DT_MACHINE_START(GENERIC_DT, "Generic DT based system")
> @@ -215,17 +219,14 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
>  	if (!dt_phys || !early_init_dt_verify(phys_to_virt(dt_phys)))
>  		return NULL;
>  
> +	dt_root = of_get_flat_dt_root();
> +
>  	mdesc = of_flat_dt_match_machine(mdesc_best, arch_get_next_mach);
>  
>  	if (!mdesc) {
> -		const char *prop;
> -		int size;
> -		unsigned long dt_root;
> -
>  		early_print("\nError: unrecognized/unsupported "
>  			    "device tree compatible list:\n[ ");
>  
> -		dt_root = of_get_flat_dt_root();
>  		prop = of_get_flat_dt_prop(dt_root, "compatible", &size);
>  		while (size > 0) {
>  			early_print("'%s' ", prop);
> @@ -243,6 +244,10 @@ const struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
>  
>  	early_init_dt_scan_nodes();
>  
> +	/* Scan for serial number */
> +	prop = of_get_flat_dt_prop(dt_root, "serial-number", &size);
> +	system_serial = prop;
> +
>  	/* Change machine number to match the mdesc we're using */
>  	__machine_arch_type = mdesc->nr;
>  
> diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
> index 1d60beb..69fa7ef 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);
>  
> @@ -1091,8 +1094,12 @@ 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);
> +
> +	if (system_serial)
> +		seq_printf(m, "Serial\t\t: %s\n", system_serial);
> +	else
> +		seq_printf(m, "Serial\t\t: %08x%08x\n",
> +			   system_serial_high, system_serial_low);

How about this becomes just:

	seq_printf(m, "Serial\t\t: %s\n", system_serial);

And we arrange for system_serial to always be initialised later on
during boot if it's not already set from the system_serial_high and
system_serial_low variables?  Eg, adding in init_machine_late():

	if (!system_serial)
		system_serial = kasprintf(GFP_KERNEL, "%08x%08x",
					  system_serial_high,
					  system_serial_low);

and is there a reason we can't look for the serial number in DT at
this point as well - is there a reason we might need the stringified
serial number early?

-- 
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