linux-kernel - RE: [RESEND PATCH] serial: samsung: fix device name

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Message-id: <018a01cbb220$13145bb0$393d1310$%kim@samsung.com>
Date:	Wed, 12 Jan 2011 15:15:07 +0900
From:	Kukjin Kim <kgene.kim@...sung.com>
To:	'Darius Augulis' <augulis.darius@...il.com>,
	'Ben Dooks' <ben-linux@...ff.org>
Cc:	'Paulius Zaleckas' <paulius.zaleckas@...il.com>,
	linux-serial@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: RE: [RESEND PATCH] serial: samsung: fix device name

Darius Augulis wrote:
> 
> On Mon, Sep 27, 2010 at 3:18 AM, Ben Dooks <ben-linux@...ff.org> wrote:
> > On 24/09/10 17:37, Paulius Zaleckas wrote:
> >> On 09/24/2010 09:57 AM, Darius Augulis wrote:
> >>> Hi,
> >>>
> >>> On Fri, Sep 24, 2010 at 2:40 AM, Ben Dooks<ben-linux@...ff.org>
 wrote:
> >>>> On 23/09/10 20:15, Darius Augulis wrote:
> >>>>> Swap device and driver names in serial/samsung.c
> >>>>
> >>>> This is far too short, please see the notes below on trying
> >>>> to make this more informative.
> >>>>
> >>>>> Signed-off-by: Darius Augulis<augulis.darius@...il.com>
> >>>>> ---
> >>>>>
> >>>>> This patch was submitted about 3 months ago, but still not merged.
> >>>>> There was another similar patch from Joonyoung Shim
> >>>>> <jy0922.shim@...sung.com>  and was discussed here:
> >>>>> http://marc.info/?l=linux-serial&m=127416101222281&w=2.
> >>>>> Joonyoung Shim acked my patch and other people on ARM mailing list
> >>>>> acked it. The maintainer, Ben Dooks, still not responding for
> >>>>> a long time. Another maintainer, Kukjin Kim, refused to merge
> >>>>> it without Ben's review.
> >>>>> I would like to ask somebody pick up this bugfix.
> >>>>
> >>>> I belive last time this was brought up I asked about the affect
> >>>> this has on the userspace. The following issues would be helpful
> >>>> or essential to have noted in the header about the effect of this.
> >>>>
> >>>> - Does it change the /dev name of the device? if so I would thinl
> >>>>   carefully about applying it, as it would be a change in the way
> >>>>   that userspace sees the kernel.
> >>>
> >>> It does - now devices are named /dev/s3c2410_serial, and patch changes
> >>> its name to /dev/ttySAC
> >>>
> >>>>
> >>>> - Does it change the kernel output itself? A note on what diffeences
> >>>>   can be seen in things like dmesg would be helpful.
> >>>
> >>> It does. Serial driver reports device names when probing, so there
> >>> will appear ttySACx instead of
> >>> s3c2410_serialx.
> >>>
> >>>>
> >>>> - Are there any other side effects
> >>>>
> >>>> - Why is this a bug? Maybe the previous points will explain what is
> >>>>   going on, but if not, then a reasonably concise description of
> >>>>   what is going on here.
> >>>
> >>> This is bug, because of several points:
> >>>
> >>> 1. Because it contradicts kernel documentation. Please read
> >>> Documentation/arm/Samsung-S3C24XX/Overview.txt line 196.
> >>> This should be enough to apply this patch.
> >>>
> >>> 2. Because s3c2410_serial isn't correct name for serial device node.
> >>> It's name of Samsung serial driver.
> >>>
> >>> 3. Because now almost all userspace systems workaround it by creating
> >>> symlink
> >>> /dev/ttySACx>  /dev/s3c2410_serialx and only then put some getty on
> >>> created symlink, not on original device.
> >>> Systems which don't create this symlink, fail to boot at all, because
> >>> of wrong console name. Good example is Buildroot.
> >>
> >> I had similar issue with buildroot too, because in /etc/securetty it is
> >> defained as ttySAC0
> >>
> >> 4. For console in kernel boot command line you must enter
console=ttySACx.
> >> Why it sould be different in userspace?
> >>
> >> For me it seems taht this bug was not noticed earlier, because most
> >> embedded
> >> systems were using static device nodes and ttySACx was used in these
cases.
> >
> > As long as these are explained, then I'm reasonably happy for this to be
> > applied, as long as there are no other complaints.
> >
> > However, this is a big change, and I think it should await the next
> > merge window.
> 
> I agree that too.
> 

Hi Darius and all,

Maybe you remember this, I applied this in my for-next for 38 this merge
window.
If any opinions, please let me know.

Thanks and Happy New year :)

Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@...sung.com>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.

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