Re: finding out the attached device current requirement

[Pavan Kondeti <pkondeti@codeaurora.org>]

On 3/3/2011 3:15 PM, Felipe Balbi wrote:
> On Thu, Mar 03, 2011 at 02:22:34PM +0530, Pavan Kondeti wrote:
>> Hi
>>
>> I am adding ACA (Accessory Charger Adapter) detection support for MSM
>> OTG driver. Battery charging spec introduced ACA to facilitate charging
>> when acting as a host. The host does not have to supply power on VBUS
>> when ACA is connected. Host device can also draw some amount of current.
>> The amount of current is determined by subtracting the attached
>> peripheral current requirement from the charger rating current. I am
>> looking for a way to find out the attached peripheral's current
>> requirement. We already DEVICE_ADD and DEVICE_REMOVE notifications. But
> 
> bMaxPower from the device descriptor ??
> 
You are referring to bMaxPower in Configuration descriptor right? When a
multi configuration device is connected, configuration can be changed by
user at any time. The same can also be possible with a user claimed
port. So I am looking for a notification from USB core when a
SET_CONFIGURATION request is sent to a device connected on the root hub.
I will reduce my power (ACA rating current - bMaxpower of the config
being selected) upon this notification.

Thanks,
Pavan

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