[PATCH 1/1] uboot-pcf50633-default-curr-lim-1A.patch

Stefan Schmidt stefan at openmoko.org
Thu Feb 21 20:38:11 CET 2008


On Fri, 2008-02-22 at 03:06, Andy Green wrote:
> But every USB host I ever saw has current limit and high-side switch.
> So I don't expect to find these kind of hosts,

Well, then let me tell you a story that this is not so unproblematic
as you may think.

Some time ago I had problems with the onboard graphics card of my
current notebook, T40p so not really and old or cheap one.

The first thing, before anything else, the technican that arrived at
my place to replace the board, asked me was "What kind of USB devices
did you attach to this notebook?"

So we had a nice technical chat about the proeblems he see in his
day-by-day work about UЅB devices drawing to much power from the
controller. He explains that there are tons of cheap USB devices out
there that don't care about the spec. Sometimes only the controller
was broken, sometimes the whole board.

Of course there are ways to avoid such problems in hw on the
controller side. But what if the vendor liked to save one cent or had
this pragmatic approach that nothing bad will happen and the time
pressure got higher and higher... ;)

Stefan Schmidt
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