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Native PCIe Enclosure Management (NPEM, PCIe r6.1 sec 6.28) allows managing LEDs in storage enclosures. NPEM is indication oriented and it does not give direct access to LEDs. Although each indication *could* represent an individual LED, multiple indications could also be represented as a single, multi-color LED or a single LED blinking in a specific interval. The specification leaves that open. Each enabled indication (capability register bit on) is represented as a ledclass_dev which can be controlled through sysfs. For every ledclass device only 2 brightness states are allowed: LED_ON (1) or LED_OFF (0). This corresponds to the NPEM control register (Indication bit on/off). Ledclass devices appear in sysfs as child devices (subdirectory) of PCI device which has an NPEM Extended Capability and indication is enabled in NPEM capability register. For example, these are LEDs created for pcieport "10000:02:05.0" on my setup: leds/ ├── 10000:02:05.0:enclosure:fail ├── 10000:02:05.0:enclosure:locate ├── 10000:02:05.0:enclosure:ok └── 10000:02:05.0:enclosure:rebuild They can be also found in "/sys/class/leds" directory. The parent PCIe device domain/bus/device/function address is used to guarantee uniqueness across leds subsystem. To enable/disable a "fail" indication, the "brightness" file can be edited: echo 1 > ./leds/10000:02:05.0:enclosure:fail/brightness echo 0 > ./leds/10000:02:05.0:enclosure:fail/brightness PCIe r6.1, sec 7.9.19.2 defines the possible indications. Multiple indications for same parent PCIe device can conflict and hardware may update them when processing new request. To avoid issues, driver refresh all indications by reading back control register. This driver expects to be the exclusive NPEM extended capability manager. It waits up to 1 second after imposing new request, it doesn't verify if controller is busy before write, and it assumes the mutex lock gives protection from concurrent updates. If _DSM LED management is available, we assume the platform may be using NPEM for its own purposes (see PCI Firmware Spec r3.3 sec 4.7), so the driver does not use NPEM. A future patch will add _DSM support; an info message notes whether NPEM or _DSM is being used. NPEM is a PCIe extended capability so it should be registered in pcie_init_capabilities() but it is not possible due to LED dependency. The parent pci_device must be added earlier for led_classdev_register() to be successful. NPEM does not require configuration on kernel side, so it is safe to register LED devices later. Link: https://lore.kernel.org/r/20240904104848.23480-3-mariusz.tkaczyk@linux.intel.com Suggested-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Tested-by: Stuart Hayes <stuart.w.hayes@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> |
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| .. | ||
| controller | ||
| endpoint | ||
| hotplug | ||
| msi | ||
| pcie | ||
| pwrctl | ||
| switch | ||
| access.c | ||
| ats.c | ||
| bus.c | ||
| devres.c | ||
| doe.c | ||
| ecam.c | ||
| host-bridge.c | ||
| iomap.c | ||
| iov.c | ||
| irq.c | ||
| Kconfig | ||
| Makefile | ||
| mmap.c | ||
| npem.c | ||
| of_property.c | ||
| of.c | ||
| p2pdma.c | ||
| pci-acpi.c | ||
| pci-bridge-emul.c | ||
| pci-bridge-emul.h | ||
| pci-driver.c | ||
| pci-label.c | ||
| pci-mid.c | ||
| pci-pf-stub.c | ||
| pci-stub.c | ||
| pci-sysfs.c | ||
| pci.c | ||
| pci.h | ||
| probe.c | ||
| proc.c | ||
| quirks.c | ||
| remove.c | ||
| rom.c | ||
| search.c | ||
| setup-bus.c | ||
| setup-res.c | ||
| slot.c | ||
| syscall.c | ||
| vc.c | ||
| vgaarb.c | ||
| vpd.c | ||
| xen-pcifront.c | ||