Re: [PATCH v2] net: qrtr: Send HELLO message on endpoint register

[Manivannan Sadhasivam]

On Thu, Aug 20, 2026 at 12:05:54PM +0530, Pranav Mahesh Phansalkar wrote:
> 
> 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 <christopher.lew@xxxxxxxxxxxxxxxx>
> > > 
> > > 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.
> 

Ok. Then I hope you'll send next version removing the say_hello() instance
mentioned above.

- Mani

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