Commit 9ac7849e authored by Tejun Heo's avatar Tejun Heo Committed by Jeff Garzik

devres: device resource management

Implement device resource management, in short, devres.  A device
driver can allocate arbirary size of devres data which is associated
with a release function.  On driver detach, release function is
invoked on the devres data, then, devres data is freed.

devreses are typed by associated release functions.  Some devreses are
better represented by single instance of the type while others need
multiple instances sharing the same release function.  Both usages are
supported.

devreses can be grouped using devres group such that a device driver
can easily release acquired resources halfway through initialization
or selectively release resources (e.g. resources for port 1 out of 4
ports).

This patch adds devres core including documentation and the following
managed interfaces.

* alloc/free	: devm_kzalloc(), devm_kzfree()
* IO region	: devm_request_region(), devm_release_region()
* IRQ		: devm_request_irq(), devm_free_irq()
* DMA		: dmam_alloc_coherent(), dmam_free_coherent(),
		  dmam_declare_coherent_memory(), dmam_pool_create(),
		  dmam_pool_destroy()
* PCI		: pcim_enable_device(), pcim_pin_device(), pci_is_managed()
* iomap		: devm_ioport_map(), devm_ioport_unmap(), devm_ioremap(),
		  devm_ioremap_nocache(), devm_iounmap(), pcim_iomap_table(),
		  pcim_iomap(), pcim_iounmap()
Signed-off-by: default avatarTejun Heo <htejun@gmail.com>
Signed-off-by: default avatarJeff Garzik <jeff@garzik.org>
parent 77a527ea
Devres - Managed Device Resource
================================
Tejun Heo <teheo@suse.de>
First draft 10 January 2007
1. Intro : Huh? Devres?
2. Devres : Devres in a nutshell
3. Devres Group : Group devres'es and release them together
4. Details : Life time rules, calling context, ...
5. Overhead : How much do we have to pay for this?
6. List of managed interfaces : Currently implemented managed interfaces
1. Intro
--------
devres came up while trying to convert libata to use iomap. Each
iomapped address should be kept and unmapped on driver detach. For
example, a plain SFF ATA controller (that is, good old PCI IDE) in
native mode makes use of 5 PCI BARs and all of them should be
maintained.
As with many other device drivers, libata low level drivers have
sufficient bugs in ->remove and ->probe failure path. Well, yes,
that's probably because libata low level driver developers are lazy
bunch, but aren't all low level driver developers? After spending a
day fiddling with braindamaged hardware with no document or
braindamaged document, if it's finally working, well, it's working.
For one reason or another, low level drivers don't receive as much
attention or testing as core code, and bugs on driver detach or
initilaization failure doesn't happen often enough to be noticeable.
Init failure path is worse because it's much less travelled while
needs to handle multiple entry points.
So, many low level drivers end up leaking resources on driver detach
and having half broken failure path implementation in ->probe() which
would leak resources or even cause oops when failure occurs. iomap
adds more to this mix. So do msi and msix.
2. Devres
---------
devres is basically linked list of arbitrarily sized memory areas
associated with a struct device. Each devres entry is associated with
a release function. A devres can be released in several ways. No
matter what, all devres entries are released on driver detach. On
release, the associated release function is invoked and then the
devres entry is freed.
Managed interface is created for resources commonly used by device
drivers using devres. For example, coherent DMA memory is acquired
using dma_alloc_coherent(). The managed version is called
dmam_alloc_coherent(). It is identical to dma_alloc_coherent() except
for the DMA memory allocated using it is managed and will be
automatically released on driver detach. Implementation looks like
the following.
struct dma_devres {
size_t size;
void *vaddr;
dma_addr_t dma_handle;
};
static void dmam_coherent_release(struct device *dev, void *res)
{
struct dma_devres *this = res;
dma_free_coherent(dev, this->size, this->vaddr, this->dma_handle);
}
dmam_alloc_coherent(dev, size, dma_handle, gfp)
{
struct dma_devres *dr;
void *vaddr;
dr = devres_alloc(dmam_coherent_release, sizeof(*dr), gfp);
...
