Re: [PATCH v2] dt: add of_alias_scan and of_alias_get_id

[Grant Likely]

On Mon, Aug 15, 2011 at 03:28:14PM +0800, Shawn Guo wrote:
> The patch adds function of_alias_scan to populate a global lookup
> table with the properties of 'aliases' node and function
> of_alias_get_id for drivers to find alias id from the lookup table.
> 
> Signed-off-by: Shawn Guo <shawn.guo@xxxxxxxxxx>
> [grant.likey: add locking and rework parse loop]
> Signed-off-by: Grant Likely <grant.likely@xxxxxxxxxxxx>
> ---
> Changes since v1:
>  * Add of_chosen/of_aliases populating and of_alias_scan() invocation
>    for OF_PROMTREE (non-tested).

Hi Shawn,

It's taken me a very long time to get some bandwidth to look at this
patch.  I do have some minor comments, but rather than waiting for a
respin and delaying even further, I'm picking up the bits that are
are ready to go so that the remaining part (auto allocating of unused
ids) can be debated without holding things up.

> 
>  drivers/of/base.c      |  136 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/fdt.c       |   12 +++--
>  drivers/of/pdt.c       |   12 ++++
>  include/linux/of.h     |    8 +++
>  include/linux/of_fdt.h |    1 -
>  5 files changed, 163 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 3ff22e3..5e6ce02 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -17,14 +17,39 @@
>   *      as published by the Free Software Foundation; either version
>   *      2 of the License, or (at your option) any later version.
>   */
> +#include <linux/ctype.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
>  #include <linux/proc_fs.h>
>  
> +/**
> + * struct alias_prop - Alias property in 'aliases' node
> + * @link:	List node to link the structure in aliases_lookup list
> + * @alias:	Alias property name
> + * @np:		Pointer to device_node that the alias stands for
> + * @id:		Index value from end of alias name
> + * @stem:	Alias string without the index
> + *
> + * The structure represents one alias property of 'aliases' node as
> + * an entry in aliases_lookup list.
> + */
> +struct alias_prop {
> +	struct list_head link;
> +	const char *alias;
> +	struct device_node *np;
> +	int id;
> +	char stem[0];
> +};
> +
> +static LIST_HEAD(aliases_lookup);
> +
>  struct device_node *allnodes;
>  struct device_node *of_chosen;
> +struct device_node *of_aliases;
> +
> +static DEFINE_MUTEX(of_aliases_mutex);
>  
>  /* use when traversing tree through the allnext, child, sibling,
>   * or parent members of struct device_node.
> @@ -988,3 +1013,114 @@ out_unlock:
>  }
>  #endif /* defined(CONFIG_OF_DYNAMIC) */
>  
> +static void of_alias_add(struct alias_prop *ap, struct device_node *np,
> +			 int id, const char *stem, int stem_len)
> +{
> +	ap->np = np;
> +	ap->id = id;
> +	strncpy(ap->stem, stem, stem_len);
> +	ap->stem[stem_len] = 0;
> +	list_add_tail(&ap->link, &aliases_lookup);
> +	pr_debug("adding DT alias:%s: stem=%s id=%i node=%s\n",
> +		 ap->alias, ap->stem, ap->id, np ? np->full_name : NULL);
> +}
> +
> +/**
> + * of_alias_scan - Scan all properties of 'aliases' node
> + *
> + * The function scans all the properties of 'aliases' node and populate
> + * the the global lookup table with the properties.  It returns the
> + * number of alias_prop found, or error code in error case.
> + *
> + * @dt_alloc:	An allocator that provides a virtual address to memory
> + *		for the resulting tree
> + */
> +void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
> +{
> +	struct property *pp;
> +
> +	if (!of_aliases)
> +		return;
> +
> +	for_each_property(pp, of_aliases->properties) {
> +		const char *start = pp->name;
> +		const char *end = start + strlen(start);
> +		struct device_node *np;
> +		struct alias_prop *ap;
> +		int id, len;
> +
> +		/* Skip those we do not want to proceed */
> +		if (!strcmp(pp->name, "name") ||
> +		    !strcmp(pp->name, "phandle") ||
> +		    !strcmp(pp->name, "linux,phandle"))
> +			continue;
> +
> +		np = of_find_node_by_path(pp->value);
> +		if (!np)
> +			continue;
> +
> +		/* walk the alias backwards to extract the id and work out
> +		 * the 'stem' string */
> +		while (isdigit(*(end-1)) && end > start)
> +			end--;
> +		len = end - start;
> +
> +		if (kstrtoint(end, 10, &id) < 0)
> +			continue;
> +
> +		/* Allocate an alias_prop with enough space for the stem */
> +		ap = dt_alloc(sizeof(*ap) + len + 1, 4);
> +		if (!ap)
> +			continue;
> +		ap->alias = start;
> +		of_alias_add(ap, np, id, start, len);
> +	}
> +}
> +
> +/**
> + * of_alias_get_id - Get alias id for the given device_node
> + * @np:		Pointer to the given device_node
> + * @stem:	Alias stem of the given device_node
> + *
> + * The function travels the lookup table to get alias id for the given
> + * device_node and alias stem.  It returns the alias id if find it.
> + * If not, dynamically creates one in the lookup table and returns it,
> + * or returns error code if fail to create.
> + */
> +int of_alias_get_id(struct device_node *np, const char *stem)
> +{
> +	struct alias_prop *app;
> +	int id = 0;
> +	bool found = false;
> +
> +	mutex_lock(&of_aliases_mutex);
> +	list_for_each_entry(app, &aliases_lookup, link) {
> +		if (strcmp(app->stem, stem) != 0)
> +			continue;
> +
> +		if (np == app->np) {
> +			found = true;
> +			id = app->id;
> +			break;
> +		}
> +
> +		if (id <= app->id)
> +			id = app->id + 1;
> +	}
> +
> +	/* If an id is not found, then allocate a new one */
> +	if (!found) {
> +		app = kzalloc(sizeof(*app) + strlen(stem) + 1, 4);
> +		if (!app) {
> +			id = -ENODEV;
> +			goto out;
> +		}
> +		of_alias_add(app, np, id, stem, strlen(stem));
> +	}

This was the controversial bit last time around.  I'm dropping this
block from the patch because the core aliases scanning is still
important.  The allocating of new ids can be debated separately.

