[U-Boot] [PATCH 1/8] usb: gadget: Move CONFIG_USB_GADGET_VBUS_DRAW to Kconfig

Marek Vasut
2016-04-05T19:45:27Z

On 04/05/2016 07:35 PM, Stephen Warren wrote:
> On 04/05/2016 10:36 AM, Semen Protsenko wrote:
>> From: Sam Protsenko <semen.protsenko@linaro.org>
>>
>> The description was borrowed from kernel, but allowed range was changed
>> from 2..500 to 0..500, because some boards require this option to be 0.
>
> Do they /require/ the value to be 0, or simply currently have it set to
> 0 because whoever set the value in U-Boot wasn't aware that a value of 0
> could cause issues with some hosts?
>
> I'd be tempted to keep the same range as the Linux kernel and bump all
> boards up to a minimum value of 2.

Right. VBUS draw 0 might confuse some non-Linux systems.

> Presumably there's some good reason
> the kernel chose a minimum of 2, and in practice I expect increasing all
> boards to 2 isn't going to make any negative difference.
>
>> diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
>
>> +config USB_GADGET_VBUS_DRAW
>> + int "Maximum VBUS Power usage (2-500 mA)"
>> + range 0 500
>> + default 2
>> + help
>> + Some devices need to draw power from USB when they are
>> + configured, perhaps to operate circuitry or to recharge
>> + batteries. This is in addition to any local power supply,
>> + such as an AC adapter or batteries.
>> +
>> + Enter the maximum power your device draws through USB, in
>> + milliAmperes. The permitted range of values is 2 - 500 mA;
>> + 0 mA would be legal, but can make some hosts misbehave.
>
> In particular, I'm thinking of that last sentence.

--
Best regards,
Marek Vasut