Re: USB device just moves
- From: phil-news-nospam@xxxxxxxx
- Date: 18 Feb 2008 14:56:45 GMT
On Sun, 17 Feb 2008 13:32:29 +0100 Rainer Weikusat <rweikusat@xxxxxxxxxxx> wrote:
| Tim Roberts <timr@xxxxxxxxx> writes:
|> Eric <Scorpus@xxxxxxxxxxxxxx> wrote:
|>>USB must be polled at regular intervals,...
|>
|> Interrupt and isochronous pipes must be polled at regular intervals. Other
|> pipe types do not.
|
| Your first statements means nothing more than 'USB must be polled at
| regular intervals'. Assuming there are neither interrupt (unlikely)
| nor isosychronous endpoints active on any device connected to some
| USB, what is left would basically be bulk in- out out-pipes, which
| only need to be 'polled at regular intervals' if one actually wants to
| receive or transmit data over the USB. Therefore, the only USB not
| being 'polled at regular intervals' is one without used devices
| connected to ti.
|
| [...]
|
|> There is nothing inherently wrong with a polled, dedicated master/slave bus
|> design.
|
| There was nothing wrong with the various token-passing based LAN
| technologies people considered to be a good idea (more than) twenty
| years ago, either. But for some mysterious reason, they have basically
| completely disappeared from the market.
There were some things wrong. While they basically worked, they just did
not work quite as well as the collision avoidance method that won out.
And even it has progressed to being a star system (switched fabric).
|> It avoids all the problems of assigning a bus master or handling
|> collisions among multiple senders.
|
| And there were lots and lots of wrongs inherent in CSMA/CD networks,
| but again, for some mysterious reasons, they were cheap and worked
| well in practice. But they were invented at a time when putting all of
| the practically stupid 'intelligent design' into mass-produced and
| therefore cheap ICs wasn't even possible. That's why it took some
| twenty years of technical progress until the 'intelligent design'
| finally became the chance to again rise from its well-deserved grave,
| where it rather should have been rested until kingdom come.
Worked well in practice was the key. Sure, it was imperfect in design.
So was token passing. But so much LAN infrastructure now is switched
communications. The only "collisions" are trying to send to a switch
that has filled all its buffers.
| The PS/2-mouse connected to my computer at work is a true real-time
| capable device, ie it 'works' whenever I move it. The USB-mouse I have
| at home cannot do that: If it has been inactive for some time, there
| is a noticable delay between the time I try to use it again and the
| time it actually reacts.
|
| A design which needs lots of high-developed components which are
| literally busy doing nothing almost all of the time is stupid.
Yes.
| That it can be produced cheaply, given that the right proponents are
| pushing it and works 'good enough' doesn't make it any less stupid.
Almost anything can be made into a chip. So anything can eventually be
cheap to mass produce.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2008-02-18-0852@xxxxxxxx |
|------------------------------------/-------------------------------------|
.
- References:
- USB device just moves
- From: phil-news-nospam
- Re: USB device just moves
- From: Mike
- Re: USB device just moves
- From: phil-news-nospam
- Re: USB device just moves
- From: Eric
- Re: USB device just moves
- From: Tim Roberts
- Re: USB device just moves
- From: Rainer Weikusat
- USB device just moves
- Prev by Date: Re: Kernel Space to User Space Communication in 2.6
- Next by Date: Re: How to determine if running on a 32 or 64 bits kernel ?
- Previous by thread: Re: USB device just moves
- Next by thread: Re: USB device just moves
- Index(es):
Relevant Pages
|
