Message-id: <57A28F8F.7010101@samsung.com>
Date:	Thu, 04 Aug 2016 09:42:55 +0900
From:	Chanwoo Choi <cw00.choi@...sung.com>
To:	Roger Quadros <rogerq@...com>, linux-kernel@...r.kernel.org,
	Felipe Balbi <balbi@...nel.org>
Cc:	myungjoo.ham@...sung.com, zyw@...k-chips.com, groeck@...omium.org,
	chanwoo@...nel.org, Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: Re: [PATCH v3 2/6] extcon: Add the support for extcon property
 according to extcon type

Hi Roger,

On 2016년 08월 03일 18:46, Roger Quadros wrote:
> Hi Chanwoo,
> 
> On 02/08/16 11:08, Chanwoo Choi wrote:
>> Hi,
>>
>> On 2016년 08월 02일 16:43, Roger Quadros wrote:
>>> +Felipe
>>>
>>> Hi,
>>>
>>> On 02/08/16 04:58, Chanwoo Choi wrote:
>>>> This patch support the extcon property for the external connector
>>>> because each external connector might have the property according to
>>>> the H/W design and the specific characteristics.
>>>>
>>>> - EXTCON_PROP_USB_[property name]
>>>> - EXTCON_PROP_CHG_[property name]
>>>> - EXTCON_PROP_JACK_[property name]
>>>> - EXTCON_PROP_DISP_[property name]
>>>>
>>>> Add the new extcon APIs to get/set the property value as following:
>>>> - int extcon_get_property(struct extcon_dev *edev, unsigned int id,
>>>> 			unsigned int prop,
>>>> 			union extcon_property_value *prop_val)
>>>> - int extcon_set_property(struct extcon_dev *edev, unsigned int id,
>>>> 			unsigned int prop,
>>>> 			union extcon_property_value prop_val)
>>>>
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
>>>> Tested-by: Chris Zhong <zyw@...k-chips.com>
>>>> Tested-by: Guenter Roeck <groeck@...omium.org>
>>>> Reviewed-by: Guenter Roeck <groeck@...omium.org>
>>>> ---
>>>>  drivers/extcon/extcon.c | 201 +++++++++++++++++++++++++++++++++++++++++++++++-
>>>>  include/linux/extcon.h  |  86 +++++++++++++++++++++
>>>>  2 files changed, 286 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
>>>> index 129afc87313e..bb6e99fe84c8 100644
>>>> --- a/drivers/extcon/extcon.c
>>>> +++ b/drivers/extcon/extcon.c
>>>> @@ -196,6 +196,11 @@ struct extcon_cable {
>>>>  	struct device_attribute attr_state;
>>>>  
>>>>  	struct attribute *attrs[3]; /* to be fed to attr_g.attrs */
>>>> +
>>>> +	union extcon_property_value usb_propval[EXTCON_PROP_USB_CNT];
>>>> +	union extcon_property_value chg_propval[EXTCON_PROP_CHG_CNT];
>>>> +	union extcon_property_value jack_propval[EXTCON_PROP_JACK_CNT];
>>>> +	union extcon_property_value disp_propval[EXTCON_PROP_DISP_CNT];
>>>>  };
>>>>  
>>>>  static struct class *extcon_class;
>>>> @@ -248,6 +253,27 @@ static int find_cable_index_by_id(struct extcon_dev *edev, const unsigned int id
>>>>  	return -EINVAL;
>>>>  }
>>>>  
>>>> +static int get_extcon_type(unsigned int prop)
>>>> +{
>>>> +	switch (prop) {
>>>> +	case EXTCON_PROP_USB_MIN ... EXTCON_PROP_USB_MAX:
>>>> +		return EXTCON_TYPE_USB;
>>>> +	case EXTCON_PROP_CHG_MIN ... EXTCON_PROP_CHG_MAX:
>>>> +		return EXTCON_TYPE_CHG;
>>>> +	case EXTCON_PROP_JACK_MIN ... EXTCON_PROP_JACK_MAX:
>>>> +		return EXTCON_TYPE_JACK;
>>>> +	case EXTCON_PROP_DISP_MIN ... EXTCON_PROP_DISP_MAX:
>>>> +		return EXTCON_TYPE_DISP;
>>>> +	default:
>>>> +		return -EINVAL;
>>>> +	}
>>>> +}
>>>> +
>>>> +static bool is_extcon_attached(struct extcon_dev *edev, unsigned int index)
>>>> +{
>>>> +	return !!(edev->state & BIT(index));
>>>> +}
>>>> +
>>>>  static bool is_extcon_changed(u32 prev, u32 new, int idx, bool *attached)
>>>>  {
>>>>  	if (((prev >> idx) & 0x1) != ((new >> idx) & 0x1)) {
>>>> @@ -258,6 +284,34 @@ static bool is_extcon_changed(u32 prev, u32 new, int idx, bool *attached)
>>>>  	return false;
>>>>  }
>>>>  
>>>> +static bool is_extcon_property_supported(unsigned int id, unsigned int prop)
>>>> +{
>>>> +	int type;
>>>> +
>>>> +	/* Check whether the property is supported or not. */
>>>> +	type = get_extcon_type(prop);
>>>> +	if (type < 0)
>>>> +		return false;
>>>> +
>>>> +	/* Check whether a specific extcon id supports the property or not. */
>>>> +	return !!(extcon_info[id].type & type);
>>>> +}
>>>> +
