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fpga: bridge: add owner module and take its refcount

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The current implementation of the fpga bridge assumes that the low-level
module registers a driver for the parent device and uses its owner pointer
to take the module's refcount. This approach is problematic since it can
lead to a null pointer dereference while attempting to get the bridge if
the parent device does not have a driver.

To address this problem, add a module owner pointer to the fpga_bridge
struct and use it to take the module's refcount. Modify the function for
registering a bridge to take an additional owner module parameter and
rename it to avoid conflicts. Use the old function name for a helper macro
that automatically sets the module that registers the bridge as the owner.
This ensures compatibility with existing low-level control modules and
reduces the chances of registering a bridge without setting the owner.

Also, update the documentation to keep it consistent with the new interface
for registering an fpga bridge.

Other changes: opportunistically move put_device() from __fpga_bridge_get()
to fpga_bridge_get() and of_fpga_bridge_get() to improve code clarity since
the bridge device is taken in these functions.

Fixes: 21aeda950c ("fpga: add fpga bridge framework")
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Xu Yilun <yilun.xu@intel.com>
Reviewed-by: Russ Weight <russ.weight@linux.dev>
Signed-off-by: Marco Pagani <marpagan@redhat.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Link: https://lore.kernel.org/r/20240322171839.233864-1-marpagan@redhat.com
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
This commit is contained in:
Marco Pagani 2024-03-22 18:18:37 +01:00 committed by Xu Yilun
parent 4d4d2d4346
commit 1da11f8220
No known key found for this signature in database
GPG Key ID: FCB70381A4A08CDA
3 changed files with 43 additions and 31 deletions
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7
Documentation/driver-api/fpga/fpga-bridge.rst
View File

@ -6,9 +6,12 @@ API to implement a new FPGA bridge
* struct fpga_bridge - The FPGA Bridge structure
* struct fpga_bridge_ops - Low level Bridge driver ops
* fpga_bridge_register() - Create and register a bridge
* __fpga_bridge_register() - Create and register a bridge
* fpga_bridge_unregister() - Unregister a bridge
The helper macro ``fpga_bridge_register()`` automatically sets
the module that registers the FPGA bridge as the owner.
.. kernel-doc:: include/linux/fpga/fpga-bridge.h
:functions: fpga_bridge
@ -16,7 +19,7 @@ API to implement a new FPGA bridge
:functions: fpga_bridge_ops
.. kernel-doc:: drivers/fpga/fpga-bridge.c
:functions: fpga_bridge_register
:functions: __fpga_bridge_register
.. kernel-doc:: drivers/fpga/fpga-bridge.c
:functions: fpga_bridge_unregister