> +
> + out:
> +	mutex_unlock(&of_aliases_mutex);
> +
> +	return id;
> +}
> +EXPORT_SYMBOL_GPL(of_alias_get_id);
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 65200af..98b6fb1 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -404,6 +404,13 @@ static void __unflatten_device_tree(struct boot_param_header *blob,
>  			   be32_to_cpu(((__be32 *)mem)[size / 4]));
>  	*allnextp = NULL;
>  
> +	/* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
> +	of_chosen = of_find_node_by_path("/chosen");
> +	if (of_chosen == NULL)
> +		of_chosen = of_find_node_by_path("/chosen@0");
> +	of_aliases = of_find_node_by_path("/aliases");
> +	of_alias_scan(dt_alloc);
> +
>  	pr_debug(" <- unflatten_device_tree()\n");
>  }
>  
> @@ -706,11 +713,6 @@ void __init unflatten_device_tree(void)
>  {
>  	__unflatten_device_tree(initial_boot_params, &allnodes,
>  				early_init_dt_alloc_memory_arch);
> -
> -	/* Get pointer to OF "/chosen" node for use everywhere */
> -	of_chosen = of_find_node_by_path("/chosen");
> -	if (of_chosen == NULL)
> -		of_chosen = of_find_node_by_path("/chosen@0");

Don't move this hunk.  There are callers of __unflatten_device_tree,
such as when processing device tree fragments, which do not want to
proceses /chosen or /aliases.  I've moved it back to where it started
from.

>  }
>  
>  #endif /* CONFIG_OF_EARLY_FLATTREE */
> diff --git a/drivers/of/pdt.c b/drivers/of/pdt.c
> index 4d87b5d..686a4b3 100644
> --- a/drivers/of/pdt.c
> +++ b/drivers/of/pdt.c
> @@ -229,6 +229,11 @@ static struct device_node * __init of_pdt_build_tree(struct device_node *parent,
>  	return ret;
>  }
>  
> +static void *kernel_tree_alloc(u64 size, u64 align)
> +{
> +	return prom_early_alloc(size);
> +}
> +
>  void __init of_pdt_build_devicetree(phandle root_node, struct of_pdt_ops *ops)
>  {
>  	struct device_node **nextp;
> @@ -245,4 +250,11 @@ void __init of_pdt_build_devicetree(phandle root_node, struct of_pdt_ops *ops)
>  	nextp = &allnodes->allnext;
>  	allnodes->child = of_pdt_build_tree(allnodes,
>  			of_pdt_prom_ops->getchild(allnodes->phandle), &nextp);
> +
> +	/* Get pointer to "/chosen" and "/aliasas" nodes for use everywhere */
> +	of_chosen = of_find_node_by_path("/chosen");
> +	if (of_chosen == NULL)
> +		of_chosen = of_find_node_by_path("/chosen@0");
> +	of_aliases = of_find_node_by_path("/aliases");
> +	of_alias_scan(kernel_tree_alloc);

Thinking about it more, there is no need to have the
of_find_node_by_path() outside of of_alias_scan().  I've moved it.  In
fact, I think I'll move the /chosen search into of_alias_scan() too.

>  }
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 9180dc5..4ea7d81 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -68,6 +68,7 @@ struct device_node {
>  /* Pointer for first entry in chain of all nodes. */
>  extern struct device_node *allnodes;
>  extern struct device_node *of_chosen;
> +extern struct device_node *of_aliases;
>  extern rwlock_t devtree_lock;
>  
>  static inline bool of_have_populated_dt(void)
> @@ -209,6 +210,9 @@ extern int of_device_is_available(const struct device_node *device);
>  extern const void *of_get_property(const struct device_node *node,
>  				const char *name,
>  				int *lenp);
> +#define for_each_property(pp, properties) \
> +	for (pp = properties; pp != NULL; pp = pp->next)
> +
>  extern int of_n_addr_cells(struct device_node *np);
>  extern int of_n_size_cells(struct device_node *np);
>  extern const struct of_device_id *of_match_node(
> @@ -221,6 +225,10 @@ extern int of_parse_phandles_with_args(struct device_node *np,
>  	const char *list_name, const char *cells_name, int index,
>  	struct device_node **out_node, const void **out_args);
>  
> +extern void *early_init_dt_alloc_memory_arch(u64 size, u64 align);
> +extern void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align));
> +extern int of_alias_get_id(struct device_node *np, const char *stem);
> +
>  extern int of_machine_is_compatible(const char *compat);
>  
>  extern int prom_add_property(struct device_node* np, struct property* prop);
> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> index c84d900..b74b74f 100644
> --- a/include/linux/of_fdt.h
> +++ b/include/linux/of_fdt.h
> @@ -97,7 +97,6 @@ extern void early_init_dt_check_for_initrd(unsigned long node);
>  extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
>  				     int depth, void *data);
>  extern void early_init_dt_add_memory_arch(u64 base, u64 size);
> -extern void * early_init_dt_alloc_memory_arch(u64 size, u64 align);

This prototype doesn't need to move.  I've moved it back.

Otherwise looks good.  I'll post a v3 showing the version that I'm
merging.

g.

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