Re: [PATCH 4/7] fdt.c: Add non-boottime device tree functions

[Grant Likely <grant.likely@secretlab.ca>]

On Thu, Nov 18, 2010 at 03:54:59PM -0800, Stephen Neuendorffer wrote:
> In preparation for providing run-time handling of device trees, factor
> out some of the basic functions so that they take an arbitrary blob,
> rather than relying on the single boot-time tree.
> 
> Signed-off-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>

Thanks.  Merged, but one comment below.  Please fix with a followup patch.

g.

> 
> --
> 
> V2: functions have of_fdt_* names
>     removed find_flat_dt_string
>     blob argument is first
> ---
>  drivers/of/fdt.c       |  133 ++++++++++++++++++++++++++++-------------------
>  include/linux/of_fdt.h |   11 ++++
>  2 files changed, 90 insertions(+), 54 deletions(-)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 4d71b29..190e26c 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -22,6 +22,82 @@
>  
>  #include <asm/page.h>
>  
> +char *of_fdt_get_string(struct boot_param_header *blob, u32 offset)
> +{
> +	return ((char *)blob) +
> +		be32_to_cpu(blob->off_dt_strings) + offset;
> +}
> +
> +/**
> + * of_fdt_get_property - Given a node in the given flat blob, return
> + * the property ptr
> + */
> +void *of_fdt_get_property(struct boot_param_header *blob,
> +		       unsigned long node, const char *name,
> +		       unsigned long *size)
> +{
> +	unsigned long p = node;
> +
> +	do {
> +		u32 tag = be32_to_cpup((__be32 *)p);
> +		u32 sz, noff;
> +		const char *nstr;
> +
> +		p += 4;
> +		if (tag == OF_DT_NOP)
> +			continue;
> +		if (tag != OF_DT_PROP)
> +			return NULL;
> +
> +		sz = be32_to_cpup((__be32 *)p);
> +		noff = be32_to_cpup((__be32 *)(p + 4));
> +		p += 8;
> +		if (be32_to_cpu(blob->version) < 0x10)
> +			p = ALIGN(p, sz >= 8 ? 8 : 4);
> +
> +		nstr = of_fdt_get_string(blob, noff);
> +		if (nstr == NULL) {
> +			pr_warning("Can't find property index name !\n");
> +			return NULL;
> +		}
> +		if (strcmp(name, nstr) == 0) {
> +			if (size)
> +				*size = sz;
> +			return (void *)p;
> +		}
> +		p += sz;
> +		p = ALIGN(p, 4);
> +	} while (1);
> +}
> +
> +/**
> + * of_fdt_is_compatible - Return true if given node from the given blob has
> + * compat in its compatible list
> + * @blob: A device tree blob
> + * @node: node to test
> + * @compat: compatible string to compare with compatible list.
> + */
> +int of_fdt_is_compatible(struct boot_param_header *blob,
> +		      unsigned long node, const char *compat)
> +{
> +	const char *cp;
> +	unsigned long cplen, l;
> +
> +	cp = of_fdt_get_property(blob, node, "compatible", &cplen);
> +	if (cp == NULL)
> +		return 0;
> +	while (cplen > 0) {
> +		if (of_compat_cmp(cp, compat, strlen(compat)) == 0)
> +			return 1;

Need to verify that strlen(cp) + 1 is not larger than cplen.
Otherwise cplen could wrap around and the loop won't terminate because
cplen is an unsigned long.

