On Tue, Mar 22, 2011 at 11:28 PM, Mark Brown
[off-list ref] wrote:

On Tue, Mar 22, 2011 at 11:26:19PM +0900, Magnus Damm wrote:

quoted

The tca6416 driver makes use of the I2C bus for chatting
with the actual hardware device. Without this patch both
the I2C bus driver and the tca6416 driver are initialized
at the subsys_initcall() level. This may lead to problems
with the tca6416 driver being initialized before the I2C
bus driver.

While this change seems reasonable I'm curious what the problems caused
by out of order registration are?

The boot up time is delayed with 5 seconds or so due to a delay that
only happens if subsys_initcall() level is used for both tca6416 and
the I2C driver. By disabling the tca6416 driver in the kernel
configuration the delay goes away. I have not tracked it down further
than using module_init() instead of subsys_initcall() in the tca6416
driver. This because tca6416-keypad.c is the only keyboard driver that
uses subsys_initcall().

If I enable initcall_debug then I get this output:

calling  input_init+0x0/0x114 @ 1
initcall input_init+0x0/0x114 returned 0 after 0 usecs
calling  tca6416_keypad_init+0x0/0x10 @ 1
initcall tca6416_keypad_init+0x0/0x10 returned 0 after 0 usecs
calling  sh_mobile_i2c_adap_init+0x0/0xc @ 1
i2c-sh_mobile i2c-sh_mobile.0: clocks managed by runtime pm
input: tca6408-keys as
/devices/platform/i2c-sh_mobile.0/i2c-0/0-0020/input/input0
[delay]

If my interpretation of the log above is correct then
tca6416_keypad_init() is executed before sh_mobile_i2c_adap_init().

As for link order, i2c is located after input in driver/Makefile. I
believe that matches well with the log above.

Thanks,

/ magnus