linux-kernel - Re: [PATCH] cdrom: do not print info list when there is no cdrom device

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Date:   Sat, 9 Apr 2022 09:16:45 +0100
From:   Phillip Potter <phil@...lpotter.co.uk>
To:     Enze Li <lienze@...inos.cn>
Cc:     axboe@...nel.dk, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org
Subject: Re: [PATCH] cdrom: do not print info list when there is no cdrom
 device

On Sat, Apr 09, 2022 at 12:25:30PM +0800, Enze Li wrote:
> On Fri, 8 Apr 2022 06:34:04 -0600
> Jens Axboe <axboe@...nel.dk> wrote:
> 
> > On 4/8/22 2:42 AM, Enze Li wrote:
> > > There is no need to print a list of cdrom entries with blank info
> > > when no cdrom device exists.  With this patch applied, we get:
> > > 
> > > ================================================
> > > $ cat /proc/sys/dev/cdrom/info
> > > CD-ROM information, Id:cdrom.c 3.20 2003/12/17
> > > 
> > > No device found.
> > > 
> > > ================================================  
> 
> Hi Jens,
> 
> Thanks for your review.
> 
> > 
> > And what did we get before?
> 
> Without the patch, we get:
> 
> ================================================
> $ cat /proc/sys/dev/cdrom/info
> CD-ROM information, Id: cdrom.c 3.20 2003/12/17
> 
> drive name:	
> drive speed:	
> drive # of slots:
> Can close tray:	
> Can open tray:	
> Can lock tray:	
> Can change speed:
> Can select disk:
> Can read multisession:
> Can read MCN:	
> Reports media changed:
> Can play audio:	
> Can write CD-R:	
> Can write CD-RW:
> Can read DVD:	
> Can write DVD-R:
> Can write DVD-RAM:
> Can read MRW:	
> Can write MRW:	
> Can write RAM:	
> 
> 
> ================================================
> 
> > 
> > Will this potentially break applications that parse it?
> > 
> 
> I dunno, is there any way to confirm this thing?  And if this is really
> a possibility, does it mean that we cannot make changes?
> 
Sorry, anything that can be parsed from userspace has the potential to
break userspace applications. For that reason, I would have to say I
don't think this patch is suitable. Sure there are times it's
appropriate to change userspace interfaces, but I'd rather err on the
side of caution here. Thanks for the patch though.

Nacked-by: Phillip Potter <phil@...lpotter.co.uk>

Regards,
Phil