Re: [PATCH v3 1/7] extcon: usb-gpio: Introduce gpio usb extcon driver

[Chanwoo Choi <cw00.choi@samsung.com>]

Hi Roger,

On 01/28/2015 09:15 PM, Roger Quadros wrote:
> This driver observes the USB ID pin connected over a GPIO and
> updates the USB cable extcon states accordingly.
> 
> The existing GPIO extcon driver is not suitable for this purpose
> as it needs to be taught to understand USB cable states and it
> can't handle more than one cable per instance.
> 
> For the USB case we need to handle 2 cable states.
> 1) USB (attach/detach)
> 2) USB-Host (attach/detach)
> 
> This driver can be easily updated in the future to handle VBUS
> events in case it happens to be available on GPIO for any platform.
> 
> Signed-off-by: Roger Quadros <rogerq@ti.com>
> ---
> v3:
> - removed IRQF_NO_SUSPEND flag. Added IRQF_TRIGGER_RISING and
>   IRQF_TRIGGER_FALLING
> - Added disable_irq() to suspend() and enable_irq() to resume()
> 
>  .../devicetree/bindings/extcon/extcon-usb-gpio.txt |  18 ++
>  drivers/extcon/Kconfig                             |   7 +
>  drivers/extcon/Makefile                            |   1 +
>  drivers/extcon/extcon-usb-gpio.c                   | 233 +++++++++++++++++++++
>  4 files changed, 259 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
>  create mode 100644 drivers/extcon/extcon-usb-gpio.c
> 
> diff --git a/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
> new file mode 100644
> index 0000000..85fe6b0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
> @@ -0,0 +1,18 @@
> +USB GPIO Extcon device
> +
> +This is a virtual device used to generate USB cable states from the USB ID pin
> +connected to a GPIO pin.
> +
> +Required properties:
> +- compatible: Should be "linux,extcon-usb-gpio"
> +- id-gpio: gpio for USB ID pin. See gpio binding.
> +
> +Example:
> +	extcon_usb1 {
> +		compatible = "linux,extcon-usb-gpio";
> +		id-gpio = <&gpio6 1 GPIO_ACTIVE_HIGH>;
> +	}
> +
> +	&omap_dwc3_1 {
> +		extcon = <&extcon_usb1>;
> +	};
> diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
> index 6a1f7de..fd11536 100644
> --- a/drivers/extcon/Kconfig
> +++ b/drivers/extcon/Kconfig
> @@ -93,4 +93,11 @@ config EXTCON_SM5502
>  	  Silicon Mitus SM5502. The SM5502 is a USB port accessory
>  	  detector and switch.
>  
> +config EXTCON_USB_GPIO
> +	tristate "USB GPIO extcon support"
> +	select GPIOLIB
> +	help
> +	  Say Y here to enable GPIO based USB cable detection extcon support.
> +	  Used typically if GPIO is used for USB ID pin detection.
> +
>  endif # MULTISTATE_SWITCH
> diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
> index 0370b42..6a08a98 100644
> --- a/drivers/extcon/Makefile
> +++ b/drivers/extcon/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
>  obj-$(CONFIG_EXTCON_PALMAS)	+= extcon-palmas.o
>  obj-$(CONFIG_EXTCON_RT8973A)	+= extcon-rt8973a.o
>  obj-$(CONFIG_EXTCON_SM5502)	+= extcon-sm5502.o
> +obj-$(CONFIG_EXTCON_USB_GPIO)	+= extcon-usb-gpio.o
> diff --git a/drivers/extcon/extcon-usb-gpio.c b/drivers/extcon/extcon-usb-gpio.c
> new file mode 100644
> index 0000000..99a58b2
> --- /dev/null
> +++ b/drivers/extcon/extcon-usb-gpio.c
> @@ -0,0 +1,233 @@
> +/**
> + * drivers/extcon/extcon-usb-gpio.c - USB GPIO extcon driver
> + *
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
> + * Author: Roger Quadros <rogerq@ti.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/extcon.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_gpio.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +
> +#define USB_GPIO_DEBOUNCE_MS	20	/* ms */
> +
> +struct usb_extcon_info {
> +	struct device *dev;
> +	struct extcon_dev *edev;
> +
> +	struct gpio_desc *id_gpiod;
> +	int id_irq;
> +	bool id_irqwake;		/* ID wakeup enabled flag */
> +
> +	unsigned long debounce_jiffies;
> +	struct delayed_work wq_detcable;
> +};
> +
> +/* List of detectable cables */
> +enum {
> +	EXTCON_CABLE_USB = 0,
> +	EXTCON_CABLE_USB_HOST,
> +
> +	EXTCON_CABLE_END,
> +};
> +
> +static const char *usb_extcon_cable[] = {
> +	[EXTCON_CABLE_USB] = "USB",
> +	[EXTCON_CABLE_USB_HOST] = "USB-Host",

I'll use the defined name for extcon cable name as soon because 
it has potential isseu about the conflict of extcon cable name between subsystems.
So, I recommend to use a captical letter as "USB-HOST" instead of "USB-Host".
If other extcon driver don't use the captical letter, I'll fix it.

[snip]

Thanks,
Chanwoo Choi