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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
3 changed files with 43 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/linux/fpga/fpga-bridge.h
+7 -3
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@@ -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 */