On 8/27/19 4:03 PM, Akinobu Mita wrote: > 2019年8月25日(日) 0:53 Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>: >> >> On 8/23/19 6:00 PM, Akinobu Mita wrote: >>> 2019年8月20日(火) 3:38 Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>: >>>> >>>> On 8/19/19 8:22 PM, Jacek Anaszewski wrote: >>>>> On 8/19/19 4:38 PM, Pavel Machek wrote: >>>>>> On Sat 2019-08-17 22:07:43, Jacek Anaszewski wrote: >>>>>>> On 8/17/19 4:55 PM, Pavel Machek wrote: >>>>>>>> On Fri 2019-08-16 01:59:58, Akinobu Mita wrote: >>>>>>>>> This allows LEDs to be controlled by block device activity. >>>>>>>>> >>>>>>>>> We already have ledtrig-disk (LED disk activity trigger), but the lower >>>>>>>>> level disk drivers need to utilize ledtrig_disk_activity() to make the >>>>>>>>> LED blink. >>>>>>>>> >>>>>>>>> The LED block device trigger doesn't require the lower level drivers to >>>>>>>>> have any instrumentation. The activity is collected by polling the disk >>>>>>>>> stats. >>>>>>>>> >>>>>>>>> Example: >>>>>>>>> >>>>>>>>> echo block-nvme0n1 > /sys/class/leds/diy/trigger >>>>>>>> >>>>>>>> Lets use one trigger "block" and have the device as a parameter, >>>>>>>> please. >>>>>>>> >>>>>>>> We already have 1000 cpu triggers on 1000 cpu machines, and yes, its a >>>>>>>> disaster we'll need to fix. Lets not repeat the same mistake here. >>>>>>>> >>>>>>>> I guess it may be slightly more work. Sorry about that. >>>>>>> >>>>>>> We should be able to list available block devices to set, >>>>>>> so the problem would be not avoided anyway. >>>>>> >>>>>> Should we? We need to list triggers, but we may not list all the devices... >>>>> >>>>> This is similar to usbport trigger that lists available >>>>> ports as files in a sub-directory. We might eventually go >>>>> in this direction. >>>> >>>> I must withdraw this statement. This is not similar to usbport >>>> trigger. The difference is that with ledtrig-block we have separate >>>> triggers per each device and I am not aware if there is some centralized >>>> mechanism similar to blocking_notifier_chain (usb_notifier_list >>>> in drivers/usb/core/notify.c) available for block devices, that >>>> would allow to gather all available block devs under common trigger. >>>> >>>> Moreover I remember Greg once discouraged using notifier chains >>>> as they are unsafe, so we would need some other solution anyway. >>> >>> I start thinking that we should implement the LED block device activity >>> trigger in userspace. The userspace application firstly activates >>> one-shot LED trigger and periodically reads /sys/block/<disk>/stat and >>> writes /sys/class/leds/<led>/shot if there is any disk activity. >> >> This would suboptimal solution. I have another idea - let's get back >> to the implementation of ledtrig-blk in genhd.c. We would be registering >> one trigger on module initialization in a function with __init modifier. >> Then we would need to add/remove triggers to the ledtrig-blk in >> register_blkdev()/unregister_blkdev(). And registered triggers would >> be listed in block_devs directory created by the trigger. >> >> You can compare how drivers/usb/core/ledtrig-usbport.c maintains >> similar directory of usb ports. > > It could be possible, but I have yet another idea. What about introducing > /proc/led-triggers and /sys/class/leds/<led>/current-trigger? > The /sys/class/leds/<led>/trigger will be obsoleted by these two files. > > The /proc/led-triggers is read only and no PAGE_SIZE limitation by the > seq_file interface. So we can list all triggers in this file. > > The /sys/class/leds/<led>/current-trigger is almost identical to > /sys/class/leds/<led>/trigger. The only difference is that > 'current-trigger' only shows the current trigger name. There's not need to come up with yet another trigger interface. We just need to convert sysfs trigger attribute type to binary. -- Best regards, Jacek Anaszewski