/* alloc DMA memory as usual */
vaddr = dma_alloc_coherent(...);
...
/* record size, vaddr, dma_handle in dr */
dr->vaddr = vaddr;
...
devres_add(dev, dr);
return vaddr;
}
If a driver uses dmam_alloc_coherent(), the area is guaranteed to be
freed whether initialization fails half-way or the device gets
detached. If most resources are acquired using managed interface, a
driver can have much simpler init and exit code. Init path basically
looks like the following.
my_init_one()
{
struct mydev *d;
d = devm_kzalloc(dev, sizeof(*d), GFP_KERNEL);
if (!d)
return -ENOMEM;
d->ring = dmam_alloc_coherent(...);
if (!d->ring)
return -ENOMEM;
if (check something)
return -EINVAL;
...
return register_to_upper_layer(d);
}
And exit path,
my_remove_one()
{
unregister_from_upper_layer(d);
shutdown_my_hardware();
}
As shown above, low level drivers can be simplified a lot by using
devres. Complexity is shifted from less maintained low level drivers
to better maintained higher layer. Also, as init failure path is
shared with exit path, both can get more testing.
3. Devres group
---------------
Devres entries can be grouped using devres group. When a group is
released, all contained normal devres entries and properly nested
groups are released. One usage is to rollback series of acquired
resources on failure. For example,
if (!devres_open_group(dev, NULL, GFP_KERNEL))
return -ENOMEM;
acquire A;
if (failed)
goto err;
acquire B;
if (failed)
goto err;
...
devres_remove_group(dev, NULL);
return 0;
err:
devres_release_group(dev, NULL);
return err_code;
As resource acquision failure usually means probe failure, constructs
like above are usually useful in midlayer driver (e.g. libata core
layer) where interface function shouldn't have side effect on failure.
For LLDs, just returning error code suffices in most cases.
Each group is identified by void *id. It can either be explicitly
specified by @id argument to devres_open_group() or automatically
created by passing NULL as @id as in the above example. In both
cases, devres_open_group() returns the group's id. The returned id
can be passed to other devres functions to select the target group.
If NULL is given to those functions, the latest open group is
selected.
For example, you can do something like the following.
int my_midlayer_create_something()
{
if (!devres_open_group(dev, my_midlayer_create_something, GFP_KERNEL))
return -ENOMEM;
...
devres_close_group(dev, my_midlayer_something);
return 0;
}
void my_midlayer_destroy_something()
{
devres_release_group(dev, my_midlayer_create_soemthing);
}
4. Details
----------
Lifetime of a devres entry begins on devres allocation and finishes
when it is released or destroyed (removed and freed) - no reference
counting.
devres core guarantees atomicity to all basic devres operations and
has support for single-instance devres types (atomic
lookup-and-add-if-not-found). Other than that, synchronizing
concurrent accesses to allocated devres data is caller's
responsibility. This is usually non-issue because bus ops and
resource allocations already do the job.
For an example of single-instance devres type, read pcim_iomap_table()
in lib/iomap.c.
All devres interface functions can be called without context if the
right gfp mask is given.
5. Overhead
-----------
Each devres bookkeeping info is allocated together with requested data
area. With debug option turned off, bookkeeping info occupies 16
bytes on 32bit machines and 24 bytes on 64bit (three pointers rounded
up to ull alignment). If singly linked list is used, it can be
reduced to two pointers (8 bytes on 32bit, 16 bytes on 64bit).
Each devres group occupies 8 pointers. It can be reduced to 6 if
singly linked list is used.
Memory space overhead on ahci controller with two ports is between 300
and 400 bytes on 32bit machine after naive conversion (we can
certainly invest a bit more effort into libata core layer).
