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

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Date:	Tue, 17 Mar 2015 11:01:51 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	"Ivan T. Ivanov" <ivan.ivanov@...aro.org>
Cc:	Roger Quadros <rogerq@...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 03/16/2015 11:23 PM, Ivan T. Ivanov wrote:
> 
> Hi Roger, 
> 
> On Mon, 2015-03-16 at 15:11 +0200, Roger Quadros wrote:
>> 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[][].
> 
> I don't see issue that we use just 2 events. I think that we can
> reuse  enum extcon_cable_name and strings already defined in 
> extcon_cable_name[][] global variable. It is defined extern in
> extcon.h file exactly for this purpose, no?

'extcon_cable_name' global variable is not used on extcon driver directly.
It is just recommended cable name. 

I have plan to use standard cable name for extcon driver instead of that
each extcon driver define the cable name.

[snip]

Thanks,
Chanwoo Choi
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