linux-kernel - Re: [RFC 1/8] serial:st-asc: Add ST ASC driver.

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Date:	Wed, 8 May 2013 09:15:27 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Srinivas KANDAGATLA <srinivas.kandagatla@...com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Will Deacon <will.deacon@....com>, jslaby@...e.cz,
	Russell King <linux@....linux.org.uk>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Nicolas Pitre <nico@...aro.org>, linux-doc@...r.kernel.org,
	Stephen Gallimore <stephen.gallimore@...com>,
	linux-serial@...r.kernel.org, Jason Cooper <jason@...edaemon.net>,
	devicetree-discuss@...ts.ozlabs.org,
	Rob Herring <rob.herring@...xeda.com>,
	Stuart Menefy <stuart.menefy@...com>,
	Stephen Warren <swarren@...dia.com>,
	Dong Aisheng <dong.aisheng@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/8] serial:st-asc: Add ST ASC driver.

On Thu, May 09, 2013 at 12:03:05AM +0800, Jean-Christophe PLAGNIOL-VILLARD wrote:
> 
> On May 8, 2013, at 11:53 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> 
> > On Wed, May 08, 2013 at 05:40:57PM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> >> On 08:34 Wed 08 May     , Greg KH wrote:
> >>> On Wed, May 08, 2013 at 04:34:43PM +0200, Arnd Bergmann wrote:
> >>>>> +#define ASC_MAJOR		204
> >>>>> +#define ASC_MINOR_START		40
> >>>> 
> >>>> I don't know what the current policy is on allocating major/minor numbers,
> >>>> but I'm sure you cannot just reuse one that is already used.
> >>> 
> >>> I agree, why are you trying to create a new tty device name?  Can't you
> >>> use the existing ttyS name and minor number as you will not have any
> >>> other type of serial device on this system?
> >> 
> >> Greg on ST STB for more than 10 years we use ttyASC I'll prefer ttySx
> > 
> > For 10+ years you have had an out-of-tree serial driver?
> yes ST have it out of tree for very long time even I puts them to come mainline

Crazy...

> >  What
> > major/minor numbers did you use for it?
> 
> http://git.stlinux.com/?p=havana/com.st.havana.kernel.git;a=blob;f=drivers/serial/stm-asc.h;h=79e003ffeb21df55a6af94774fc9c4b3d8de18e9;hb=HEAD
> 
>   52 #define ASC_MAJOR               204
>   53 #define ASC_MINOR_START         40
> 
> same as in this patch

Ok, but just because you have been using an out-of-tree name, and
non-reserved major/minor, doesn't mean we have to accept it.  As you are
probably using a tool like udev/devtmpfs on your systems, the
major/minor number shouldn't matter, only the name.

And I'd argue that we should change the name as well.

> >> on the DTB SoC you have one one IP present the st,asc
> > 
> > I don't understand, what do you mean by this?
> > 
> > confused,
> 
> just mention there is not hardware reason to not use the generic ttySx
> in place of ttyAS as we have only one IP that handle serial on this
> family of SoC
> 
> personally I'll switch to ttySx

Great, then you can use the same major/minor range as well, so there's
no more objection from me about this :)

thanks,

greg k-h
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