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Date:      Sun, 13 Feb 2000 04:13:19 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        "Jose M. Alcaide" <jose@we.lc.ehu.es>
Cc:        freebsd-hardware@FreeBSD.ORG, freebsd-mobile@FreeBSD.ORG
Subject:   Re: [fix and RFC] interrupt-level buffer overflows with Xircom PCMCIA modem
Message-ID:  <Pine.BSF.4.21.0002130354510.3031-100000@alphplex.bde.org>
In-Reply-To: <38A56AD6.8C3E1A97@we.lc.ehu.es>

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On Sat, 12 Feb 2000, Jose M. Alcaide wrote:

> Now, the conclusions: perhaps RS_IBUFSIZE=256 is too low for some devices
> (notably internal modems); it's only a theory. Or perhaps some devices

Too large for devices with broken 16550 emulation.

> have problems with RTS/CTS flow control. In any case, I suggest

RTS emulation is probably also broken for there to be a problem.  Ideally,
the sender should check its version of RTS (i.e., CTS) before sending
each character.  For bug for bug compatibility with 16550 senders, the
sender only needs to check it every 16th character.

> the addition of a new kernel configuration option for permitting
> to change RS_IBUFSIZE to any desired value.

RS_IBUFSIZE doesn't exist in -current.  Instead, the buffer is sized to
hold 4 ticks (4.0 / hz seconds) worth of input at the current input speed
(or 128 bytes if that is larger).

Bruce



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