linux-kernel - Re: [RFC 5/5] i3c: add i3cdev module to expose i3c dev in /dev

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAK8P3a2vRG9uiY6jCRip98DHVP5-FeWk_sToGrPSA_WcY0agcA@mail.gmail.com>
Date:   Wed, 11 Dec 2019 16:33:24 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Vitor Soares <Vitor.Soares@...opsys.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        gregkh <gregkh@...uxfoundation.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [RFC 5/5] i3c: add i3cdev module to expose i3c dev in /dev

On Wed, Dec 11, 2019 at 4:07 PM Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> From: Arnd Bergmann <arnd@...db.de>
> Date: Tue, Dec 10, 2019 at 19:37:14
> > On Tue, Dec 10, 2019 at 8:15 PM Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> > > From: Arnd Bergmann <arnd@...db.de>
> > > Date: Tue, Dec 10, 2019 at 17:51:14
> > > > On Tue, Dec 10, 2019 at 4:37 PM Vitor Soares <Vitor.Soares@...opsys.com> wrote:
> > As your interface is basically just read/write based, I wonder
> > if there is a way to completely avoid the ioctl and instead
> > use io_submit() as the primary interface.
>
> I confess that I wasn't familiar with io_submit() until now and went
> straightway for the ioctl() approach.
> So far, my understanding is that io_submit() will call .write or .read of
> i3cdev module depending on the iocb command. if so, we won't be able to
> do a repeated start between a multiple iocb in the same list, right?

I'm not sure what you mean with "repeated start", but it's definitely
possible that io_submit() is not a useful interface for i3c. The main
advantage would be that it avoids creating a complex ioctl command.

> Apart from this private read/write need, another requirement that leads
> me to use the ioctl() was:
> - When we support HDR command in i3c subsystem we can expand the ioctl()
> command to support it.
> - For now, device API doesn't expose CCC commands but some of them are
> used for a private contract between master and device and we likely need
> that support in the future as well.

I think you could still have both the io_submit() interface for basic I/O
(if you can get it to do what you want), plus an ioctl interface for more
complex interactions.

     Arnd