On Wed, Feb 25, 2015 at 09:28:36PM +0800, zhangfei wrote:

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+static void hi6220_detect_work(struct work_struct *work)
+{
+	struct hi6220_priv *priv =
+		container_of(work, struct hi6220_priv, work.work);
+	int gpio_id, gpio_vbus;
+	enum usb_otg_state state;
+
+	if (!gpio_is_valid(priv->gpio_id) || !gpio_is_valid(priv->gpio_vbus))
+		return;
+
+	gpio_id = gpio_get_value_cansleep(priv->gpio_id);
+	gpio_vbus = gpio_get_value_cansleep(priv->gpio_vbus);

looks like this should be using extcon

Not used extcon before.
However, we need gpio_vbus interrupt.
Checked phy-tahvo.c and phy-omap-otg.c, not find extcon related with
interrupt.
Will investigate tomorrow.

drivers/extcon/extcon-gpio.c

I think there is no need to use extcon, gpio is clear enough.
extcon-gpio.c even do not support dt.

well, add DT. The whole idea of free software is that we improve on
things we already have. EXTCON is *the* API to handle such things.

I think I am still not understanding extcon-gpio, not sure why need
use this API here.

because extcon is the API to use for external connectors. The same way
you use regulator framework to control that single GPIO tied to an
enable signal of a fixed regulator, you use extcon when you need to read
that gpio signal tied to id pin of the USB connector.

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Here two gpio requires, one gpio as interrupt, in the interrupt
handler, we detect the gpio status judging the otg status.
extcon-gpio.c use the interrupt, then can we also use the gpio
interrupt.  Using extcon-gpio is used for saving gpio_request?

extcon is used to hide gpio_request from dwc2. dwc2 only knows about
extcon, not gpios. extcon will request the gpio and use it as interrupt
source. When an IRQ fires, it will read the gpio state and decide if it
should broadcast a message to tell dwc2 to become host or peripheral.

Thanks for the kind education, understand now.

hey, no problem ;-)

-- 
balbi