An issue with the path of SPMI nodes under /sys/bus/... was reported in https://lkml.org/lkml/2014/4/23/312. The symptom is that two different grandchild nodes of the spmi with the same node-name@unit-address will result in attempting to create duplicate links at /sys/bus/platform/devices/unit-address.node-name. It turns out that the specific example provided might not be an expected configuration for current hardware, but the reported trap remains an issue. I have been poking at the problem, trying to figure out how to cleanly fix the issue without breaking devicetree device creation. The first patch in the series is the one that may be a very bad idea. Or it may help show the way forward to deal with what I think is the major underlying problem. I have not finished investigating the possible negative side effects. And I am still thinking whether this is a conceptually good approach, or whether it is simply an expediant hack that hides the underlying problem. But I am throwing this out prematurely because I have mentioned it to several people, and I want to make it visible to everyone involved. The underlying architectural problem (in my opinion) is that a lot of devices are created by the device tree infrastructure as platform devices, when they truly should not be platform devices. They should not be platform devices because they are not physically on a platform bus, they are instead somewhere below some other bus. The first patch in this series is a hack which results in the devices still being represented by "struct platform_device" objects, but with a link to their parent's "struct bus_type" instead of to &platform_bus_type. The second patch does not require the first patch. The second patch provides a mechanism to allow subsystems to provide a method of naming devices to avoid name collisions. The third patch provides an example of a subsystem using the new feature provided by the second patch. The resulting device naming and soft links from applying all three patches, or just the second and third patches are: ===== no patches applied: $ ls /sys/devices/ ARMv7 Krait cpu-pmu.1 platform software tracepoint breakpoint cpus.0 soc.2 system virtual $ ls /sys/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 100.qcom,revid driver subsystem 3100.qcom,pm8x41-adc-usr gpios.18 uevent 6000.qcom,rtc power $ ls /sys/bus/platform/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 100.qcom,revid driver subsystem 3100.qcom,pm8x41-adc-usr gpios.18 uevent 6000.qcom,rtc power $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-01/ b040.pm8xxx-pwm driver uevent d000.pm8xxx-pwm-led power d800.pm8xxx-wled subsystem $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-04/ driver power subsystem uevent $ ls /sys/bus/spmi/devices/ 0-00 0-01 0-04 spmi-0 $ ls /sys/bus/platform/devices/ 100.qcom,revid fc4cf000.qcom,spmi 3100.qcom,pm8x41-adc-usr fd484000.hwlock 6000.qcom,rtc fd510000.pinctrl alarmtimer fd8c0000.clock-controller b040.pm8xxx-pwm gpio_keys.5 cpu-pmu.1 gpios.18 cpus.0 iio-thermal.4 d000.pm8xxx-pwm-led pm8841-s1.6 d800.pm8xxx-wled pm8841-s2.7 f9000000.interrupt-controller pm8941-l3.11 f9011000.smem pm8941-l6.12 f9012000.regulator reg-dummy f9020000.timer regulator-l11.14 f9088000.clock-controller regulator-l19.15 f9098000.clock-controller regulator-l20.16 f90a8000.clock-controller regulator-l22.17 f90b8000.clock-controller regulator-l9.13 f9824900.sdhc regulator-s1.8 f991e000.serial regulator-s2.9 f9924000.i2c2 regulator-s3.10 f9928000.i2c6 regulatory.0 f9bff000.rng snd-soc-dummy fc400000.clock-controller soc.2 fc4281d0.qcom,mpm timer.3 fc4ab000.restart ===== all three patches applied: $ ls /sys/devices/ ARMv7 Krait cpu-pmu.1 platform software tracepoint breakpoint cpus.0 soc.2 system virtual $ ls /sys/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 0-00:100.qcom,revid driver 0-00:3100.qcom,pm8x41-adc-usr power 0-00:6000.qcom,rtc subsystem 0-00:gpios uevent $ ls /sys/bus/platform/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 0-00:100.qcom,revid driver 0-00:3100.qcom,pm8x41-adc-usr power 0-00:6000.qcom,rtc subsystem 0-00:gpios uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-01/ 0-01:b040.pm8xxx-pwm driver uevent 0-01:d000.pm8xxx-pwm-led power 0-01:d800.pm8xxx-wled subsystem $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-04/ 0-04:100.qcom,revid power uevent driver subsystem $ ls /sys/bus/spmi/devices/ 0-00 0-01:b040.pm8xxx-pwm 0-00:100.qcom,revid 0-01:d000.pm8xxx-pwm-led 0-00:3100.qcom,pm8x41-adc-usr 0-01:d800.pm8xxx-wled 0-00:6000.qcom,rtc 0-04 0-00:gpios 0-04:100.qcom,revid 0-01 spmi-0 $ ls /sys/bus/platform/devices/ alarmtimer f9bff000.rng cpu-pmu.1 fc400000.clock-controller cpus.0 fc4281d0.qcom,mpm f9000000.interrupt-controller fc4ab000.restart f9011000.smem fc4cf000.qcom,spmi f9012000.regulator fd484000.hwlock f9020000.timer fd510000.pinctrl f9088000.clock-controller fd8c0000.clock-controller f9098000.clock-controller gpio_keys.5 f90a8000.clock-controller iio-thermal.4 f90b8000.clock-controller reg-dummy f9824900.sdhc regulatory.0 f991e000.serial snd-soc-dummy f9924000.i2c2 soc.2 f9928000.i2c6 timer.3 ===== patches 2 and 3 applied: $ ls /sys/devices/ ARMv7 Krait cpu-pmu.1 platform software tracepoint breakpoint cpus.0 soc.2 system virtual $ ls /sys/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 0-00:100.qcom,revid driver 0-00:3100.qcom,pm8x41-adc-usr power 0-00:6000.qcom,rtc subsystem 0-00:gpios uevent $ ls /sys/bus/platform/devices/soc.2/ f9000000.interrupt-controller fc4281d0.qcom,mpm f9011000.smem fc4ab000.restart f9012000.regulator fc4cf000.qcom,spmi f9020000.timer fd484000.hwlock f9088000.clock-controller fd510000.pinctrl f9098000.clock-controller fd8c0000.clock-controller f90a8000.clock-controller gpio_keys.5 f90b8000.clock-controller iio-thermal.4 f9824900.sdhc modalias f991e000.serial power f9924000.i2c2 subsystem f9928000.i2c6 timer.3 f9bff000.rng uevent fc400000.clock-controller $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/ driver modalias power spmi-0 subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/ 0-00 0-01 0-04 power subsystem uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-00/ 0-00:100.qcom,revid driver 0-00:3100.qcom,pm8x41-adc-usr power 0-00:6000.qcom,rtc subsystem 0-00:gpios uevent $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-01/ 0-01:b040.pm8xxx-pwm driver uevent 0-01:d000.pm8xxx-pwm-led power 0-01:d800.pm8xxx-wled subsystem $ ls /sys/bus/platform/devices/soc.2/fc4cf000.qcom,spmi/spmi-0/0-04/ 0-04:100.qcom,revid power uevent driver subsystem $ ls /sys/bus/spmi/devices/ 0-00 0-01 0-04 spmi-0 $ ls /sys/bus/platform/devices/ 0-00:100.qcom,revid fc4281d0.qcom,mpm 0-00:3100.qcom,pm8x41-adc-usr fc4ab000.restart 0-00:6000.qcom,rtc fc4cf000.qcom,spmi 0-00:gpios fd484000.hwlock 0-01:b040.pm8xxx-pwm fd510000.pinctrl 0-01:d000.pm8xxx-pwm-led fd8c0000.clock-controller 0-01:d800.pm8xxx-wled gpio_keys.5 0-04:100.qcom,revid iio-thermal.4 alarmtimer pm8841-s1.6 cpu-pmu.1 pm8841-s2.7 cpus.0 pm8941-l3.11 f9000000.interrupt-controller pm8941-l6.12 f9011000.smem reg-dummy f9012000.regulator regulator-l11.14 f9020000.timer regulator-l19.15 f9088000.clock-controller regulator-l20.16 f9098000.clock-controller regulator-l22.17 f90a8000.clock-controller regulator-l9.13 f90b8000.clock-controller regulator-s1.8 f9824900.sdhc regulator-s2.9 f991e000.serial regulator-s3.10 f9924000.i2c2 regulatory.0 f9928000.i2c6 snd-soc-dummy f9bff000.rng soc.2 fc400000.clock-controller timer.3 -- 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
