Date: Thu, 24 May 2018 12:01:19 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Edward Napierala <trasz@freebsd.org>, "H. Schmalzbauer - OmniLAN" <h.schmalzbauer@omnilan.de> Cc: Ravi Pokala <rpokala@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r334115 - in head: share/man/man4 sys/dev/usb/template Message-ID: <94801dec-73b4-63f3-6f01-b0e175073d6e@selasky.org> In-Reply-To: <CAFLM3-r2VmtjeSOe6bPJ1kPumvY=GRRm45s5kQ88s3zXv-cH3Q@mail.gmail.com> References: <201805232006.w4NK64jS044384@repo.freebsd.org> <9B0033E1-56EC-4CA0-BC28-056871B32B0A@panasas.com> <fa8a13c4-c1ed-0b23-6c2e-3e23ecfe8137@omnilan.de> <CAFLM3-r2VmtjeSOe6bPJ1kPumvY=GRRm45s5kQ88s3zXv-cH3Q@mail.gmail.com>
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On 05/24/18 11:59, Edward Napierala wrote: > 2018-05-24 8:41 GMT+01:00 H. Schmalzbauer - OmniLAN < > h.schmalzbauer@omnilan.de>: > >> Am 23.05.2018 um 22:35 schrieb Ravi Pokala: >> >>> Hi Traz, >>> >>> You're referring to power consumption in terms of (milli)Amps. That's not >>> right; power is measured in Watts. What you're actually talking about is >>> *current*. And it looks like in some situations USB devices can draw more >>> than 500mA. >>> >> >> Since the voltage isn't a variable when talking about USB power, speaking >> of "power" while refering to current seems valid to me – it's 5 V only and >> those who read that don't even need to do any math in head. >> I never read 2500mW in USB world, 500mA is common. >> Just my 2¢ >> > > I've just did some googling, and it seems you're right - while from physics > point of view mA is definitely current and not power, pretty much > everywhere I look the USB power (reported in bMaxPower) is specified in mA, > not mW. Thus, I'm leaning toward leaving it as it is - wrong from a > physics point of view, but aligned with the the USB naming convention. > Even though implict, we could specify mA at 5Volt in the sysctl description. --HPS
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