On Thu, May 26, 2016 at 09:03:11AM +0800, Lu Baolu wrote:
> Hi Heikki,
>
> On 05/25/2016 07:06 PM, Heikki Krogerus wrote:
> > Hi Baolu,
> >
> > Sorry to comment this so late, but we got hardware that needs to
> > configure the mux in OS, and I noticed some problem.
>
> Comments are always welcome. :-)
>
> > We are missing
> > means to bind a port to the correct mux on multiport systems. That we
> > need to solve later in any case, but there is an other issue related
> > to the fact that the notifiers now have to be extcon devices. It's
> > related, as extcon offers no means to solve the multiport issue, but
> > in any case..
> >
> >> +struct portmux_dev *portmux_register(struct portmux_desc *desc)
> >> +{
> >> + static atomic_t portmux_no = ATOMIC_INIT(-1);
> >> + struct portmux_dev *pdev;
> >> + struct extcon_dev *edev = NULL;
> >> + struct device *dev;
> >> + int ret;
> >> +
> >> + /* parameter sanity check */
> >> + if (!desc || !desc->name || !desc->ops || !desc->dev ||
> >> + !desc->ops->cable_set_cb || !desc->ops->cable_unset_cb)
> >> + return ERR_PTR(-EINVAL);
> >> +
> >> + dev = desc->dev;
> >> +
> >> + if (desc->extcon_name) {
> >> + edev = extcon_get_extcon_dev(desc->extcon_name);
> >> + if (IS_ERR_OR_NULL(edev))
> >> + return ERR_PTR(-EPROBE_DEFER);
> >> + }
> >> +
> >> + pdev = kzalloc(sizeof(*pdev), GFP_KERNEL);
> >> + if (!pdev)
> >> + return ERR_PTR(-ENOMEM);
> >> +
> >> + pdev->desc = desc;
> >> + pdev->edev = edev;
> >> + pdev->nb.notifier_call = usb_mux_notifier;
> >> + mutex_init(&pdev->mux_mutex);
> >> +
> >> + pdev->dev.parent = dev;
> >> + dev_set_name(&pdev->dev, "portmux.%lu",
> >> + (unsigned long)atomic_inc_return(&portmux_no));
> >> + pdev->dev.groups = portmux_group;
> >> + ret = device_register(&pdev->dev);
> >> + if (ret)
> >> + goto cleanup_mem;
> >> +
> >> + dev_set_drvdata(&pdev->dev, pdev);
> >> +
> >> + if (edev) {
> >> + ret = extcon_register_notifier(edev, EXTCON_USB_HOST,
> >> + &pdev->nb);
> >> + if (ret < 0) {
> >> + dev_err(dev, "failed to register extcon notifier\n");
> >> + goto cleanup_dev;
> >> + }
> >> + }
> > So I don't actually think this is correct approach. We are forcing the
> > notifying drivers, on top of depending on this framework, depend on
> > extcon too, and that simply is too much. I don't think a USB PHY or
> > charger detection driver should be forced to generate an extcon device
> > just to satisfy the mux in general.
>
> Fair enough.
>
> >
> > Instead IMO, this framework should provide an API also for the
> > notifiers. The drivers that do the notification should not need to
> > depend on extcon at all. Instead they should be able to just request
> > an optional handle to a portmux, and use it with the function that you
> > already provide (usb_mux_change_state(), which of course needs to be
> > exported). That would make it much easier for us to make problems like
> > figuring out the correct mux for the correct port a problem for the
> > framework and not the drivers.
> >
> > extcon does not really add any value here, but it does complicate
> > things a lot. We are even exposing new sysfs attributes to control the
> > mux, complete separate from extcon.
>
> I agree with you that we should move extcon out of the framework.
>
> In order to support multiport systems, I have below proposal.
>
> Currently, we have below interfaces.
>
> struct portmux_dev *portmux_register(struct portmux_desc *desc);
> void portmux_unregister(struct portmux_dev *pdev);
>
> I will add below ones.
>
> struct portmux_dev *portmux_lookup_by_name(char *name);
> int portmux_switch(struct portmux_dev *pdev, enum port_role);
>
> The normal usage mode is
> 1) the mux device is registered as soon as a mux is detected with
> portmux_register();
> 2) In components like USB PHY or changer drivers, the mux could
> be retrieved with portmux_lookup_by_name() and controlled via
> portmux_switch().
>
> Is this helpful?
It works for me, and we can improve it later if needed.
Thanks,
--
heikki
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