LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: David Brownell <david-b@pacbell.net>
To: David Newall <davidn@davidnewall.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Greg KH <greg@kroah.com>,
	linux-usb@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Handshaking on USB serial devices
Date: Thu, 14 Feb 2008 10:53:55 -0800	[thread overview]
Message-ID: <200802141053.55914.david-b@pacbell.net> (raw)
In-Reply-To: <47B482B4.9010208@davidnewall.com>

On Thursday 14 February 2008, David Newall wrote:
> RS232 is (normally) so much slower than USB that, on an extended
> transmission, the buffer internal to the local hardware can fill well
> before the remote device has demanded that transmission stop.  In fact,
> now that you've mentioned it, I can't see that anything to stop the
> driver from overflowing the internal buffer, which is very perplexing. 
> Would that be right? 

Only for stupidly designed hardware ... which you might well
be using, though I happen to never have seen anything that's
quite *that* stupid.  (There's always a first time though.)

USB has enough control flow to prevent that from happening.
If the host sends data that the peripheral isn't ready to
accept, the peripheral just refuses to accept it, and the
host will retry later.

- Dave


  reply	other threads:[~2008-02-14 18:54 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-13 14:45 David Newall
2008-02-14  5:02 ` Greg KH
2008-02-14  9:25   ` David Newall
2008-02-14 12:10     ` Alan Cox
2008-02-14 16:16       ` Gene Heskett
2008-02-14 16:31         ` Alan Cox
2008-02-14 17:55           ` Gene Heskett
2008-02-14 19:37             ` Alan Cox
2008-02-14 20:04               ` Gene Heskett
2008-02-14 20:52                 ` Greg KH
2008-02-14 21:32                   ` Gene Heskett
2008-02-15  5:08               ` David Newall
2008-02-14 22:39         ` Krzysztof Halasa
2008-02-14 23:09           ` Gene Heskett
2008-02-14 18:04       ` David Newall
2008-02-14 18:53         ` David Brownell [this message]
2008-02-14 19:36         ` Alan Cox
2008-02-21 15:22           ` David Newall
2008-02-21 15:15             ` Alan Cox
2008-02-21 19:35               ` David Newall
2008-02-21 20:58                 ` Greg KH
2008-02-14 20:47     ` Greg KH
2008-02-15  5:19       ` David Newall
2008-02-14 11:55   ` Alan Cox
     [not found] <9Wr5Z-7cw-1@gated-at.bofh.it>
     [not found] ` <9WSJ4-222-21@gated-at.bofh.it>
     [not found]   ` <9WTlN-2T0-7@gated-at.bofh.it>
     [not found]     ` <9WTYn-3Zb-29@gated-at.bofh.it>
2008-02-15 12:00       ` Bodo Eggert

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=200802141053.55914.david-b@pacbell.net \
    --to=david-b@pacbell.net \
    --cc=alan@lxorguk.ukuu.org.uk \
    --cc=davidn@davidnewall.com \
    --cc=greg@kroah.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-usb@vger.kernel.org \
    --subject='Re: Handshaking on USB serial devices' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).