(sorry for replying on old thread) On 11/08/17 16:54, Arnd Bergmann wrote: > On Fri, Aug 11, 2017 at 5:05 PM, Rob Herring <robh@xxxxxxxxxx> wrote: >> On Fri, Aug 11, 2017 at 9:37 AM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >>> On Fri, Aug 11, 2017 at 3:30 PM, Sudeep Holla <sudeep.holla@xxxxxxx> wrote: >>>> Since "/firmware" does not have its own "compatible" property as it's >>>> just collection of nodes representing firmware interface, it's sub-nodes >>>> are not populated during system initialization. >>>> >>>> Currently different firmware drivers search the /firmware/ node and >>>> populate the sub-node devices selectively. Instead we can populate >>>> the /firmware/ node during init to avoid more drivers continuing to >>>> populate the devices selectively. >>>> >>>> This patch adds initcall to achieve the same. >>> >>> Hmm, I'm a bit skeptical whether representing anything under /firmware >>> as a platform device is a good idea. Having a more structured way to >>> probe those seems like a good idea, but maybe a different subsystem >>> would be more appropriate. >>> >>> I do realize that a 'platform_device' has become a rather generic abstraction >>> for almost anything, but at some point we might want to draw the line >>> of what is a platform_device. >> >> I guess the question how are they different? Most of what's under >> drivers/firmware/ are platform drivers. I think they are mostly either >> smc calls or mailbox interfaces. Would there be any advantage to >> creating an smc bus or mailbox bus? > > I guess one difference I see is between things that are purely software > based (smc, efi runtime, rtas, ...) and those that talk to some > hardware other than the CPU running some firmware. > > The first category seems like a good fit for /firmware in DT and > for /sys/firmware in sysfs, while the second category would be > represented elsewhere in both DT and sysfs. > After some thoughts and looking around I see examples of lots of drivers using platform device for firmware interface including rtc-efi. So IIUC, anything exposed to userspace about sch firmware interface must be in "/sys/firmware", but I don't see any issue with kernel handling them as platform device/driver internally. -- Regards, Sudeep -- 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
