linux-kernel - Re: [PATCH v4 1/1] extcon: usb-gpio: Introduce gpio usb extcon driver

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Message-ID: <5506D675.8010006@ti.com>
Date:	Mon, 16 Mar 2015 15:11:17 +0200
From:	Roger Quadros <rogerq@...com>
To:	"Ivan T. Ivanov" <ivan.ivanov@...aro.org>
CC:	<cw00.choi@...sung.com>, <myungjoo.ham@...sung.com>,
	<balbi@...com>, <tony@...mide.com>, <nsekhar@...com>,
	<devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 1/1] extcon: usb-gpio: Introduce gpio usb extcon driver

Hi Ivan,

On 16/03/15 14:32, Ivan T. Ivanov wrote:
> Hi, 
> 
> On Mon, 2015-02-02 at 12:21 +0200, 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@...com>
>> ---
>> v4:
>> - got rid of id_irqwake flag. Fail if enable/disable_irq_wake() fails
>> - changed host cable name to "USB-HOST"
> 
> I am sorry that I am getting a bit little late into this.
> 
> Isn't supposed that we have to use strings defined in 
> const char extcon_cable_name[][]?
> 
> 
>> +
>> +/* List of detectable cables */
>> +enum {
>> +       EXTCON_CABLE_USB = 0,
>> +       EXTCON_CABLE_USB_HOST,
>> +
> 
> Same here: duplicated with enum extcon_cable_name
> 
>> +       EXTCON_CABLE_END,
>> +};
>> +
>> +static const char *usb_extcon_cable[] = {
>> +       [EXTCON_CABLE_USB] = "USB",
>> +       [EXTCON_CABLE_USB_HOST] = "USB-HOST",
>> +       NULL,
>> +};

I'm not exactly sure how else it is supposed to work if we
support only a subset of cables from the global extcon_cable_name[][].

>>
> 
> <snip>
> 
>> +
>> +static int usb_extcon_probe(struct platform_device *pdev)
>> +{
>>
> 
> <snip>
> 
>> +
>> +       ret = devm_request_threaded_irq(dev, info->id_irq, NULL,
>> +                                       usb_irq_handler,
>> +                                       IRQF_TRIGGER_RISING |
>> +                                       IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> 
> Shouldn't triggers be defined in DTS files?

Could be but we're sure that we always need the trigger for both rising/falling edges
in this case. So the usage is more appropriately decided from application point of view
rather than h/w point of view. h/w is generic GPIO.

cheers,
-roger
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