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    Subject[PATCH v2 1/5] dt: add of_alias_scan and of_alias_get_id
    Date
    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@linaro.org>
    Cc: Grant Likely <grant.likely@secretlab.ca>
    ---
    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
    + * @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;
    + }
    +}
    +
    +/**
    + * 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;
    + }
    +
    + 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--;
    +
    + 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)
    +{
    + 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;
    +}
    +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");
    +
    + 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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