From: Jiri Slaby <jirislaby@kernel.org>
To: Mychaela Falconia <mychaela.falconia@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Maarten Brock <m.brock@vanmierlo.com>,
Johan Hovold <johan@kernel.org>,
"Mychaela N . Falconia" <falcon@freecalypso.org>,
linux-serial@vger.kernel.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/7] tty: add flag to suppress ready signalling on open
Date: Fri, 11 Dec 2020 09:46:54 +0100 [thread overview]
Message-ID: <54f40116-9a11-8daa-d3cd-5557cc60a4ef@kernel.org> (raw)
In-Reply-To: <CA+uuBqaNcKadyLRyufm+6HUHXcs7o0rtgw84BrHc7Jq9PauV8Q@mail.gmail.com>
On 10. 12. 20, 19:59, Mychaela Falconia wrote:
>> O_DIRECT is an interesting hack, has anyone seen if it violates the
>> posix rules for us to use it on a character device like this?
>
> According to open(2) Linux man page, O_DIRECT does not come from POSIX
> at all, instead it is specific to Linux, FreeBSD and SGI IRIX. Thus
> it seems like there aren't any POSIX rules to be violated here.
>
> If we go with O_DIRECT, what semantics are we going to implement?
> There are 3 possibilities that come to mind most readily:
>
> 1) O_DIRECT applies only to the open call in which this flag is set,
> and suppresses DTR/RTS assertion on that open. If someone needs to do
> multiple opens with DTR/RTS suppression being required every time,
> then they need to include O_DIRECT every time.
>
> 2) O_DIRECT applies not only immediately, but also sets a latched flag
> whereby all subsequent opens continue to suppress auto-assertion
> without requiring O_DIRECT every time. This approach by itself runs
> counter to the generic Unix way of doing things, but it may be OK if
> there is also some ioctl to explicitly set or clear the latched flag.
>
> 3) O_DIRECT applies only to the open call in which it is set, no
> built-in latching, but there is also some ioctl to control a flag
> enabling or disabling DTR/RTS auto-assertion on subsequent opens.
3) -- to allow standard tools to work on the device after the quirk is
set up once.
thanks,
--
js
next prev parent reply other threads:[~2020-12-11 8:48 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-02 11:39 [PATCH v2 0/7] tty: add flag to suppress ready signalling on open Johan Hovold
2020-12-02 11:39 ` [PATCH v2 1/7] tty: use assign_bit() in port-flag accessors Johan Hovold
2020-12-02 11:39 ` [PATCH v2 2/7] tty: use const parameters " Johan Hovold
2020-12-02 11:39 ` [PATCH v2 3/7] tty: add port flag to suppress ready signalling on open Johan Hovold
2020-12-02 11:39 ` [PATCH v2 4/7] serial: core: add sysfs attribute " Johan Hovold
2020-12-02 11:39 ` [PATCH v2 5/7] USB: serial: " Johan Hovold
2020-12-02 11:39 ` [PATCH v2 6/7] USB: serial: ftdi_sio: pass port to quirk port_probe functions Johan Hovold
2020-12-02 11:39 ` [PATCH v2 7/7] USB: serial: ftdi_sio: add support for FreeCalypso DUART28C adapter Johan Hovold
2020-12-02 18:07 ` [PATCH v2 0/7] tty: add flag to suppress ready signalling on open Mychaela Falconia
2020-12-03 9:21 ` Johan Hovold
2020-12-09 14:30 ` Greg Kroah-Hartman
2020-12-09 15:10 ` Johan Hovold
2020-12-09 22:49 ` Mychaela Falconia
2020-12-10 9:06 ` Greg Kroah-Hartman
2020-12-10 10:41 ` Maarten Brock
2020-12-10 10:50 ` Greg Kroah-Hartman
2020-12-10 12:05 ` Maarten Brock
2020-12-10 13:01 ` Greg Kroah-Hartman
2020-12-10 18:59 ` Mychaela Falconia
2020-12-11 8:46 ` Jiri Slaby [this message]
2020-12-11 16:08 ` Greg Kroah-Hartman
2020-12-11 15:51 ` Maarten Brock
2020-12-11 16:08 ` Greg Kroah-Hartman
2020-12-14 14:21 ` Johan Hovold
2020-12-18 18:03 ` Mychaela Falconia
2021-01-07 15:25 ` Greg Kroah-Hartman
[not found] ` <YBPxG+i/ZLP8/wg1@hovoldconsulting.com>
2021-01-31 0:18 ` Mychaela Falconia
2021-01-31 5:24 ` Greg Kroah-Hartman
2020-12-11 10:46 ` Johan Hovold
2020-12-11 10:41 ` Johan Hovold
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=54f40116-9a11-8daa-d3cd-5557cc60a4ef@kernel.org \
--to=jirislaby@kernel.org \
--cc=falcon@freecalypso.org \
--cc=gregkh@linuxfoundation.org \
--cc=johan@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=m.brock@vanmierlo.com \
--cc=mychaela.falconia@gmail.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
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).