Return-Path: Subject: Re: keep alive To: Sriram V References: From: Loic Poulain Cc: linux-bluetooth@vger.kernel.org Message-ID: <578B7275.50703@intel.com> Date: Sun, 17 Jul 2016 13:56:37 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-bluetooth-owner@vger.kernel.org List-ID: Hi Sriram, > I am using a broadcom's bcm bt chip. I wanted to find if there is some > sort of "Keep Alive" Feature so that connections are not lost? You should have a look at the spec, but to make it short, Physical link is monitored/supervised at controller level (Master-Slave(s) polling). No need to explicitly send NULL data packet like WiFi/802.11. > I am keeping the bt chip turned on during sleep/suspend. However, I am > not sure if BT sends keep alive probe periodically. Can someone > clarify on this. Connection is maintained, but If there is some incoming logical link data (ACL, SCO...), Host needs to be active in order to retrieve and process this data. Actually, any data causing HCI transfer from controller to host. In case of system suspend, that means BT controller needs wakeup capability (via USB resume, out of band gpio...) to move host from suspend to active. If host does not wake up, this can cause issues at higher level (timeout, data lost...) and potentially trigger physical disconnection. Regards, Loic