linux-kernel - Re: [PATCH v2 0/2] extcon: Inform the state of both ID and VBUS pin for USB

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Date:	Thu, 28 May 2015 11:45:31 +0300
From:	"Ivan T. Ivanov" <iivanov@...sol.com>
To:	Chanwoo Choi <cwchoi00@...il.com>
Cc:	linux-kernel@...r.kernel.org, rogerq@...com, r.baldyga@...sung.com,
	peter.chen@...escale.com, kishon@...com, balbi@...com,
	cw00.choi@...sung.com, myungjoo.ham@...sung.com
Subject: Re: [PATCH v2 0/2] extcon: Inform the state of both ID and VBUS pin
 for USB


Hi Chanwoo,

On Wed, 2015-05-27 at 21:15 +0900, Chanwoo Choi wrote:
> Previously, I discussed how to inform the changed state of both ID
> and VBUS pin for USB connector on patch-set[1].
> [1] https://lkml.org/lkml/2015/4/2/310
> 
> So, this patch adds the extcon_set_cable_line_state() function to inform
> the additional state of external connectors without additional register/
> unregister functions. This function uses the existing notifier chain
> which is registered by extcon_register_notifier() / extcon_register_interest().
> 
> The extcon_set_cable_line_state() can inform the new state of both
> ID and VBUS pin state through extcon_set_cable_line_state().
> 
> For exmaple:
> - On extcon-usb-gpio.c as extcon provider driver as following:
>         static void usb_extcon_detect_cable(struct work_struct *work)
>         {
>                 ...
>                 /* check ID and update cable state */
>                 id = gpiod_get_value_cansleep(info->id_gpiod);
>                 if (id) {
>                         extcon_set_cable_state_(info->edev, EXTCON_USB_HOST, false);
>                         extcon_set_cable_state_(info->edev, EXTCON_USB, true);
> 
>                         extcon_set_cable_line_state(info->edev, EXTCON_USB,
>                                                         EXTCON_USB_ID_HIGH);

I am getting more and more confused :-). Why EXTCON_USB is now used for ID notifications?
It should be EXTCON_USB_HOST, no? Why we need another function, framework already have
required information from the function one line above, do I miss something?   

>                 } else {
>                         extcon_set_cable_state_(info->edev, EXTCON_USB, false);
>                         extcon_set_cable_state_(info->edev, EXTCON_USB_HOST, true);
> 
>                         extcon_set_cable_line_state(info->edev, EXTCON_USB,
>                                                         EXTCON_USB_ID_LOW);
>                 }
>         }
> 
> - On specific extcon consumder driver as following:
>         static int xxx_probe(struct platform_device *pdev)
>         {
>                 struct notifier_chain nh;
> 
>                 nb.notifier_call = extcon_usb_notifier;
>                 ret = extcon_register_notifier(edev, EXTCON_USB, &nb);

This is bit misleading. 'nb' could not be in stack.

Regards,
Ivan

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