>>>> +static void init_property(struct extcon_dev *edev, unsigned int id, int index)
>>>> +{
>>>> +	unsigned int type = extcon_info[id].type;
>>>> +	struct extcon_cable *cable = &edev->cables[index];
>>>> +
>>>> +	if (EXTCON_TYPE_USB & type)
>>>> +		memset(cable->usb_propval, 0, sizeof(cable->usb_propval));
>>>> +	if (EXTCON_TYPE_CHG & type)
>>>> +		memset(cable->chg_propval, 0, sizeof(cable->chg_propval));
>>>> +	if (EXTCON_TYPE_JACK & type)
>>>> +		memset(cable->jack_propval, 0, sizeof(cable->jack_propval));
>>>> +	if (EXTCON_TYPE_DISP & type)
>>>> +		memset(cable->disp_propval, 0, sizeof(cable->disp_propval));
>>>> +}
>>>> +
>>>>  static ssize_t state_show(struct device *dev, struct device_attribute *attr,
>>>>  			  char *buf)
>>>>  {
>>>> @@ -421,7 +475,7 @@ int extcon_get_cable_state_(struct extcon_dev *edev, const unsigned int id)
>>>>  	if (edev->max_supported && edev->max_supported <= index)
>>>>  		return -EINVAL;
>>>>  
>>>> -	return !!(edev->state & (1 << index));
>>>> +	return is_extcon_attached(edev, index);
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(extcon_get_cable_state_);
>>>>  
>>>> @@ -449,12 +503,157 @@ int extcon_set_cable_state_(struct extcon_dev *edev, unsigned int id,
>>>>  	if (edev->max_supported && edev->max_supported <= index)
>>>>  		return -EINVAL;
>>>>  
>>>> +	/*
>>>> +	 * Initialize the value of extcon property before setting
>>>> +	 * the detached state for an external connector.
>>>> +	 */
>>>> +	if (!cable_state)
>>>> +		init_property(edev, id, index);
>>>> +
>>>
>>> I'm a bit concerned about this for USB case. See below why.
>>>
>>>>  	state = cable_state ? (1 << index) : 0;
>>>>  	return extcon_update_state(edev, 1 << index, state);
>>>>  }
>>>>  EXPORT_SYMBOL_GPL(extcon_set_cable_state_);
>>>>  
>>>>  /**
>>>> + * extcon_get_property() - Get the property value of a specific cable.
>>>> + * @edev:		the extcon device that has the cable.
>>>> + * @id:			the unique id of each external connector
>>>> + *			in extcon enumeration.
>>>> + * @prop:		the property id among enum extcon_property.
>>>> + * @prop_val:		the pointer which store the value of property.
>>>> + *
>>>> + * When getting the property value of external connector, the external connector
>>>> + * should be attached. If detached state, function just return 0 without
>>>> + * property value. Also, the each property should be included in the list of
>>>> + * supported properties according to the type of external connectors.
>>>> + *
>>>> + * Returns 0 if success or error number if fail
>>>> + */
>>>> +int extcon_get_property(struct extcon_dev *edev, unsigned int id,
>>>> +				unsigned int prop,
>>>> +				union extcon_property_value *prop_val)
>>>> +{
>>>> +	struct extcon_cable *cable;
>>>> +	unsigned long flags;
>>>> +	int index, ret = 0;
>>>> +
>>>> +	*prop_val = (union extcon_property_value)(0);
>>>> +
>>>> +	if (!edev)
>>>> +		return -EINVAL;
>>>> +
>>>> +	/* Check whether the property is supported or not */
>>>> +	if (!is_extcon_property_supported(id, prop))
>>>> +		return -EINVAL;
>>>> +
>>>> +	/* Find the cable index of external connector by using id */
>>>> +	index = find_cable_index_by_id(edev, id);
>>>> +	if (index < 0)
>>>> +		return index;
>>>> +
>>>> +	spin_lock_irqsave(&edev->lock, flags);
>>>> +
>>>> +	/*
>>>> +	 * Check whether the external connector is attached.
>>>> +	 * If external connector is detached, the user can not
>>>> +	 * get the property value.
>>>> +	 */
>>>
>>> How will this work for USB case? We need to know VBUS and ID states
>>> even if the USB cable is detached.
>>
>> When USB is detached, extcon_get_property return the default value without any operation.
>> The default value of supported property are 0 (zero). If new property need the differnt default
>> value, I'll support it.
> 
> Is the property a property of the connector or of the cable?
> 
> In my opinion, ID and VBUS are properties of the USB connector and not of
> the USB cable. So extcon must provide valid status for those properties
> even if USB cable or USB_HOST cable is detached.