6. List of managed interfaces
-----------------------------
IO region
devm_request_region()
devm_request_mem_region()
devm_release_region()
devm_release_mem_region()
IRQ
devm_request_irq()
devm_free_irq()
DMA
dmam_alloc_coherent()
dmam_free_coherent()
dmam_alloc_noncoherent()
dmam_free_noncoherent()
dmam_declare_coherent_memory()
dmam_pool_create()
dmam_pool_destroy()
PCI
pcim_enable_device() : after success, all PCI ops become managed
pcim_pin_device() : keep PCI device enabled after release
IOMAP
devm_ioport_map()
devm_ioport_unmap()
devm_ioremap()
devm_ioremap_nocache()
devm_iounmap()
pcim_iomap()
pcim_iounmap()
pcim_iomap_table() : array of mapped addresses indexed by BAR
pcim_iomap_regions() : do request_region() and iomap() on multiple BARs
......@@ -37,6 +37,18 @@ config DEBUG_DRIVER
If you are unsure about this, say N here.
config DEBUG_DEVRES
bool "Managed device resources verbose debug messages"
depends on DEBUG_KERNEL
help
This option enables kernel parameter devres.log. If set to
non-zero, devres debug messages are printed. Select this if
you are having a problem with devres or want to debug
resource management for a managed device. devres.log can be
switched on and off from sysfs node.
If you are unsure about this, Say N here.
config SYS_HYPERVISOR
bool
default n
......
......@@ -3,6 +3,7 @@
obj-y := core.o sys.o bus.o dd.o \
driver.o class.o platform.o \
cpu.o firmware.o init.o map.o dmapool.o \
dma-mapping.o devres.o \
attribute_container.o transport_class.o
obj-y += power/
obj-$(CONFIG_ISA) += isa.o
......
......@@ -44,3 +44,4 @@ struct class_device_attribute *to_class_dev_attr(struct attribute *_attr)
extern char *make_class_name(const char *name, struct kobject *kobj);
extern void devres_release_all(struct device *dev);
......@@ -428,6 +428,8 @@ void device_initialize(struct device *dev)
INIT_LIST_HEAD(&dev->dma_pools);
INIT_LIST_HEAD(&dev->node);
init_MUTEX(&dev->sem);
spin_lock_init(&dev->devres_lock);
INIT_LIST_HEAD(&dev->devres_head);
device_init_wakeup(dev, 0);
set_dev_node(dev, -1);
}
......
......@@ -112,6 +112,7 @@ static int really_probe(void *void_data)
atomic_inc(&probe_count);
pr_debug("%s: Probing driver %s with device %s\n",
drv->bus->name, drv->name, dev->bus_id);
WARN_ON(!list_empty(&dev->devres_head));
dev->driver = drv;
if (driver_sysfs_add(dev)) {
......@@ -137,6 +138,7 @@ static int really_probe(void *void_data)
goto done;
probe_failed:
devres_release_all(dev);
driver_sysfs_remove(dev);
dev->driver = NULL;
......@@ -327,6 +329,7 @@ static void __device_release_driver(struct device * dev)
dev->bus->remove(dev);
else if (drv->remove)
drv->remove(dev);
devres_release_all(dev);
dev->driver = NULL;
put_driver(drv);
}
......
/*
* drivers/base/devres.c - device resource management
*
* Copyright (c) 2006 SUSE Linux Products GmbH
* Copyright (c) 2006 Tejun Heo <teheo@suse.de>
*
* This file is released under the GPLv2.
