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

Stephen Warren
2016-04-05T17:35:54Z

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. 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.