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component: add support for releasing match data
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The component helper treats the void match data pointer as an opaque
object which needs no further management.  When device nodes being
passed, this is not true: the caller should pass its refcount to the
component helper, and there should be a way to drop the refcount when
the matching information is destroyed.

This patch provides a per-match release method in addition to the match
method to solve this issue.  Rather than using component_match_add(),
users should use component_match_add_release() which takes an additional
function pointer for releasing this reference.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King committed Dec 7, 2015
1 parent ffc30b7 commit ce657b1
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Showing 2 changed files with 87 additions and 42 deletions.
101 changes: 66 additions & 35 deletions drivers/base/component.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -20,15 +20,18 @@

struct component;

struct component_match_array {
void *data;
int (*compare)(struct device *, void *);
void (*release)(struct device *, void *);
struct component *component;
bool duplicate;
};

struct component_match {
size_t alloc;
size_t num;
struct {
void *data;
int (*fn)(struct device *, void *);
struct component *component;
bool duplicate;
} compare[0];
struct component_match_array *compare;
};

struct master {
Expand Down Expand Up @@ -92,15 +95,15 @@ static int find_components(struct master *master)
* any components which are found to this master.
*/
for (i = 0; i < match->num; i++) {
struct component_match_array *mc = &match->compare[i];
struct component *c;

dev_dbg(master->dev, "Looking for component %zu\n", i);

if (match->compare[i].component)
continue;

c = find_component(master, match->compare[i].fn,
match->compare[i].data);
c = find_component(master, mc->compare, mc->data);
if (!c) {
ret = -ENXIO;
break;
Expand Down Expand Up @@ -192,65 +195,93 @@ static void take_down_master(struct master *master)
}
}

static size_t component_match_size(size_t num)
static void component_match_release(struct device *master,
struct component_match *match)
{
unsigned int i;

for (i = 0; i < match->num; i++) {
struct component_match_array *mc = &match->compare[i];

if (mc->release)
mc->release(master, mc->data);
}
}

static void devm_component_match_release(struct device *dev, void *res)
{
return offsetof(struct component_match, compare[num]);
component_match_release(dev, res);
}

static struct component_match *component_match_realloc(struct device *dev,
static int component_match_realloc(struct device *dev,
struct component_match *match, size_t num)
{
struct component_match *new;
struct component_match_array *new;

if (match && match->alloc == num)
return match;
if (match->alloc == num)
return 0;

new = devm_kmalloc(dev, component_match_size(num), GFP_KERNEL);
new = devm_kmalloc_array(dev, num, sizeof(*new), GFP_KERNEL);
if (!new)
return ERR_PTR(-ENOMEM);
return -ENOMEM;

if (match) {
memcpy(new, match, component_match_size(min(match->num, num)));
devm_kfree(dev, match);
} else {
new->num = 0;
if (match->compare) {
memcpy(new, match->compare, sizeof(*new) *
min(match->num, num));
devm_kfree(dev, match->compare);
}
match->compare = new;
match->alloc = num;

new->alloc = num;

return new;
return 0;
}

/*
* Add a component to be matched.
* Add a component to be matched, with a release function.
*
* The match array is first created or extended if necessary.
*/
void component_match_add(struct device *dev, struct component_match **matchptr,
void component_match_add_release(struct device *master,
struct component_match **matchptr,
void (*release)(struct device *, void *),
int (*compare)(struct device *, void *), void *compare_data)
{
struct component_match *match = *matchptr;

if (IS_ERR(match))
return;

if (!match || match->num == match->alloc) {
size_t new_size = match ? match->alloc + 16 : 15;
if (!match) {
match = devres_alloc(devm_component_match_release,
sizeof(*match), GFP_KERNEL);
if (!match) {
*matchptr = ERR_PTR(-ENOMEM);
return;
}

match = component_match_realloc(dev, match, new_size);
devres_add(master, match);

*matchptr = match;
}

if (match->num == match->alloc) {
size_t new_size = match ? match->alloc + 16 : 15;
int ret;

if (IS_ERR(match))
ret = component_match_realloc(master, match, new_size);
if (ret) {
*matchptr = ERR_PTR(ret);
return;
}
}

match->compare[match->num].fn = compare;
match->compare[match->num].compare = compare;
match->compare[match->num].release = release;
match->compare[match->num].data = compare_data;
match->compare[match->num].component = NULL;
match->num++;
}
EXPORT_SYMBOL(component_match_add);
EXPORT_SYMBOL(component_match_add_release);

int component_master_add_with_match(struct device *dev,
const struct component_master_ops *ops,
Expand All @@ -260,9 +291,9 @@ int component_master_add_with_match(struct device *dev,
int ret;

/* Reallocate the match array for its true size */
match = component_match_realloc(dev, match, match->num);
if (IS_ERR(match))
return PTR_ERR(match);
ret = component_match_realloc(dev, match, match->num);
if (ret)
return ret;

master = kzalloc(sizeof(*master), GFP_KERNEL);
if (!master)
Expand Down
28 changes: 21 additions & 7 deletions include/linux/component.h
View file
Original file line number Diff line number Diff line change
@@ -1,24 +1,28 @@
#ifndef COMPONENT_H
#define COMPONENT_H

#include <linux/stddef.h>

struct device;

struct component_ops {
int (*bind)(struct device *, struct device *, void *);
void (*unbind)(struct device *, struct device *, void *);
int (*bind)(struct device *comp, struct device *master,
void *master_data);
void (*unbind)(struct device *comp, struct device *master,
void *master_data);
};

int component_add(struct device *, const struct component_ops *);
void component_del(struct device *, const struct component_ops *);

int component_bind_all(struct device *, void *);
void component_unbind_all(struct device *, void *);
int component_bind_all(struct device *master, void *master_data);
void component_unbind_all(struct device *master, void *master_data);

struct master;

struct component_master_ops {
int (*bind)(struct device *);
void (*unbind)(struct device *);
int (*bind)(struct device *master);
void (*unbind)(struct device *master);
};

void component_master_del(struct device *,
Expand All @@ -28,7 +32,17 @@ struct component_match;

int component_master_add_with_match(struct device *,
const struct component_master_ops *, struct component_match *);
void component_match_add(struct device *, struct component_match **,
void component_match_add_release(struct device *master,
struct component_match **matchptr,
void (*release)(struct device *, void *),
int (*compare)(struct device *, void *), void *compare_data);

static inline void component_match_add(struct device *master,
struct component_match **matchptr,
int (*compare)(struct device *, void *), void *compare_data)
{
component_match_add_release(master, matchptr, NULL, compare,
compare_data);
}

#endif

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