*/
#include <linux/device.h>
#include <linux/module.h>
struct devres_node {
struct list_head entry;
dr_release_t release;
#ifdef CONFIG_DEBUG_DEVRES
const char *name;
size_t size;
#endif
};
struct devres {
struct devres_node node;
/* -- 3 pointers */
unsigned long long data[]; /* guarantee ull alignment */
};
struct devres_group {
struct devres_node node[2];
void *id;
int color;
/* -- 8 pointers */
};
#ifdef CONFIG_DEBUG_DEVRES
static int log_devres = 0;
module_param_named(log, log_devres, int, S_IRUGO | S_IWUSR);
static void set_node_dbginfo(struct devres_node *node, const char *name,
size_t size)
{
node->name = name;
node->size = size;
}
static void devres_log(struct device *dev, struct devres_node *node,
const char *op)
{
if (unlikely(log_devres))
dev_printk(KERN_ERR, dev, "DEVRES %3s %p %s (%lu bytes)\n",
op, node, node->name, (unsigned long)node->size);
}
#else /* CONFIG_DEBUG_DEVRES */
#define set_node_dbginfo(node, n, s) do {} while (0)
#define devres_log(dev, node, op) do {} while (0)
#endif /* CONFIG_DEBUG_DEVRES */
/*
* Release functions for devres group. These callbacks are used only
* for identification.
*/
static void group_open_release(struct device *dev, void *res)
{
/* noop */
}
static void group_close_release(struct device *dev, void *res)
{
/* noop */
}
static struct devres_group * node_to_group(struct devres_node *node)
{
if (node->release == &group_open_release)
return container_of(node, struct devres_group, node[0]);
if (node->release == &group_close_release)
return container_of(node, struct devres_group, node[1]);
return NULL;
}
static __always_inline struct devres * alloc_dr(dr_release_t release,
size_t size, gfp_t gfp)
{
size_t tot_size = sizeof(struct devres) + size;
struct devres *dr;
dr = kmalloc_track_caller(tot_size, gfp);
if (unlikely(!dr))
return NULL;
memset(dr, 0, tot_size);
INIT_LIST_HEAD(&dr->node.entry);
dr->node.release = release;
return dr;
}
static void add_dr(struct device *dev, struct devres_node *node)
{
devres_log(dev, node, "ADD");
BUG_ON(!list_empty(&node->entry));
list_add_tail(&node->entry, &dev->devres_head);
}
/**
* devres_alloc - Allocate device resource data
* @release: Release function devres will be associated with
* @size: Allocation size
* @gfp: Allocation flags
*
* allocate devres of @size bytes. The allocated area is zeroed, then
* associated with @release. The returned pointer can be passed to
* other devres_*() functions.
*
* RETURNS:
* Pointer to allocated devres on success, NULL on failure.
*/
#ifdef CONFIG_DEBUG_DEVRES
void * __devres_alloc(dr_release_t release, size_t size, gfp_t gfp,
const char *name)
{
struct devres *dr;
dr = alloc_dr(release, size, gfp);
if (unlikely(!dr))
return NULL;
set_node_dbginfo(&dr->node, name, size);
return dr->data;
}
EXPORT_SYMBOL_GPL(__devres_alloc);
#else
void * devres_alloc(dr_release_t release, size_t size, gfp_t gfp)
{
struct devres *dr;
dr = alloc_dr(release, size, gfp);
if (unlikely(!dr))
return NULL;
return dr->data;
}
EXPORT_SYMBOL_GPL(devres_alloc);
#endif
/**
* devres_free - Free device resource data
* @res: Pointer to devres data to free
*
* Free devres created with devres_alloc().
*/
void devres_free(void *res)
{
if (res) {
struct devres *dr = container_of(res, struct devres, data);
BUG_ON(!list_empty(&dr->node.entry));
kfree(dr);
}
}
EXPORT_SYMBOL_GPL(devres_free);
/**
* devres_add - Register device resource
* @dev: Device to add resource to
* @res: Resource to register
*
* Register devres @res to @dev. @res should have been allocated
* using devres_alloc(). On driver detach, the associated release
* function will be invoked and devres will be freed automatically.
