On Wed, 18 Oct 2017, Rob Herring wrote: > On Wed, Oct 18, 2017 at 11:40 AM, Robert P. J. Day > <rpjday@xxxxxxxxxxxxxx> wrote: > > > > (WARNING: sort of newbie alert, but you know that, right? :-) > > > > was perusing online tutorial on customizing device trees here: > > > > http://developer.toradex.com/device-tree-customization > > Never seen that one. apparently, i picked a bad example to ask about, then. :-) > > and got a bit confused about the part describing how to (as i read > > it) "overwrite" entire nodes. > > > > first, part on "overwriting properties" makes perfect sense -- > > here's an example in that piece about overwriting default USB > > mode: > > > > &usb0 { > > dr_mode = "host"; > > }; > > > > so, as i've always understood it, the above will do one of two > > things: > > > > 1) if that property is not set in the node referenced by that label, > > it will be *added* to what is already there, or > > > > 2) if that property is already set (to whatever), it will be > > overwritten > > > > so far, so good? > > Yes. right, that was the easy part. > > as a special example of that right below that, there's a short > > paragraph called "Activating/Deactivating Devices" that uses this > > example: > > > > &uart4 { > > status = "okay"; > > }; > > > > but, really, that's just a special case of the first example so > > there's nothing new here. but it's the next section called > > "Overwriting nodes" that seems confusing: > > > > "Whole nodes can be overwritten by simply redefining them. Like > > overwriting properties, latter definitions overwrite earlier > > definitions." > > I don't think that's right. I think you have to use /delete-node/ > first. right, that was also my limited understanding, so you can understand my confusion based on what could be interpreted as a claim that entire nodes could be overwritten. > > wait, what? entire nodes can be overwritten by redefining them? > > the example given looks like this: > > > > "E.g. to overwrite the pin configuration of Vybrids UART2 (UART_B) > > overwrite the uart2grp node by simply redefining it in your device > > tree ..." > > > > with the device tree content > > > > &iomuxc { > > vf610-colibri { > > pinctrl_uart2: uart2grp { > > fsl,pins = < > > VF610_PAD_PTD0__UART2_TX 0x21a2 > > VF610_PAD_PTD1__UART2_RX 0x21a1 > > >; > > }; > > ... > > }; > > }; > > > > hang on ... isn't "vf610-colibri" also a "node" in this device > > tree? does the above mean that the *entire* vf610-colibri node is > > being overwritten? and that i would have to supply the entire new > > content of that node, including simply duplicating the rest of the > > content that is already there that i want to keep? (is that what > > the "..." represents?) > > No, you should get a merged vf610-colibri node with the original > contents and any new or overwritten properties from this chunk. > > IOW, only properties are overwritten. good, that makes *way* more sense, thanks for clarifying that. followup question coming shortly ... rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ======================================================================== -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
