From: Maarten Brock <m.brock@vanmierlo.com>
To: "Måns Rullgård" <mans@mansr.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] serial: 8250: add option to disable registration of legacy ISA ports
Date: Thu, 18 Feb 2021 11:49:42 +0100 [thread overview]
Message-ID: <e0ac606ecc9f116f41fe4fccbf67a6bb@vanmierlo.com> (raw)
In-Reply-To: <yw1xwnvtcki0.fsf@mansr.com>
On 2021-01-31 14:18, Måns Rullgård wrote:
>> What userspace visable change will be caused by this?
>
> There won't be /dev/ttyS devices for ports that don't exist.
Oh yes, please!
That would mean I can create ttyS2 and upward while keeping ttyPS0 and
ttyPS1 (which invaded the serial<N> alias namespace) at the lower
numbers.
>> Will ports get renumbered?
>
> Not if they had predictable numbers to begin with.
It is hard to make predictable numbers with the backward operating
serial<N> aliases in the device tree. It makes relations in the wrong
direction.
If a system has two ttyPS<N> uarts (xilinx_uartps) and needs them at
ttyPS0 and ttyPS1 (or at least <=ttyPS9, due to another bug in
start_getty) and 10 ttyS<N> (8250) you can configure the kernel for 10
8250 devices and give 8 of them the predictable ttyS2 to ttyS9. The last
two will get the remaining ttyS0 and ttyS1. You cannot assign them their
number, because the serial0 and serial1 alias are required for the
ttyPS0 and ttyPS1.
However with this option it would be possible to configure for 12 8250
devices and not use nor see ttyS0 and ttyS1.
The best option would of course be to not even instantiate kernel
drivers for non-existing devices.
Maarten
prev parent reply other threads:[~2021-02-18 13:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-28 17:22 [PATCH] serial: 8250: add option to disable registration of legacy ISA ports Mans Rullgard
[not found] ` <CAHp75VenDC0R3uX4_=Yzii-q5Z-YWcfT2_OO0yJkYehYAHDCew@mail.gmail.com>
2021-01-31 19:47 ` Måns Rullgård
2021-02-01 7:38 ` Greg Kroah-Hartman
[not found] ` <YBam2m2VMowH5Yth@kroah.com>
[not found] ` <yw1xwnvtcki0.fsf@mansr.com>
[not found] ` <YBa0J82FrD6mdP/v@kroah.com>
2021-01-31 15:47 ` Måns Rullgård
2021-01-31 15:53 ` Greg Kroah-Hartman
2021-02-18 10:49 ` Maarten Brock [this message]
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