of_find_i2c_adapter_by_node() call requires quite often missing
put_device(), and i2c_put_adapter() releases a device locked by
i2c_get_adapter() only. In general module_put(adapter->owner) and
put_device(dev) are not interchangeable.
This is a common error reproduction scenario as a result of the
misusage described above (for clearness this is run on iMX6 platform
with HDMI and I2C bus drivers compiled as kernel modules):
root@mx6q:~# lsmod | grep i2c
i2c_imx 10213 0
root@mx6q:~# lsmod | grep dw_hdmi_imx
dw_hdmi_imx 3631 0
dw_hdmi 11846 1 dw_hdmi_imx
imxdrm 8674 3 dw_hdmi_imx,imx_ipuv3_crtc,imx_ldb
drm_kms_helper 113765 5 dw_hdmi,imxdrm,imx_ipuv3_crtc,imx_ldb
root@mx6q:~# rmmod dw_hdmi_imx
root@mx6q:~# lsmod | grep i2c
i2c_imx 10213 -1
^^^^^
root@mx6q:~# rmmod i2c_imx
rmmod: ERROR: Module i2c_imx is in use
To fix existing users of these interfaces and to avoid any further
confusion and misusage in future, add one more interface
of_get_i2c_adapter_by_node(), it is similar to i2c_get_adapter() in
sense that an I2C bus device driver found and locked by user can be
correctly unlocked by i2c_put_adapter().
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
---
Changes from v1 to v2:
* rebased v1 1/10 on top of v2 1/4 and v2 2/4, removed put_device()
from of_get_i2c_adapter_by_node() as suggested by Thierry
* reuse of_find_i2c_adapter_by_node() to replace common code
* fix potential device refcount leakage on error path
Changes from RFC to v1:
* added new exported function declaration in include/linux/i2c.h
* added put_device(dev) call right inside of_get_i2c_adapter_by_node()
* corrected authorship of the change
drivers/i2c/i2c-core.c | 18 ++++++++++++++++++
include/linux/i2c.h | 7 +++++++
2 files changed, 25 insertions(+)
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index a7054ac..f3de2e1 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1369,6 +1369,24 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
return adapter;
}
EXPORT_SYMBOL(of_find_i2c_adapter_by_node);
+
+/* must call i2c_put_adapter() when done with returned i2c_adapter device */
+struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node)
+{
+ struct i2c_adapter *adapter;
+
+ adapter = of_find_i2c_adapter_by_node(node);
+ if (!adapter)
+ return NULL;
+
+ if (!try_module_get(adapter->owner)) {
+ put_device(&adapter->dev);
+ adapter = NULL;
+ }
+
+ return adapter;
+}
+EXPORT_SYMBOL(of_get_i2c_adapter_by_node);
#else
static void of_i2c_register_devices(struct i2c_adapter *adap) { }
#endif /* CONFIG_OF */
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index e83a738..e2c859b 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -638,6 +638,8 @@ extern struct i2c_client *of_find_i2c_device_by_node(struct device_node *node);
/* must call put_device() when done with returned i2c_adapter device */
extern struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node);
+/* must call i2c_put_adapter() when done with returned i2c_adapter device */
+struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node);
#else
static inline struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
@@ -649,6 +651,11 @@ static inline struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node
{
return NULL;
}
+
+static inline struct i2c_adapter *of_get_i2c_adapter_by_node(struct device_node *node)
+{
+ return NULL;
+}
#endif /* CONFIG_OF */
#endif /* _LINUX_I2C_H */
--
2.1.4
--
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