linux-wireless.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Johannes Berg <johannes@sipsolutions.net>
To: Takashi Iwai <tiwai@suse.de>
Cc: Emmanuel Grumbach <emmanuel.grumbach@intel.com>,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: systemd-rfkill regression on 5.11 and later kernels
Date: Thu, 18 Mar 2021 12:16:54 +0100	[thread overview]
Message-ID: <9db9d9ae751a50c9fd1da1ee3bd4c564546ce1c5.camel@sipsolutions.net> (raw)
In-Reply-To: <s5hczvwiumf.wl-tiwai@suse.de>

On Thu, 2021-03-18 at 12:11 +0100, Takashi Iwai wrote:
> > That said, we can "fix" this like this, and hope we'll not get this
> > again? And if we do get it again ... well, we keep renaming the structs
> > and add "struct rfkill_event_v3" next time?
> 
> Yeah, that's a dilemma.  An oft-seen trick is to add more bytes for
> the future use, e.g. extend to 16 bytes and fill 0 for the remaining.

Yeah, I guess I could stick a reserved[15] there, it's small enough.

> In the sound driver, we introduced an ioctl to inform from user-space
> which API protocol it can speak, and the kernel falls back to the old
> API/ABI if it's a lower version or it's not told at all.  But I'm not
> sure whether such an implementation is optimal for rfkill.

I thought about it, but it ... doesn't really help.

Somebody's going to do

	ioctl(..., sizeof(ev)) == sizeof(ev)

and break on older kernels, or == my_fixed_size, or ... something. It's
not really going to address the issue entirely.

And it's more complexity.

johannes


  reply	other threads:[~2021-03-18 11:17 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-18  8:27 systemd-rfkill regression on 5.11 and later kernels Takashi Iwai
2021-03-18  9:26 ` Emmanuel Grumbach
2021-03-18  9:36 ` Johannes Berg
2021-03-18 10:07   ` Takashi Iwai
2021-03-18 10:50     ` Johannes Berg
2021-03-18 11:11       ` Takashi Iwai
2021-03-18 11:16         ` Johannes Berg [this message]
2021-03-19 22:15           ` Johannes Berg

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=9db9d9ae751a50c9fd1da1ee3bd4c564546ce1c5.camel@sipsolutions.net \
    --to=johannes@sipsolutions.net \
    --cc=emmanuel.grumbach@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-wireless@vger.kernel.org \
    --cc=tiwai@suse.de \
    /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).