*/
void devres_add(struct device *dev, void *res)
{
struct devres *dr = container_of(res, struct devres, data);
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
add_dr(dev, &dr->node);
spin_unlock_irqrestore(&dev->devres_lock, flags);
}
EXPORT_SYMBOL_GPL(devres_add);
static struct devres *find_dr(struct device *dev, dr_release_t release,
dr_match_t match, void *match_data)
{
struct devres_node *node;
list_for_each_entry_reverse(node, &dev->devres_head, entry) {
struct devres *dr = container_of(node, struct devres, node);
if (node->release != release)
continue;
if (match && !match(dev, dr->data, match_data))
continue;
return dr;
}
return NULL;
}
/**
* devres_find - Find device resource
* @dev: Device to lookup resource from
* @release: Look for resources associated with this release function
* @match: Match function (optional)
* @match_data: Data for the match function
*
* Find the latest devres of @dev which is associated with @release
* and for which @match returns 1. If @match is NULL, it's considered
* to match all.
*
* RETURNS:
* Pointer to found devres, NULL if not found.
*/
void * devres_find(struct device *dev, dr_release_t release,
dr_match_t match, void *match_data)
{
struct devres *dr;
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
dr = find_dr(dev, release, match, match_data);
spin_unlock_irqrestore(&dev->devres_lock, flags);
if (dr)
return dr->data;
return NULL;
}
EXPORT_SYMBOL_GPL(devres_find);
/**
* devres_get - Find devres, if non-existent, add one atomically
* @dev: Device to lookup or add devres for
* @new_res: Pointer to new initialized devres to add if not found
* @match: Match function (optional)
* @match_data: Data for the match function
*
* Find the latest devres of @dev which has the same release function
* as @new_res and for which @match return 1. If found, @new_res is
* freed; otherwise, @new_res is added atomically.
*
* RETURNS:
* Pointer to found or added devres.
*/
void * devres_get(struct device *dev, void *new_res,
dr_match_t match, void *match_data)
{
struct devres *new_dr = container_of(new_res, struct devres, data);
struct devres *dr;
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
dr = find_dr(dev, new_dr->node.release, match, match_data);
if (!dr) {
add_dr(dev, &new_dr->node);
dr = new_dr;
new_dr = NULL;
}
spin_unlock_irqrestore(&dev->devres_lock, flags);
devres_free(new_dr);
return dr->data;
}
EXPORT_SYMBOL_GPL(devres_get);
/**
* devres_remove - Find a device resource and remove it
* @dev: Device to find resource from
* @release: Look for resources associated with this release function
* @match: Match function (optional)
* @match_data: Data for the match function
*
* Find the latest devres of @dev associated with @release and for
* which @match returns 1. If @match is NULL, it's considered to
* match all. If found, the resource is removed atomically and
* returned.
*
* RETURNS:
* Pointer to removed devres on success, NULL if not found.
*/
void * devres_remove(struct device *dev, dr_release_t release,
dr_match_t match, void *match_data)
{
struct devres *dr;
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
dr = find_dr(dev, release, match, match_data);
if (dr) {
list_del_init(&dr->node.entry);
devres_log(dev, &dr->node, "REM");
}
spin_unlock_irqrestore(&dev->devres_lock, flags);
if (dr)
return dr->data;
return NULL;
}
EXPORT_SYMBOL_GPL(devres_remove);
/**
* devres_destroy - Find a device resource and destroy it
* @dev: Device to find resource from
* @release: Look for resources associated with this release function
* @match: Match function (optional)
* @match_data: Data for the match function
*
* Find the latest devres of @dev associated with @release and for
* which @match returns 1. If @match is NULL, it's considered to
* match all. If found, the resource is removed atomically and freed.
*
* RETURNS:
* 0 if devres is found and freed, -ENOENT if not found.
*/
int devres_destroy(struct device *dev, dr_release_t release,
dr_match_t match, void *match_data)
{
void *res;
res = devres_remove(dev, release, match, match_data);
if (unlikely(!res))
return -ENOENT;