[PATCH] mtd: Add partition device node to mtd partition devices

[Uwe Kleine-König]

Hello Boris,

On Thu, Feb 09, 2017 at 08:59:22PM +0100, Boris Brezillon wrote:
> On Thu, 9 Feb 2017 20:39:40 +0100
> Uwe Kleine-König <u.kleine-koenig at pengutronix.de> wrote:
> 
> > On Thu, Feb 09, 2017 at 04:34:58PM +0100, Boris Brezillon wrote:
> > > +Moritz
> > > 
> > > On Thu,  9 Feb 2017 11:50:24 +0100
> > > Uwe Kleine-König <u.kleine-koenig at pengutronix.de> wrote:
> > >   
> > > > From: Sascha Hauer <s.hauer at pengutronix.de>
> > > > 
> > > > The user visible change here is that mtd partitions get an of_node link
> > > > in sysfs.  
> > > 
> > > The same patch has already been posted last year [1].
> > > Brian, can we take one of these?
> > > 
> > > [1]https://patchwork.ozlabs.org/patch/625978/  
> > 
> > Moritz' patch is more lame, it even updates the documentation (ok, one
> > point for Moriz :-) Other than that the only difference is "node" vs.
> > "of_node" (half a point for Sascha) and the position of the assignment
> > in mtdpart.c has a different position (another half point for Sascha).
> > 
> > If that would be liked to be seen I can volunteer to create a patch
> > picking the best from both sources.
> 
> Sure, you can also add my ack (which I already put on Moritz patch).
> BTW, is the of_node link in sysfs the only motivation for this change?
> I know Moritz had bigger plans (nvmem blocks on top of MTD devices), and
> I also considered advanced stuff (like per-partition ECC config) which
> required having a valid ->of_node on slave MTD devices.

The motivation for Sascha to create this patch and now me to mainline
it, is that we specify some non-volatile state space in dts (to store
for example hardware revision, serial number and mac addresses). See
http://barebox.org/doc/latest/devicetree/bindings/barebox/barebox,state.html
for some details.

For the userspace part we read the dtb, something like

	state {
		compatible = "barebox,state";
		backend = &mtdstatepartition;
		...
	}

, and with the symlink introduced by the patch under discussion it gets
much simpler to find the device file (in /dev) that contains our state
data.

Best regards
Uwe

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