linux-kernel - Re: [PATCH] extcon: Add EXTCON_BATTERY type for battery presence

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Message-ID: <d2b63765-d497-8938-95f0-68d0cc4c2efd@gmail.com>
Date:   Mon, 30 Jan 2023 23:17:04 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Andrew Lien/WHQ/Wistron <Andrew_Lien@...tron.com>,
        "myungjoo.ham@...sung.com" <myungjoo.ham@...sung.com>
Cc:     "cw00.choi@...sung.com" <cw00.choi@...sung.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] extcon: Add EXTCON_BATTERY type for battery presence

On 23. 1. 11. 18:00, Andrew Lien/WHQ/Wistron wrote:
> Sorry I didn't describe it in detail enough
> 
> we have a standalone driver to do battery detection, this driver is separate from power_supply device driver
> and not just report uevet to userspace, we also need a method to notify other kernel driver "battery removal event"

As I commented, it is not good to detect the battery status by extcon
which only handle the external connector.
It means that you just try to use extcon subsystem to support 'publisher - subscriber'.


> it will be better if using same battery detection driver to support different platform charger driver.
> 
> by the way, swappable battery usually have 4 pin connector (power / ground / ID / THERMAL)
> you can find some phone that support battery swap feature (like Samsung xcover 6 pro)
> 
> -----Original Message-----
> From: Chanwoo Choi <cwchoi00@...il.com> 
> Sent: Tuesday, January 10, 2023 9:40 PM
> To: Andrew Lien/WHQ/Wistron <Andrew_Lien@...tron.com>; myungjoo.ham@...sung.com
> Cc: cw00.choi@...sung.com; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] extcon: Add EXTCON_BATTERY type for battery presence
> 
> On 23. 1. 10. 11:36, andrew lien/WHQ/Wistron wrote:
>> This information can be useful to device that support battery swap, 
>> for example allowing them to indicate that a battery is present or 
>> not, so provide a standard way to report it to userspace.
>>
>> Signed-off-by: andrew lien/WHQ/Wistron <andrew_lien@...tron.com>
>> ---
>>  drivers/extcon/extcon.c | 5 +++++
>>  include/linux/extcon.h  | 3 ++-
>>  2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c index 
>> b4df4372f097..6c47d23244c3 100644
>> --- a/drivers/extcon/extcon.c
>> +++ b/drivers/extcon/extcon.c
>> @@ -184,6 +184,11 @@ static const struct __extcon_info {
>>  		.id = EXTCON_MECHANICAL,
>>  		.name = "MECHANICAL",
>>  	},
>> +	[EXTCON_BATTERY] = {
>> +		.type = EXTCON_TYPE_MISC,
>> +		.id = EXTCON_BATTERY,
>> +		.name = "BATTERY",
>> +	},
>>  
>>  	{ /* sentinel */ }
>>  };
>> diff --git a/include/linux/extcon.h b/include/linux/extcon.h index 
>> b0b4abb018ee..88210b481b6c 100644
>> --- a/include/linux/extcon.h
>> +++ b/include/linux/extcon.h
>> @@ -81,8 +81,9 @@
>>  #define EXTCON_DOCK		60
>>  #define EXTCON_JIG		61
>>  #define EXTCON_MECHANICAL	62
>> +#define EXTCON_BATTERY		63
>>  
>> -#define EXTCON_NUM		63
>> +#define EXTCON_NUM		64
>>  
>>  /*
>>   * Define the properties of supported external connectors.
> 
> Actually, battery is not external connector. The power_supply subsystem already provided the POWER_SUPPLY_PROP_PRESENT for the battery present. You have to develop the power_supply device driver and then use power_supply_changed() to send the uevent to user-space.
> 
> --
> Best Regards,
> Samsung Electronics
> Chanwoo Choi
> 
> 
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-- 
Best Regards,
Samsung Electronics
Chanwoo Choi