linux-kernel - Re: [PATCH] drivers, char: add U-Boot bootcount driver

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Date:	Tue, 6 Dec 2011 22:50:56 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Heiko Schocher <hs@...x.de>
Cc:	Wolfgang Denk <wd@...x.de>, Vitaly Bordug <vbordug@...mvista.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-watchdog@...r.kernel.org
Subject: Re: [PATCH] drivers, char: add U-Boot bootcount driver

Hi Heiko,

> >> This driver provides read/write access to the U-Boot bootcounter
> >> through PROC FS and/or sysFS file.
> > 
> > Why ProcFS? Why ProcFS and/or SysFS? Which has priority? Why not /dev?
> 
> I drop the ProcFS support for v2.

Don't bother. This approach starts from the wrong side.

> 
> >> The bootcountregister gets configured via DTS.
> >> for example on the enbw_cmc board:
> >>
> >> bootcount@...3060 {
> >>                   compatible = "uboot,bootcount";
> > 
> > No. I assume you are not the vendor of what is at 0x23060, the actual device.
> > Only the device must be encoded in the compatible-entry which then implies the
> > bootcount functionality. Also, keep in mind that your solution should be
> > generic for bootloaders.
> 
> So I should call it compatible = "generic, bootcount" ?

Nope, you should give it the name of the device. Remember that 'compatible' is
no 1:1 replacement for platform_driver-binding. Check
http://devicetree.org/Device_Tree_Usage, especially the sections about the
compatible-property.

bootcount itself is not a device. It is a feature of certain devices. And that
needs to be implemented; possibly generic enough that it can work for register
based, i2c based, and so forth, accesses.

Regards,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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