status = "disabled"

[Warner Losh]

On Feb 2, 2014, at 8:20 AM, Nathan Whitehorn wrote:

> On 02/02/14 05:55, Weiß, Jürgen wrote:
>> 
>> it seems your recent changes (261351) discarded a call to fdt_is_enabled
>> for devices on simplebus. So 'status = "disabled" ' does not work
>> anymore in arm dts.
>> 
> That's actually required to make some hardware work ("disabled" may just mean the clock is turned off and needs to be turned back on, which means you absolutely do want that device probed). The device drivers themselves, not the bus, should be checking this property and interpreting it. If this has actually broken hardware, we could add a temporary #ifdef __arm__ check to the simplebus tree-walker while the relevant drivers get fixed up.

I suspect that it is going to be a cooperation between the bus and the driver.  Eg, we want them probed, and their resources allocated, but we otherwise don't want the driver to interact with the hardware. So a serial driver wouldn't create /dev/ttyUx nodes, a network driver wouldn't try to attach an if_net, etc. Also, we need an interface, eventually, that will allow us to turn them back on, but that can be problematic since one of the resources the drivers use is hardware pins, which are multiplexed with other drivers...

Warner