(Q asked by a colleague, a wee bit vague on details so i'm hoping i'm describing it correctly, seems like it should be easy to solve.) short form of question: what is the standard way of, at boot time, passing the kernel information to specify that a built-in driver should *not* be started? longer form of question: target system has two "slots", each of which contains a distinct embedded system running linux. both of those systems run the same kernel, *except* that, in slot 0, kernel should start and run a particular driver whereas, in slot 1, the kernel should *not* start that particular driver, whereupon apps on that system will fall back and do things differently. (apparently, the apps will use the simple existence of the driver's /dev/driver special device file to identify which approach to take.) as i understand it, then, whether or not that driver should start is based simply on being able to identify the slot the board is in, and this is something that is allegedly available to u-boot, which will then pass the appropriate info on the kernel command line, telling the kernel whether or not to start that driver. so far, so good. question is, what is the "appropriate" info to pass to the kernel to identify whether or not to start a (built-in) driver? my initial reaction was, define a simple module parameter, say "run", which is tested immediately upon driver startup, and if it's "0", just exit; otherwise, run normally. and then u-boot would add to the boot line: ... drivername.run=0 ... am i overthinking this? i'm used to module parameters being used to pass info to drivers and modules to *customize* their behaviour, not to simply say whether to run or not. is this a reasonable way to do this? is there a better/standard way? and is there a simple example of that in the current kernel source? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================