linux-kernel - Re: [PATCH v2 10/17] compat_ioctl: remove translation for sound ioctls

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Date:   Thu, 13 Sep 2018 15:37:29 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "Arnd Bergmann" <arnd@...db.de>
Cc:     <viro@...iv.linux.org.uk>, "Jeff Dike" <jdike@...toit.com>,
        <alsa-devel@...a-project.org>,
        "Mauro Carvalho Chehab" <mchehab+samsung@...nel.org>,
        <linux-um@...ts.infradead.org>,
        "Richard Weinberger" <richard@....at>,
        "Jaroslav Kysela" <perex@...ex.cz>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 10/17] compat_ioctl: remove translation for sound ioctls

On Wed, 12 Sep 2018 17:13:02 +0200,
Arnd Bergmann wrote:
> 
> The SNDCTL_* and SOUND_* commands are the old OSS user interface.
> 
> I checked all the sound ioctl commands listed in fs/compat_ioctl.c
> to see if we still need the translation handlers. Here is what I
> found:
> 
> - sound/oss/ is (almost) gone from the kernel, this is what actually
>   needed all the translations
> - The ALSA emulation for OSS correctly handles all compat_ioctl
>   commands already.
> - sound/oss/dmasound/ is the last holdout of the original OSS code,
>   this is only used on arch/m68k, which has no 64-bit mode and
>   hence needs no compat handlers
> - arch/um/drivers/hostaudio_kern.c may run in 64-bit mode with
>   32-bit x86 user space underneath it. This rare corner case is
>   the only one that still needs the compat handlers.
> 
> By adding a simple redirect of .compat_ioctl to .unlocked_ioctl in the
> UML driver, we can remove all the COMPATIBLE_IOCTL() annotations without
> a change in functionality. For completeness, I'm adding the same thing
> to the dmasound file, knowing that it makes no difference.
> 
> The compat_ioctl list contains one comment about SNDCTL_DSP_MAPINBUF and
> SNDCTL_DSP_MAPOUTBUF, which actually would need a translation handler
> if implemented. However, the native implementation just returns -EINVAL,
> so we don't care.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Looks good to me.

Reviewed-by: Takashi Iwai <tiwai@...e.de>


thanks,

Takashi