57
drivers/fpga/fpga-bridge.c
View File

@ -55,33 +55,26 @@ int fpga_bridge_disable(struct fpga_bridge *bridge)
}
EXPORT_SYMBOL_GPL(fpga_bridge_disable);
static struct fpga_bridge *__fpga_bridge_get(struct device *dev,
static struct fpga_bridge *__fpga_bridge_get(struct device *bridge_dev,
struct fpga_image_info *info)
{
struct fpga_bridge *bridge;
int ret = -ENODEV;
bridge = to_fpga_bridge(dev);
bridge = to_fpga_bridge(bridge_dev);
bridge->info = info;
if (!mutex_trylock(&bridge->mutex)) {
ret = -EBUSY;
goto err_dev;
}
if (!mutex_trylock(&bridge->mutex))
return ERR_PTR(-EBUSY);
if (!try_module_get(dev->parent->driver->owner))
goto err_ll_mod;
if (!try_module_get(bridge->br_ops_owner)) {
mutex_unlock(&bridge->mutex);
return ERR_PTR(-ENODEV);
}
dev_dbg(&bridge->dev, "get\n");
return bridge;
err_ll_mod:
mutex_unlock(&bridge->mutex);
err_dev:
put_device(dev);
return ERR_PTR(ret);
}
/**
@ -98,13 +91,18 @@ err_dev:
struct fpga_bridge *of_fpga_bridge_get(struct device_node *np,
struct fpga_image_info *info)
{
struct device *dev;
struct fpga_bridge *bridge;
struct device *bridge_dev;
dev = class_find_device_by_of_node(&fpga_bridge_class, np);
if (!dev)
bridge_dev = class_find_device_by_of_node(&fpga_bridge_class, np);
if (!bridge_dev)
return ERR_PTR(-ENODEV);
return __fpga_bridge_get(dev, info);
bridge = __fpga_bridge_get(bridge_dev, info);
if (IS_ERR(bridge))
put_device(bridge_dev);
return bridge;
}
EXPORT_SYMBOL_GPL(of_fpga_bridge_get);
@ -125,6 +123,7 @@ static int fpga_bridge_dev_match(struct device *dev, const void *data)
struct fpga_bridge *fpga_bridge_get(struct device *dev,
struct fpga_image_info *info)
{
struct fpga_bridge *bridge;
struct device *bridge_dev;
bridge_dev = class_find_device(&fpga_bridge_class, NULL, dev,
@ -132,7 +131,11 @@ struct fpga_bridge *fpga_bridge_get(struct device *dev,
if (!bridge_dev)
return ERR_PTR(-ENODEV);
return __fpga_bridge_get(bridge_dev, info);
bridge = __fpga_bridge_get(bridge_dev, info);
if (IS_ERR(bridge))
put_device(bridge_dev);
return bridge;
}
EXPORT_SYMBOL_GPL(fpga_bridge_get);
@ -146,7 +149,7 @@ void fpga_bridge_put(struct fpga_bridge *bridge)
dev_dbg(&bridge->dev, "put\n");
bridge->info = NULL;
module_put(bridge->dev.parent->driver->owner);
module_put(bridge->br_ops_owner);
mutex_unlock(&bridge->mutex);
put_device(&bridge->dev);
}
@ -316,18 +319,19 @@ static struct attribute *fpga_bridge_attrs[] = {
ATTRIBUTE_GROUPS(fpga_bridge);
/**
* fpga_bridge_register - create and register an FPGA Bridge device
* __fpga_bridge_register - create and register an FPGA Bridge device
* @parent: FPGA bridge device from pdev
* @name: FPGA bridge name
* @br_ops: pointer to structure of fpga bridge ops
* @priv: FPGA bridge private data
* @owner: owner module containing the br_ops
*
* Return: struct fpga_bridge pointer or ERR_PTR()
*/
struct fpga_bridge *
fpga_bridge_register(struct device *parent, const char *name,
const struct fpga_bridge_ops *br_ops,
void *priv)
__fpga_bridge_register(struct device *parent, const char *name,
const struct fpga_bridge_ops *br_ops,
void *priv, struct module *owner)
{
struct fpga_bridge *bridge;
int id, ret;
@ -357,6 +361,7 @@ fpga_bridge_register(struct device *parent, const char *name,
bridge->name = name;
bridge->br_ops = br_ops;
bridge->br_ops_owner = owner;
bridge->priv = priv;
bridge->dev.groups = br_ops->groups;
@ -386,7 +391,7 @@ error_kfree:
return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(fpga_bridge_register);
EXPORT_SYMBOL_GPL(__fpga_bridge_register);
/**
* fpga_bridge_unregister - unregister an FPGA bridge

10
include/linux/fpga/fpga-bridge.h
View File

@ -45,6 +45,7 @@ struct fpga_bridge_info {
* @dev: FPGA bridge device
* @mutex: enforces exclusive reference to bridge
* @br_ops: pointer to struct of FPGA bridge ops
* @br_ops_owner: module containing the br_ops
* @info: fpga image specific information
* @node: FPGA bridge list node
* @priv: low level driver private date
@ -54,6 +55,7 @@ struct fpga_bridge {
struct device dev;
struct mutex mutex; /* for exclusive reference to bridge */
const struct fpga_bridge_ops *br_ops;
struct module *br_ops_owner;
struct fpga_image_info *info;
struct list_head node;
void *priv;
@ -79,10 +81,12 @@ int of_fpga_bridge_get_to_list(struct device_node *np,
struct fpga_image_info *info,
struct list_head *bridge_list);
#define fpga_bridge_register(parent, name, br_ops, priv) \
__fpga_bridge_register(parent, name, br_ops, priv, THIS_MODULE)
struct fpga_bridge *
fpga_bridge_register(struct device *parent, const char *name,
const struct fpga_bridge_ops *br_ops,
void *priv);
__fpga_bridge_register(struct device *parent, const char *name,
const struct fpga_bridge_ops *br_ops, void *priv,
struct module *owner);
void fpga_bridge_unregister(struct fpga_bridge *br);
#endif /* _LINUX_FPGA_BRIDGE_H */