Linux-Media Archive on lore.kernel.org
 help / color / Atom feed
From: Takashi Sakamoto <o-takashi@sakamocchi.jp>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Oscar Carter <oscar.carter@gmx.com>,
	stable <stable@vger.kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Stefan Richter <stefanr@s5r6.in-berlin.de>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Clemens Ladisch <clemens@ladisch.de>,
	Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	kernel-hardening@lists.openwall.com,
	linux1394-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	alsa-devel@alsa-project.org,
	"Lev R . Oshvang ." <levonshe@gmail.com>
Subject: Re: [PATCH v2] firewire: Remove function callback casts
Date: Sat, 23 May 2020 16:58:54 +0900
Message-ID: <20200523075854.GA170441@workstation> (raw)
In-Reply-To: <20200523061033.GB3131938@kroah.com>

Hi Greg,

On Sat, May 23, 2020 at 08:10:33AM +0200, Greg KH wrote:
> On Fri, May 22, 2020 at 07:43:08PM +0200, Oscar Carter wrote:
> > Hi,
> > 
> > On Wed, May 20, 2020 at 03:16:24PM +0900, Takashi Sakamoto wrote:
> > > Hi,
> > >
> > > I'm an author of ALSA firewire stack and thanks for the patch. I agree with
> > > your intention to remove the cast of function callback toward CFI build.
> > >
> > > Practically, the isochronous context with FW_ISO_CONTEXT_RECEIVE_MULTICHANNEL
> > > is never used by in-kernel drivers. Here, I propose to leave current
> > > kernel API (fw_iso_context_create() with fw_iso_callback_t) as is.
> 
> If it's not used by anyone, why is it still there?  Can't we just delete
> it?

For this patchset, I followed to the theory to keep backward compatibility
when adding any change, and it's what I'd like to discuss.

The isoc context of multichannel mode is also available for userspace
applications, and libhinoko[1] uses it. In a point of backward
compatibility for userspace, we can't delete the mode.

(Practically, the mode is useful for the purpose of packet sniffing in
bus and helpful to my work for development of ALSA firewire stack[2].)

On the other hand, there's no unit driver to use the mode in upstream
kernel. It's unlikely to use the mode for unit driver since the mode is
not specific to unit functionality. In my opinion, it's reasonable to
lose backward compatibility slightly by hiding the multichannel mode
from in-kernel unit driver.

I'll post v2 patchset later and I'd like you to merge them if no
objections from the others for the loss of backward compatibility.

[1] https://github.com/takaswie/libhinoko
[2] https://mailman.alsa-project.org/pipermail/alsa-devel/2019-April/147862.html


Regards

Takashi Sakamoto

      reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 17:34 Oscar Carter
2020-05-20  6:16 ` Takashi Sakamoto
2020-05-22 17:43   ` Oscar Carter
2020-05-23  6:10     ` greg
2020-05-23  6:10     ` Greg KH
2020-05-23  7:58       ` Takashi Sakamoto [this message]

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=20200523075854.GA170441@workstation \
    --to=o-takashi@sakamocchi.jp \
    --cc=alsa-devel@alsa-project.org \
    --cc=clemens@ladisch.de \
    --cc=gregkh@linuxfoundation.org \
    --cc=keescook@chromium.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=levonshe@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux1394-devel@lists.sourceforge.net \
    --cc=mchehab@kernel.org \
    --cc=oscar.carter@gmx.com \
    --cc=perex@perex.cz \
    --cc=stable@vger.kernel.org \
    --cc=stefanr@s5r6.in-berlin.de \
    --cc=tiwai@suse.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

Linux-Media Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-media/0 linux-media/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-media linux-media/ https://lore.kernel.org/linux-media \
		linux-media@vger.kernel.org
	public-inbox-index linux-media

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-media


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git