linux-kernel - Re: [PATCH 3/3] gpiolib: use chip->names for symlinks, always use gpioN for device names

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Date:	Thu, 10 Dec 2009 20:38:49 -0800
From:	Greg KH <gregkh@...e.de>
To:	David Brownell <david-b@...bell.net>
Cc:	Jani Nikula <ext-jani.1.nikula@...ia.com>,
	dbrownell@...rs.sourceforge.net, linux-kernel@...r.kernel.org,
	dsilvers@...tec.co.uk, ben@...tec.co.uk,
	Artem.Bityutskiy@...ia.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 3/3] gpiolib: use chip->names for symlinks, always use
	gpioN for device names

On Thu, Dec 10, 2009 at 08:13:58PM -0800, David Brownell wrote:
> On Thursday 10 December 2009, Greg KH wrote:
> > 
> > > IMO a "good" solution in this space needs to accept that
> > > those names are not going to be globally unique ... but
> > > that they'll be unique within some context, of necessity.
> > > 
> > > If Greg doesn't want to see those names under classes,
> > > so be it ... but where should they then appear?
> > 
> > As a sysfs file within the device directory called 'name'? ?Then just
> > grep through the tree to find the right device, that also handles
> > duplicates just fine, right?
> 
> I want a concrete example.  Those chip->names things don't
> seem helpful to me though...
> 
> If for example I were building a JTAG adapter on Linux, it
> might consist of a spidev node (chardev) plus a handful of
> GPIOs.  So "the device directory" would be the sysfs home
> of that spidev node (or some variant)?  And inside that
> directory would be files named after various signals that
> are used as GPIOs ... maybe SRST, TRST, and DETECT to start
> with?  Holding some cookie that gets mapped to those GPIO's
> sysfs entries?

Um, I really don't know, as I don't know the GPIO subsystem, nor why you
all have this problem in the first place :)

I also find it funny that you think changing the kernel is easier than
userspace, that's a strange situation.

Anyway, I assumed that you already have a struct device for the GPIO
devices, right?  Put it in there was what I was thinking, but as I don't
understand your current layout, I really don't know.

> I confess I'd still think a symlink from that directory
> to the real GPIO would be easier to work with...

No, don't do that, no symlinks from a class please.

thanks,

greg k-h
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