The series fixes i2c bus device refcounting for clients of i2c_get_adapter(),
of_find_i2c_adapter_by_node() and of_find_i2c_device_by_node() interfaces.
The v2 3/4 change adds and exports new of_get_i2c_adapter_by_node()
interface of i2c core, v2 4/4 is an unchanged version of v1 10/10, which
utilizes this new interface in order to fix the refcounting bug described
below in detail.
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 (this is run on iMX6 platform with
HDMI and I2C bus drivers compiled as kernel modules for clearness):
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().
Mainly the change is addressed to multiple DRM users of I2C bus device
interfaces, but at the moment just one client inside drivers/i2c/* is fixed.
The change is based on Wolfram's i2c/for-next branch, 19e0ff42338
Changes from v1 to v2:
* added two more patches 1/4 and 2/4 fixing i2c bus device refcounting,
thanks to Thierry for the idea of 2/4 change,
* 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,
* defer changes in 8 broken DRM and fbdev clients until i2c-core changes
are added to linux-next (or preferably 4.2.0-rc Linus' branch, if possible)
to improve signal/noise ratio on mailing lists.
v1 of the series with fixes on client side can be found at
http://permalink.gmane.org/gmane.linux.drivers.i2c/23652
RFC of the v1 01/10 change is http://www.spinics.net/lists/linux-i2c/msg20257.html
Vladimir Zapolskiy (4):
i2c: core: fix leaked device refcount on of_find_i2c_* error path
i2c: core: manage i2c bus device refcount in i2c_[get|put]_adapter
i2c: core: add and export of_get_i2c_adapter_by_node() interface
i2c: arb-gpio-challenge: use of_get_i2c_adapter_by_node interface
drivers/i2c/i2c-core.c | 53 +++++++++++++++++++++++++-----
drivers/i2c/muxes/i2c-arb-gpio-challenge.c | 3 +-
include/linux/i2c.h | 7 ++++
3 files changed, 53 insertions(+), 10 deletions(-)
--
2.1.4
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