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

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Message-ID: <5565D01C.3060106@ti.com>
Date:	Wed, 27 May 2015 17:09:32 +0300
From:	Roger Quadros <rogerq@...com>
To:	Chanwoo Choi <cwchoi00@...il.com>, <linux-kernel@...r.kernel.org>
CC:	<r.baldyga@...sung.com>, <peter.chen@...escale.com>,
	<kishon@...com>, <balbi@...com>, <iivanov@...sol.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

Chanwoo,

On 27/05/15 15:15, 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);

Now that all USB line states can be captured by a single cable type
can we get rid of EXTCON_USB_HOST?

That way the extcon driver doesn't need to make any decisions as to
what mode we're in (host/cable) and this is best left to the USB driver.

cheers,
-roger

>                          extcon_set_cable_state_(info->edev, EXTCON_USB, true);
>
>                          extcon_set_cable_line_state(info->edev, EXTCON_USB,
>                                                          EXTCON_USB_ID_HIGH);
>                  } 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);
>                  ...
>          }
>
>          static int extcon_usb_notifier(struct notifier_block *self,
>                  unsigned long event, void *ptr)
>          {
>                  switch (event) {
>                  case EXTCON_DETACHED:
>                          printk("USB is detached\n");
>                          break;
>                  case EXTCON_ATTACHED:
>                          printk("USB is attached\n");
>                          break;
>
>                  case EXTCON_USB_ID_LOW:
>                          printk("USB's ID pin is low state\n");
>                          break;
>                  case EXTCON_USB_ID_HIGH:
>                          printk("USB's ID pin is high state\n");
>                          break;
>                  case EXTCON_USB_VBUS_LOW:
>                          printk("USB's VBUS pin is high state\n");
>                          break;
>                  case EXTCON_USB_VBUS_HIGH:
>                          printk("USB's VBUS pin is high state\n");
>                          break;
>                  default:
>                          return -EINVAL;
>                  };
>          }
>
> Changes from v1:
> - Use dev_warn() instead of dev_info() if set the same extcon_line_state value.
>
> Chanwoo Choi (2):
>    extcon: Add extcon_set_cable_line_state() to inform the additional state of external connectors
>    extcon: usb-gpio: Update the ID pin state of USB when cable state is changed
>
>   drivers/extcon/extcon-usb-gpio.c |  6 ++++
>   drivers/extcon/extcon.c          | 74 +++++++++++++++++++++++++++++++++++++++-
>   include/linux/extcon.h           | 24 +++++++++++++
>   3 files changed, 103 insertions(+), 1 deletion(-)
>
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