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Message-ID: <20110715152449.GF1840@S2100-06.ap.freescale.net>
Date: Fri, 15 Jul 2011 23:24:50 +0800
From: Shawn Guo <shawn.guo@...escale.com>
To: Grant Likely <grant.likely@...retlab.ca>
CC: Shawn Guo <shawn.guo@...aro.org>,
<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 Thu, Jul 14, 2011 at 08:53:20PM -0600, Grant Likely wrote:
> 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.
>
Thanks for doing this. It makes the wheel spin fast. I respect
changes you made, and will give it a test once you post it.
Regards,
Shawn
> > ---
> > 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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