linux-kernel - Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160719053917.GB90550@worksta>
Date:	Mon, 18 Jul 2016 22:39:17 -0700
From:	Bin Gao <bin.gao@...ux.intel.com>
To:	Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Bin Gao <bin.gao@...el.com>,
	Chandra Sekhar Anagani <chandra.sekhar.anagani@...el.com>
Subject: Re: [PATCH 1/2] usb: typec: Add USB Power Delivery sink port support

On Mon, Jul 18, 2016 at 10:07:24AM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> Bin Gao <bin.gao@...ux.intel.com> writes:
> >> > +int pd_sink_queue_msg(struct pd_sink_msg *msg)
> >> > +{
> >> > +	unsigned long flags;
> >> > +	struct pd_sink_port *port;
> >> > +
> >> > +	if (msg->port < 0 || msg->port >= MAX_NR_SINK_PORTS) {
> >> > +		pr_err("Invalid port number\n");
> >> > +		return -EINVAL;
> >> > +	}
> >> > +
> >> > +	port = sink_ports[msg->port];
> >> > +
> >> > +	spin_lock_irqsave(&port->rx_lock, flags);
> >> > +	list_add_tail(&msg->list, &port->rx_list);
> >> > +	spin_unlock_irqrestore(&port->rx_lock, flags);
> >> > +
> >> > +	queue_work(port->rx_wq, &port->rx_work);
> >> 
> >> can we really queue several messages at a time? It seems unfeasible to
> >> me. It's not like we can queue several power request in a role. Why do
> >> you need this workqueue? Why don't you process message here, in place?
> > Some Type-C chargers send two messages in a short duration(less than 1 ms),
> > e.g. a SOURCE_CAPABILITY follows the previous SOURCE_CAPABILITY, or a
> > GET_SINK_CAPABILITY follows a previous SOURCE_CAPABILITY, etc. Queuing
> > message to PD stack by Type-C phy driver typically happens in a interrupt
> > context. So in this case a nested interrupt may happen. Our whole PD
> > stack while processing one message is not re-entrant so the nested
> > interrupt would cause a problem.
> 
> keep interrupts masked for as long as necessary until your message is
> processed.

Yes, that's a right way to go. 
We'll have to document this because there might be other Type-C
PHY drivers(other than Intel Whiskey Cove PMIC) to use the PD stack.

> 
> -- 
> balbi