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From: Johan Hovold <johan@kernel.org>
To: Anthony Mallet <anthony.mallet@laas.fr>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Oliver Neukum <oneukum@suse.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH 1/3] Revert "USB: cdc-acm: fix rounding error in TIOCSSERIAL"
Date: Wed, 7 Apr 2021 13:25:45 +0200
Message-ID: <YG2WuTPjPhLPR/v7@hovoldconsulting.com> (raw)
In-Reply-To: <24685.37311.759816.776098@gargle.gargle.HOWL>

On Wed, Apr 07, 2021 at 01:04:31PM +0200, Anthony Mallet wrote:
> On Wednesday  7 Apr 2021, at 12:28, Johan Hovold wrote:
> > 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).
> 
> It was "12" (instead of 50) because the conversion gor TIOCGSERIAL was
> initially broken, and that was fixed in the previous commit
> 633e2b2ded739a34bd0fb1d8b5b871f7e489ea29

Right, so this patch is still just broken. The missing jiffies
conversion had already been added.

> > 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.
> 
> The -EPERM is harmful when a regular user wants to update other
> members of serial_struct without changing the close delays,
> e.g. ASYNC_LOW_LATENCY, which is granted to regular users.

You're missing the point; -EPERM will *not* be returned -- and this
patch was never needed.

Johan

  reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-07 10:28 [PATCH 0/3] USB: cdc-acm: TIOCSSERIAL fixes Johan Hovold
2021-04-07 10:28 ` [PATCH 1/3] Revert "USB: cdc-acm: fix rounding error in TIOCSSERIAL" Johan Hovold
2021-04-07 11:04   ` Anthony Mallet
2021-04-07 11:25     ` Johan Hovold [this message]
2021-04-07 10:28 ` [PATCH 2/3] USB: cdc-acm: fix unprivileged TIOCCSERIAL Johan Hovold
2021-04-08  7:48   ` Oliver Neukum
2021-04-08  9:42     ` Johan Hovold
2021-04-08 11:35       ` Oliver Neukum
2021-04-07 10:28 ` [PATCH 3/3] USB: cdc-acm: fix TIOCGSERIAL implementation Johan Hovold
2021-04-08  8:36   ` Oliver Neukum
2021-04-08  9:48     ` Johan Hovold
2021-04-08 11:34       ` Oliver Neukum
2021-04-08 11:54         ` Johan Hovold
2021-04-08 11:59           ` Oliver Neukum
2021-04-08 12:07             ` Greg Kroah-Hartman

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