On Tue, Jan 21, 2025 at 10:19:08PM +0530, Prashanth K wrote: > > > On 21-01-25 08:36 pm, Alan Stern wrote: > > On Tue, Jan 21, 2025 at 09:50:08AM +0530, Prashanth K wrote: > >> > >> > >> On 20-01-25 08:17 pm, Alan Stern wrote: > >>> On Mon, Jan 20, 2025 at 04:47:02PM +0530, Prashanth K wrote: > >>>> Currently CONFIG_USB_GADGET_VBUS_DRAW limits the maximum current > >>>> drawn from Vbus to be up to 500mA. However USB gadget operating > >>>> in SuperSpeed or higher can draw up to 900mA. Also, MaxPower in > >>>> ConfigFS takes its default value from this config. Hence increase > >>>> the allowed range of CONFIG_USB_GADGET_VBUS_DRAW to 900mA. > >>> > >>> Is this the sort of thing that really needs to be a Kconfig option? Why > >>> not make the decision at runtime, based on the needs of the gadget or > >>> function drivers and the connection speed? > >>> > >>> Alan Stern > >>> > >> > >> Right, set_config() in composite.c does this in runtime based on the > >> values of MaxPower (from configFS), VBUS_DRAW defconfig and speed. > >> If we don't set MaxPower from configFS, this config helps to set it > >> during compile time. In fact MaxPower in configFS takes its default > >> value from CONFIG_USB_GADGET_VBUS_DRAW . Sent this patch because Kconfig > >> has this limitation where it's only allowing values upto 500mA. > > > > Why does MaxPower need to be set at compile time? Why not set it at > > runtime instead? > > > > If MaxPower gets set at runtime then it can take its default value to be > > 500 mA or 900 mA depending on the connection speed. There will be no > > need for CONFIG_USB_GAGDGET_VBUS_DRAW. > > > > Yes, agreed. Can we mark CONFIG_USB_GAGDGET_VBUS_DRAW as legacy and > maybe also avoid configfs/composite from using it? Indeed, the whole idea is to avoid using CONFIG_USB_GADGET_VBUS_DRAW in configfs and composite. If nothing will still be using it, just remove it entirely. No need to mark it as legacy. Alan Stern
