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

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Message-ID: <AANLkTimy=eJKeANFi7VspoB6GrRzW1=36vjbfuNqPRRJ@mail.gmail.com>
Date:	Mon, 27 Sep 2010 11:20:00 +0300
From:	Paulius Zaleckas <paulius.zaleckas@...il.com>
To:	Ben Dooks <ben-linux@...ff.org>
Cc:	Darius Augulis <augulis.darius@...il.com>, kgene.kim@...sung.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

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 also agree that it should be applied to next release.
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