linux-kernel - Re: [PATCH v2] usb: core: introduce per-port over-current counters

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Date:   Tue, 20 Feb 2018 13:55:54 +0200
From:   Felipe Balbi <felipe.balbi@...ux.intel.com>
To:     Richard Leitner <dev@...l1n.net>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, stern@...land.harvard.edu,
        linux@...ck-us.net, mathias.nyman@...ux.intel.com,
        johan@...nel.org, ekorenevsky@...il.com, peter.chen@....com,
        drake@...lessm.com, joe@...ches.com,
        Richard Leitner <richard.leitner@...data.com>
Subject: Re: [PATCH v2] usb: core: introduce per-port over-current counters


Hi,

Richard Leitner <dev@...l1n.net> writes:
> From: Richard Leitner <richard.leitner@...data.com>
>
> For some userspace applications information on the number of
> over-current conditions at specific USB hub ports is relevant.
>
> In our case we have a series of USB hardware (using the cp210x driver)
> which communicates using a proprietary protocol. These devices sometimes
> trigger an over-current situation on some hubs. In case of such an
> over-current situation the USB devices offer an interface for reducing
> the max used power. As these conditions are quite rare and imply
> performance reductions of the device we don't want to reduce the max
> power always.
>
> Therefore give user-space applications the possibility to react
> adequately by introducing an over_current_counter in the usb port struct
> which is exported via sysfs.

why don't you just provide more than one configuration with several
bMaxPower fields? Then host OS should choose correct configuration based
on power budget.

-- 
balbi