Return-Path: Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: [PATCH v2] Bluetooth: Add LED triggers for HCI frames tx and rx From: Marcel Holtmann In-Reply-To: Date: Tue, 16 Aug 2016 14:33:13 +0200 Cc: "Gustavo F. Padovan" , Johan Hedberg , "David S. Miller" , "open list:BLUETOOTH DRIVERS" , Network Development , "linux-kernel@vger.kernel.org" , linux-arm-kernel Message-Id: <30869CE7-FE5E-4CAF-86FC-D140E2C0963D@holtmann.org> References: <1469939084-15603-1-git-send-email-guodong.xu@linaro.org> <1394C970-3726-4C42-A06D-0B3B3015D980@holtmann.org> To: Guodong Xu Sender: linux-kernel-owner@vger.kernel.org List-ID: Hi Guodong, >>> Two LED triggers are added into hci_dev: tx_led and rx_led. Upon ACL/SCO >>> packets available in tx or rx, the LEDs will blink. >>> >>> For each hci registration, two triggers are added into LED subsystem: >>> [hdev->name]-tx and [hdev-name]-rx. >>> Refer to Documentation/leds/leds-class.txt for usage. >>> >>> Verified on HiKey 96boards, which uses HiSilicon hi6220 SoC and TI >>> WL1835 WiFi/BT combo chip. >> >> so I have no idea what to do with adding adding hci0-rx and hci0-tx triggers. Combined with hci0-power trigger these are already 3 triggers. And if you have 2 Bluetooth controllers in your system, then you have 6 triggers. >> > > True, 6 triggers. But, taking example for other subsytems, eg. cpu > cores. On my board, I have "heartbeat cpu0 cpu1 cpu2 cpu3 cpu4 cpu5 > cpu6 cpu7". It doesn't have to mean you need all of them connected to > some LED(s). Actually, in most of the case, I only need heartbeat. > > > >> If we then maybe add another trigger, then this number just goes up and up. >> >> As far as I can tell you can only assign a single trigger to a LED. >> > > That's true. And people got a choice of which feature he wants to visualize. and as a result we keep adding senseless triggers to the kernel and bloating it up for no reason. Especially since it feels like 99% of the LED triggers are not used at all. This makes no sense to me. >> So this means to even use these triggers, you need now 3 LEDs per Bluetooth controller. How is that useful for anybody in a real system? Maybe I am missing something here and somehow there is magic to combine triggers, but I have not found it yet. So please someone enlighten me on how this is suppose to be used with real devices. >> >> Recently I have added a simple bluetooth-power trigger that combines all Bluetooth controllers into a single trigger. If any of them is enabled, then you can control your LED. Which makes a lot more sense to me since you most likely have a single Bluetooth LED on your system. And you want it to show the correct state no matter what Bluetooth controller is in use. However I can see the case that someone might want to assign one specific Bluetooth controller to a LED status. >> >> So instead of adding many independent triggers to each controller, why not create one global bluetooth trigger and one individual bluetooth-hci0 trigger for each controller. And the combine power, tx, rx and whatever else we need to trigger the LED for? >> > > When I starting this work, I referred to WiFi system. See > CONFIG_MAC80211_LEDS. WiFi system implements these types of triggers " > phy0rx phy0tx phy0assoc phy0radio" for each 'controller'. And I actually wonder who ever used these triggers. You need 4 LEDs to visualize the WiFi status. Which systems has 4 LEDs to spare to visualize this. > Besides, there are also RFKILL which stands for WiFi/BT power status. > RFKILL adds triggers for each module too. Eg. in the below example, I > have one WiFi (phy0), one BT (hci0). Trigger rfkill1 equals to > hci0-power. > > Ref: here are all LED triggers I found in my 96boards/HiKey: > > # cat trigger > none kbd-scrollock kbd-numlock kbd-capslock kbd-kanalock kbd-shiftlock > kbd-altgrlock kbd-ctrllock kbd-altlock kbd-shiftllock kbd-shiftrlock > kbd-ctrlllock kbd-ctrlrlock mmc0 mmc1 heartbeat cpu0 cpu1 cpu2 cpu3 > cpu4 cpu5 cpu6 cpu7 mmc2 rfkill0 phy0rx phy0tx phy0assoc phy0radio > hci0-power hci0-tx [hci0-rx] rfkill1 And how many LEDs do you have in the your system? I think you are making my point here. So I think what we need to do is to not add to this madness and instead create one "bluetooth" LED trigger that combines power and TX/RX for all controllers. And then allow for individual "bluetooth-hci0" LED triggers so that you can bind a single Bluetooth controller to a single LED. For me, if I can not combine hci0-power, hci0-tx and hci0-rx into a single LED, it becomes utterly useless on pretty much every system that is out there. Regards Marcel