Re: [PATCH] ALSA: fireface: add field for the number of messages copied to user space

From: Takashi Iwai <tiwai@suse.de>
To: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Cc: alsa-devel@alsa-project.org
Subject: Re: [PATCH] ALSA: fireface: add field for the number of messages copied to user space
Date: Sat, 04 Feb 2023 09:36:00 +0100	[thread overview]
Message-ID: <878rhdn7yn.wl-tiwai@suse.de> (raw)
In-Reply-To: <Y92s/z+41aKOii/b@workstation>

On Sat, 04 Feb 2023 01:55:27 +0100,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> On Fri, Feb 03, 2023 at 05:22:40PM +0100, Takashi Iwai wrote:
> > On Thu, 02 Feb 2023 14:37:08 +0100,
> > Takashi Sakamoto wrote:
> > > 
> > > Current structure includes no field to express the number of messages
> > > copied to user space, thus user space application needs to information
> > > out of the structure to parse the content of structure.
> > > 
> > > This commit adds a field to express the number of messages copied to user
> > > space since It is more preferable to use self-contained structure.
> > > 
> > > Kees Cook proposed an idea of annotation for bound of flexible arrays
> > > in his future improvement for flexible-length array in kernel. The
> > > additional field for message count is suitable to the idea as well.
> > > 
> > > Reference: https://people.kernel.org/kees/bounded-flexible-arrays-in-c
> > > Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
> > 
> > Wouldn't changing this break the existing application that talks with
> > the older ABI?  Just to be sure...
> 
> You may well have the concern, indeed.
> 
> The structure is not exposed to user space yet, since it was added by a
> commit ab811cfffa9 ("ALSA: fireface: update UAPI for data of knob
> control"). It just exists in your (and mine) tree at present.

Ah I see, then that's OK, better to change now.
Applied now to for-next branch.

thanks,

Takashi