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Commit 48e9743d authored by Vladimir Zapolskiy's avatar Vladimir Zapolskiy Committed by Wolfram Sang
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i2c: core: add and export of_get_i2c_adapter_by_node() interface 



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: default avatarVladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 611e12ea

drivers/i2c/i2c-core.c

+18 −0
Original line number Diff line number Diff line
@@ -1371,6 +1371,24 @@ 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 */

include/linux/i2c.h

+7 −0
Original line number Diff line number Diff line
@@ -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 */