Re: [Patch] MPC Adapter: read class attribute from device tree

[Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>]

Hi Jon,

On Fri, 24 Apr 2009 11:38:04 -0400, Jon Smirl wrote:
> You're stuck because i2c hardware does not support hotplug. Since the
> hardware doesn't support hotplug there's no software support for it in
> the kernel. So you want to fall back to polled probing.
> 
> But probing is bad because it isn't standardized and coordinated, one
> device's probe can cause another device to destroy things (like set a
> voltage too high on a motherboard). Because of this probing can't be
> turned on in general.
> 
> It's possible to get to the i2c bus from user space. You could write a
> user space app that polls in your controlled environment. When you
> detect the new devices you can load the appropriate modules. Now you
> need to instantiate these new devices.
> 
> Jean, is it still possible to instantiate i2c devices from the module
> command line?

It is still possible if the driver implements the .detect() callback
(even without any address being probed by default) and uses one of the
I2C_CLIENT_INSMOD* macros. However, these macros are planned for
removal. Their replacement is the sysfs entries I have been discussing
with Michael in the past few weeks and for which he sent a patch for me
to review. This is still on my todo list, but I am very busy these
days :(

-- 
Jean Delvare