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Wed, 19 Aug 2026 23:36:00 -0700 (PDT) X-Received: by 2002:a17:90b:1e4a:b0:37f:c97a:939f with SMTP id 98e67ed59e1d1-39580ace5fcmr18433908a91.7.1787207759901; Wed, 19 Aug 2026 23:35:59 -0700 (PDT) Received: from [10.218.42.113] ([202.46.22.19]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3957fbba811sm6020928a91.13.2026.08.19.23.35.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Aug 2026 23:35:59 -0700 (PDT) Message-ID: Date: Thu, 20 Aug 2026 12:05:54 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] net: qrtr: Send HELLO message on endpoint register To: Manivannan Sadhasivam Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-arm-msm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Chris Lew , Deepak Kumar Singh References: <20260807-qrtr-hello-on-ep-register-v2-1-a7f265a42f7e@oss.qualcomm.com> <6smj6xbr4gumprpplrrw46lhe6wj63wbmcfe3nadcyp6om5cbb@tk6xtwtfz55r> Content-Language: en-US From: Pranav Mahesh Phansalkar In-Reply-To: <6smj6xbr4gumprpplrrw46lhe6wj63wbmcfe3nadcyp6om5cbb@tk6xtwtfz55r> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-GUID: x2cGwx9hAlxOH4zl1nfYc9XbsPIyQdgq X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODIwMDA0NiBTYWx0ZWRfX51Hmz2WOMHiB w2sEb9lkcphUpBBRhBEb5CqGNLp67NTlLTB01SIRMpwmx8D3TtPaPLPpqPFFTTEVd07Ouz+BL+O wh4RYSMxm54Xac0Rc3N7/TikWifozCVgTPOj7GKbnF2ZXU9s7t4fHNSR//4x6ZtmB3vXXrNyxy8 CJgvz6uZGkVbIB0c0kpYxmGhNwkwhN9Fn9BI/PXhuDVdYr1gdp7wCi/7mniJp90+l0YTFoeP4S6 LbzcsPLXJFZDM7hGaKIXUqOBfvr54DvWFN/EJHGre1TzpkA4haekiUxoMOSRbQks5Mdwq0kMLpT dp/sZqm4ti86UqVYo1XFgtAp6VLpSSEBNGs7NCVoqNk7RkNopzlUd0z0ql6hM+KbF0J2PhErwFQ VQay66i0XAWzTVEd4rfPyWXrM6SRHBK4bL7tFu6uZBM8J7K/nkf1nbIhuvCEsG3f81Ghww0J7Lm XfDbJfixzUWZmY0EF6g== X-Proofpoint-Spam-Info: AW1haW4tMjYwODIwMDA0NiBTYWx0ZWRfX6akDvEUCrOtO xma6JYzGTuc3QjYelXuNyBfTGjcQ1RaiPx0mhqoxYSZGrSEIUa9s8mbW9i7t3K1SqI/ypEka5RG WQoTfVWTQNz+XcLC6sVc/4EsTS6KruU= X-Authority-Analysis: v=2.4 cv=CN8amxrD c=1 sm=1 tr=0 ts=6a86a051 cx=c_pps a=vVfyC5vLCtgYJKYeQD43oA==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=EUspDBNiAAAA:8 a=qc3QEUOGKWWRYTEpMpUA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=rl5im9kqc5Lf4LNbBjHf:22 X-Proofpoint-ORIG-GUID: x2cGwx9hAlxOH4zl1nfYc9XbsPIyQdgq X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-19_06,2026-08-19_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 phishscore=0 bulkscore=0 clxscore=1015 spamscore=0 adultscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608200046 On 8/18/2026 3:24 PM, Manivannan Sadhasivam wrote: > On Fri, Aug 07, 2026 at 07:23:04PM +0530, Pranav Mahesh Phansalkar wrote: >> From: Chris Lew >> >> HELLO is currently handled entirely by the name server (NS): it is >> sent once as a broadcast when the NS initializes, and again as a >> reply whenever the NS receives an inbound HELLO from a remote. >> >> In a slave model, neither endpoint initiates a HELLO on its own; > What is a 'slave model'? Explain please. Some chipsets attached over MHI operate as slaves: they wait for the host to send HELLO first and never initiate. Since the host cannot tell which remotes behave this way, if the host also only replies, both sides wait on each other indefinitely and no HELLO is ever exchanged. > >> each side only replies to one it receives. Since both sides are waiting >> on the other to speak first, no HELLO is ever sent, stalling further >> communication. >> > What about the 'say_hello()' called during qrtr_ns_init()? That call fires once during qrtr module init, before any transport (mhi/smd/tun) can register an endpoint, so qrtr_all_nodes is empty and it reaches no remote peer. We have reviewed it and agree it can be removed as dead code in this series. > >> To fix this: >> - Transfer HELLO handshake ownership to the core layer. >> - Schedule a work item on endpoint registration to send a HELLO once >> the name server is bound, retrying on failure. >> - Enforce HELLO-first ordering by dropping non-HELLO packets until >> the HELLO is confirmed sent, using bool hello_sent guarded by >> ep_lock to make the gate check atomic with xmit(). >> - Skip nodes with nid == QRTR_EP_NID_AUTO in bcast_enqueue(). >> - Remove say_hello() from the name server's ctrl_cmd_hello() handler; >> the core layer is now the sole sender of the outbound HELLO. >> > From the internal QMUX documentation, I can see that a node acting as a slave > should only send HELLO packet only as a response to a HELLO packet, which > contradicts with that this patch is doing. > > Since the driver cannot differentiate between master/slave mode, it currently > broadcasts HELLO during initialization and sends HELLO as a response to the > HELLO packet received. Agreed — that is exactly why we are moving to sending HELLO at every endpoint registration instead of relying on the one-time NS-init broadcast or reply-on-receipt, neither of which reliably reaches a slave-mode remote like the MHI WLAN case. > > - Mani >