I don't understand about that if USB and USB_HOST are detached,
how can the USB be operating? As you mentioned that, extcon must
provide the valid status for both state and properties. 

So, I already mentioned, When USB and USB_HOST are detached,
extcon return the default value instead of error value.
I think that it is reasonable. Why is it not a valid?

> 
> USB controller drivers are interested in raw VBUS and ID states
> irrespective of EXTCON_USB attached/detached or EXTCON_USB_HOST
> attached/detached state.

As I already mentioned about this issue, the extcon support the
two notification. One is notification to framework/device driver
in kernel-space. The second role send the uevent to user-space
to detect the type of connected external connector.

Firstly, extcon have to check the connected state of any external connector.
When there is no connected connector, extcon cannot check the both
state and property of external connector.

You want that the extcon split out the handling role of state and properties.
But it breaks the basically concept and method of extcon.

So, we need to find the good method to support the user-space and kernel-space
with extcon. Thanks for your comment.

Regards,
Chanwoo Choi

> 
> We don't want to have a window where both cables are in detached states
> and controller cannot get valid VBUS/ID properties.
>>
>>>
>>> Moreover there is no specific mechanism to detect if the USB cable is attached
>>> or not in the extcon-usb-gpio.c case.
>>> One solution could be to set EXTCON_USB as always attached on probe in extcon-usb-gpio.c.
>>>
>>> Is this acceptable?
>>
>> No. the extcon have to detect the correct state. When USB cable is detached, 
>> the extcon cannot set the attached state for EXTCON_USB.
>>
> 
> OK.
>>>
>>>> +	if (!is_extcon_attached(edev, index)) {
>>>> +		spin_unlock_irqrestore(&edev->lock, flags);
>>>> +		return 0;
>>>> +	}
>>>> +
>>>> +	cable = &edev->cables[index];
>>>> +
>>>> +	/* Get the property value according to extcon type */
>>>> +	switch (prop) {
>>>> +	case EXTCON_PROP_USB_MIN ... EXTCON_PROP_USB_MAX:
>>>> +		*prop_val = cable->usb_propval[prop - EXTCON_PROP_USB_MIN];
>>>> +		break;
>>>> +	case EXTCON_PROP_CHG_MIN ... EXTCON_PROP_CHG_MAX:
>>>> +		*prop_val = cable->chg_propval[prop - EXTCON_PROP_CHG_MIN];
>>>> +		break;
>>>> +	case EXTCON_PROP_JACK_MIN ... EXTCON_PROP_JACK_MAX:
>>>> +		*prop_val = cable->jack_propval[prop - EXTCON_PROP_JACK_MIN];
>>>> +		break;
>>>> +	case EXTCON_PROP_DISP_MIN ... EXTCON_PROP_DISP_MAX:
>>>> +		*prop_val = cable->disp_propval[prop - EXTCON_PROP_DISP_MIN];
>>>> +		break;
> 
> cheers,
> -roger
> 
> 
> 

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