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From: Oliver Neukum <>
To: Johan Hovold <>,
	Greg Kroah-Hartman <>
	Anthony Mallet <>,
Subject: Re: [PATCH v2 1/3] Revert "USB: cdc-acm: fix rounding error in TIOCSSERIAL"
Date: Thu, 08 Apr 2021 15:31:49 +0200
Message-ID: <> (raw)
In-Reply-To: <>

Am Donnerstag, den 08.04.2021, 15:16 +0200 schrieb Johan Hovold:
> This reverts commit b401f8c4f492cbf74f3f59c9141e5be3071071bb.
> The offending commit claimed that trying to set the values reported back
> by TIOCGSERIAL as a regular user could result in an -EPERM error when HZ
> is 250, but that was never the case.
> With HZ=250, the default 0.5 second value of close_delay is converted to
> 125 jiffies when set and is converted back to 50 centiseconds by
> TIOCGSERIAL as expected (not 12 cs as was claimed, even if that was the
> case before an earlier fix).
> Comparing the internal current and new jiffies values is just fine to
> determine if the value is about to change so drop the bogus workaround
> (which was also backported to stable).
> For completeness: With different default values for these parameters or
> with a HZ value not divisible by two, the lack of rounding when setting
> the default values in tty_port_init() could result in an -EPERM being
> returned, but this is hardly something we need to worry about.
> Cc: Anthony Mallet <>
> Cc:
> Signed-off-by: Johan Hovold <>
Acked-by: Oliver Neukum <>

  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-08 13:15 [PATCH v2 0/3] TIOCSSERIAL fixes Johan Hovold
2021-04-08 13:16 ` [PATCH v2 1/3] Revert "USB: cdc-acm: fix rounding error in TIOCSSERIAL" Johan Hovold
2021-04-08 13:31   ` Oliver Neukum [this message]
2021-04-08 13:16 ` [PATCH v2 2/3] USB: cdc-acm: fix unprivileged TIOCCSERIAL Johan Hovold
2021-04-08 13:32   ` Oliver Neukum
2021-04-08 13:16 ` [PATCH v2 3/3] USB: cdc-acm: fix TIOCGSERIAL implementation Johan Hovold
2021-04-08 13:33   ` Oliver Neukum

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