> +		l = strlen(cp) + 1;
> +		cp += l;
> +		cplen -= l;
> +	}
> +
> +	return 0;
> +}
> +
> +/* Everything below here references initial_boot_params directly. */
>  int __initdata dt_root_addr_cells;
>  int __initdata dt_root_size_cells;
>  
> @@ -29,12 +105,6 @@ struct boot_param_header *initial_boot_params;
>  
>  #ifdef CONFIG_EARLY_FLATTREE
>  
> -char *find_flat_dt_string(u32 offset)
> -{
> -	return ((char *)initial_boot_params) +
> -		be32_to_cpu(initial_boot_params->off_dt_strings) + offset;
> -}
> -
>  /**
>   * of_scan_flat_dt - scan flattened tree blob and call callback on each.
>   * @it: callback function
> @@ -123,38 +193,7 @@ unsigned long __init of_get_flat_dt_root(void)
>  void *__init of_get_flat_dt_prop(unsigned long node, const char *name,
>  				 unsigned long *size)
>  {
> -	unsigned long p = node;
> -
> -	do {
> -		u32 tag = be32_to_cpup((__be32 *)p);
> -		u32 sz, noff;
> -		const char *nstr;
> -
> -		p += 4;
> -		if (tag == OF_DT_NOP)
> -			continue;
> -		if (tag != OF_DT_PROP)
> -			return NULL;
> -
> -		sz = be32_to_cpup((__be32 *)p);
> -		noff = be32_to_cpup((__be32 *)(p + 4));
> -		p += 8;
> -		if (be32_to_cpu(initial_boot_params->version) < 0x10)
> -			p = ALIGN(p, sz >= 8 ? 8 : 4);
> -
> -		nstr = find_flat_dt_string(noff);
> -		if (nstr == NULL) {
> -			pr_warning("Can't find property index name !\n");
> -			return NULL;
> -		}
> -		if (strcmp(name, nstr) == 0) {
> -			if (size)
> -				*size = sz;
> -			return (void *)p;
> -		}
> -		p += sz;
> -		p = ALIGN(p, 4);
> -	} while (1);
> +	return of_fdt_get_property(initial_boot_params, node, name, size);
>  }
>  
>  /**
> @@ -164,21 +203,7 @@ void *__init of_get_flat_dt_prop(unsigned long node, const char *name,
>   */
>  int __init of_flat_dt_is_compatible(unsigned long node, const char *compat)
>  {
> -	const char *cp;
> -	unsigned long cplen, l;
> -
> -	cp = of_get_flat_dt_prop(node, "compatible", &cplen);
> -	if (cp == NULL)
> -		return 0;
> -	while (cplen > 0) {
> -		if (of_compat_cmp(cp, compat, strlen(compat)) == 0)
> -			return 1;
> -		l = strlen(cp) + 1;
> -		cp += l;
> -		cplen -= l;
> -	}
> -
> -	return 0;
> +	return of_fdt_is_compatible(initial_boot_params, node, compat);
>  }
>  
>  static void *__init unflatten_dt_alloc(unsigned long *mem, unsigned long size,
> @@ -303,7 +328,7 @@ unsigned long __init unflatten_dt_node(unsigned long mem,
>  		if (be32_to_cpu(initial_boot_params->version) < 0x10)
>  			*p = ALIGN(*p, sz >= 8 ? 8 : 4);
>  
> -		pname = find_flat_dt_string(noff);
> +		pname = of_fdt_get_string(initial_boot_params, noff);
>  		if (pname == NULL) {
>  			pr_info("Can't find property name in list !\n");
>  			break;
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index 7bbf5b3..70c5b73 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -58,6 +58,17 @@ struct boot_param_header {
>  };
>  
>  #if defined(CONFIG_OF_FLATTREE)
> +
> +/* For scanning an arbitrary device-tree at any time */
> +extern char *of_fdt_get_string(struct boot_param_header *blob, u32 offset);
> +extern void *of_fdt_get_property(struct boot_param_header *blob,
> +				 unsigned long node,
> +				 const char *name,
> +				 unsigned long *size);
> +extern int of_fdt_is_compatible(struct boot_param_header *blob,
> +				unsigned long node,
> +				const char *compat);
> +
>  /* TBD: Temporary export of fdt globals - remove when code fully merged */
>  extern int __initdata dt_root_addr_cells;
>  extern int __initdata dt_root_size_cells;
> -- 
> 1.5.6.6
> 
> 
> 
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