Message-ID: <20110715025320.GE2927@ponder.secretlab.ca>
Date:	Thu, 14 Jul 2011 20:53:20 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Shawn Guo <shawn.guo@...aro.org>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-serial@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org, patches@...aro.org
Subject: Re: [PATCH v2 1/5] dt: add of_alias_scan and of_alias_get_id

On Sat, Jun 25, 2011 at 02:04:32AM +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@...aro.org>
> Cc: Grant Likely <grant.likely@...retlab.ca>

Hey Shawn,

Comments below, but I've gone ahead and fixed them because I'm keen to
get this patch merged.  I just wanted to let you know what I changed.
I'll post the modified version so you can test it.

> ---
>  drivers/of/base.c  |  181 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/fdt.c   |    6 ++
>  include/linux/of.h |    7 ++
>  3 files changed, 194 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 632ebae..89efd10 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -17,14 +17,38 @@
>   *      as published by the Free Software Foundation; either version
>   *      2 of the License, or (at your option) any later version.
>   */
> +#include <linux/bootmem.h>
> +#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
> + * @alias_id:	Alias id decoded from alias
> + * @alias_stem:	Alias stem name decoded from alias
> + *
> + * 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 alias_id;
> +	char alias_stem[0];
> +};
> +
> +static LIST_HEAD(aliases_lookup);
> +
>  struct device_node *allnodes;
>  struct device_node *of_chosen;
> +struct device_node *of_aliases;
>  
>  /* use when traversing tree through the allnext, child, sibling,
>   * or parent members of struct device_node.
> @@ -922,3 +946,160 @@ out_unlock:
>  }
>  #endif /* defined(CONFIG_OF_DYNAMIC) */
>  
> +/*
> + * of_alias_find_available_id - Find an available id for the given device_node

Nit: kerneldoc format is "/**" to start the comment, and function
names should have '()' on it.

> + * @np:		Pointer to the given device_node
> + * @stem:	Alias stem of the given device_node
> + *
> + * The function travels the lookup table to find an available id for the
> + * given device_node with given alias stem.  It returns the id found.
> + */
> +static int of_alias_find_available_id(struct device_node *np, const char *stem)
> +{
> +	struct alias_prop *app;
> +	int id = 0;
> +
> +	while (1) {
> +		bool used = false;
> +		list_for_each_entry(app, &aliases_lookup, link) {
> +			if (!strcmp(app->alias_stem, stem) &&
> +			    app->alias_id == id) {
> +				used = true;
> +				break;
> +			}
> +		}
> +
> +		if (used)
> +			id++;
> +		else
> +			return id;
> +	}
> +}

I've simplified this somewhat to do the list_for_each_entry() only
once, and to bump up the id to +1 the largest entry:

	list_for_each_entry(app, &aliases_lookup, link)
		if ((strcmp(app->stem, stem) == 0) && id <= app->id)
			id = app->id + 1;

.... actually, after looking further, I've rolled this code into the
of_alias_get_id() function.

> +
> +/**
> + * of_alias_lookup_add - Add alias into lookup table
> + * @alias:	Alias name
> + * @id:		Alias id
> + * @stem:	Alias stem name
> + * @np:		Pointer to device_node
> + *
> + * The function adds one alias into the lookup table and populate it
> + * with the info passed in.  It returns 0 in sucess, or error code.
> + */
> +static int of_alias_lookup_add(char *alias, int id, const char *stem,
> +			       struct device_node *np)
> +{
> +	struct alias_prop *app;
> +	size_t sz = sizeof(*app) + strlen(stem) + 1;
> +
> +	app = kzalloc(sz, GFP_KERNEL);
> +	if (!app) {
> +		/*
> +		 * It may fail due to being called by boot code,
> +		 * so try alloc_bootmem before return error.
> +		 */
> +		app = alloc_bootmem(sz);
> +		if (!app)
> +			return -ENOMEM;
> +	}

I'm not too fond of this since we *know* when this is going to be
called from early boot.  So, instead, I've changed the code to use the
already existing dt_alloc functions as an argument to of_alias_lookup_add().

Also, alloc_bootmem() doesn't work on all platforms.
early_init_dt_alloc_memory_arch() needs to be used instead.


> +
> +	app->np = np;
> +	app->alias = alias;
> +	app->alias_id = id;
> +	strcpy(app->alias_stem, stem);
> +	list_add_tail(&app->link, &aliases_lookup);
> +
> +	return 0;
> +}
> +
> +/**
> + * of_alias_decode - Decode alias stem and id from alias name
> + * @alias:	Alias name to be decoded
> + * @stem:	Pointer used to return stem name
> + *
> + * The function decodes alias stem name and alias id from the given
> + * alias name.  It returns stem name via parameter 'stem', and stem id
> + * via the return value.  If no id is found in alias name, it returns 0
> + * as the default.
> + */
> +static int of_alias_decode(char *alias, char *stem)
> +{
> +	int len = strlen(alias);
> +	char *end = alias + len;
> +
> +	while (isdigit(*--end))
> +		len--;

Need to protect against len < 0

> +
> +	strncpy(stem, alias, len);
> +	stem[len] = '\0';
> +
> +	return strlen(++end) ? simple_strtoul(end, NULL, 10) : 0;
> +}
> +
> +/**
> + * 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.
> + */
> +int of_alias_scan(void)

Changed to '__init void of_aliases_scan(void)'.  There is no point in
returning an error code since it is never checked, and there is no
point in bailing on an error just in case it is a problem with only
one alias.

> +{
> +	struct property *pp;
> +	int ret, num = 0;
> +
> +	if (!of_aliases)
> +		return -ENODEV;
> +
> +	for_each_property(pp, of_aliases->properties) {
> +		char stem[32];
> +		int id = of_alias_decode(pp->name, stem);
> +
> +		/* Skip those we do not want to proceed */
> +		if (!strcmp(pp->name, "name") ||
> +		    !strcmp(pp->name, "phandle") ||
> +		    !strcmp(pp->name, "linux,phandle"))
> +			continue;
> +
> +		ret = of_alias_lookup_add(pp->name, id, stem,
> +					  of_find_node_by_path(pp->value));
> +		if (ret < 0)
> +			return ret;
> +		else
> +			num++;
> +	}
> +
> +	return num;
> +}
> +
> +/**
> + * 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 = -1;
> +
> +	list_for_each_entry(app, &aliases_lookup, link) {
> +		if (np == app->np) {
> +			id = app->alias_id;
> +			break;
> +		}
> +	}
> +
> +	if (id == -1) {
> +		id = of_alias_find_available_id(np, stem);
> +		if (of_alias_lookup_add(NULL, id, stem, np) < 0)
> +			return -ENODEV;
> +	}
> +
> +	return id;
> +}

This whole function needs to be protected by a mutex.

> +EXPORT_SYMBOL_GPL(of_alias_get_id);
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 65200af..998dc63 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -711,6 +711,12 @@ void __init unflatten_device_tree(void)
>  	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");
> +	if (of_aliases == NULL)
> +		of_aliases = of_find_node_by_path("/aliases@0");

I don't think the /aliases@0 variant is necessary.  I've dropped it.

g.

> +
> +	of_alias_scan();
>  }
>  
>  #endif /* CONFIG_OF_EARLY_FLATTREE */
> diff --git a/include/linux/of.h b/include/linux/of.h
> index bfc0ed1..c35cc47 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)
> @@ -201,6 +202,9 @@ 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(
> @@ -213,6 +217,9 @@ 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 int of_alias_scan(void);
> +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);
> -- 
> 1.7.4.1
> 
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