9fans - fans of the OS Plan 9 from Bell Labs
 help / color / mirror / Atom feed
From: Richard Miller <9fans@hamnavoe.com>
To: 9fans@9fans.net
Subject: Re: [9fans] why is /dev/mousein exclusive use?
Date: Tue, 11 Dec 2012 15:30:13 +0000	[thread overview]
Message-ID: <45f52df340006f65d2c3f4142f9335bb@hamnavoe.com> (raw)
In-Reply-To: <59afe4dc4b5a632f46f77676a01350f5@coraid.com>

No objections having been raised, I've submitted a patch
(mousein-non-exclusive) to remove this restriction.

Next, the same question about /dev/kbin - does that need to be
exclusive open?  I think not.  Slightly more complicated, because
kbin can receive a pair of inputs (escape + scancode) and pass them
one at a time to the kbd driver.  But that is already a potential bug,
not prevented by exclusive open - usbd can start driver processes for
two usb keyboards, multiplexing their inputs through one fd to kbin,
and on a multiprocessor the escapes might be incorrectly interleaved.

My proposal is to remove the exclusive open, and instead put a qlock
around the loop which sends codes from kbin to kbd.




  parent reply	other threads:[~2012-12-11 15:30 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-12-10 16:36 Richard Miller
2012-12-10 16:38 ` erik quanstrom
2012-12-10 17:47   ` lucio
2012-12-11 15:30   ` Richard Miller [this message]
2012-12-11 15:45     ` erik quanstrom
2012-12-10 16:48 ` Anthony Martin

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=45f52df340006f65d2c3f4142f9335bb@hamnavoe.com \
    --to=9fans@hamnavoe.com \
    --cc=9fans@9fans.net \
    /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).