| Message ID | 1438007451-8553-4-git-send-email-vladimir_zapolskiy@mentor.com |
|---|---|
| State | Accepted |
| Headers | show |
On Mon, Jul 27, 2015 at 05:30:50PM +0300, Vladimir Zapolskiy wrote: > 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@mentor.com> Applied to for-next, thanks!
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 */
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@mentor.com> --- 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(+)