Re: [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes

From: Lee Jones <lee.jones@linaro.org>
To: Frank Rowand <frowand.list@gmail.com>
Cc: andy.shevchenko@gmail.com, michael@walle.cc, robh+dt@kernel.org,
	broonie@kernel.org, devicetree@vger.kernel.org,
	linus.walleij@linaro.org, linux@roeck-us.net,
	andriy.shevchenko@linux.intel.com, robin.murphy@arm.com,
	gregkh@linuxfoundation.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes
Date: Wed, 24 Jun 2020 07:41:45 +0100	[thread overview]
Message-ID: <20200624064145.GC954398@dell> (raw)
In-Reply-To: <30f03734-61fd-1b6b-bf11-21b6423a7c50@gmail.com>

On Tue, 23 Jun 2020, Frank Rowand wrote:

> On 2020-06-11 14:10, Lee Jones wrote:
> > Currently, when a child platform device (sometimes referred to as a
> > sub-device) is registered via the Multi-Functional Device (MFD) API,
> > the framework attempts to match the newly registered platform device
> > with its associated Device Tree (OF) node.  Until now, the device has
> > been allocated the first node found with an identical OF compatible
> > string.  Unfortunately, if there are, say for example '3' devices
> > which are to be handled by the same driver and therefore have the same
> > compatible string, each of them will be allocated a pointer to the
> > *first* node.
> 
> As you mentioned elsewhere in this thread, this series "fixes" the
> problem related to the "stericsson,ab8500-pwm" compatible.
> 
> I know, I said I would drop discussion of that compatible, but bear
> with me for a second.  :-)
> 
> The "problem" is that the devices for multiple mfd child nodes with
> the same compatible value of "stericsson,ab8500-pwm" will all have
> a pointer to the first child node.  At the moment the same child
> of_node being used by more than one device does not cause any
> incorrect behavior.
> 
> Just in case the driver for "stericsson,ab8500-pwm" is modified
> in a way that the child of_node needs to be distinct for each
> device, and that changes gets back ported, it would be useful
> to have Fixes: tags for this patch series.
> 
> So, at your discretion (and I'll let you worry about the correct
> Fixes: tag format), this series fixes:
> 
> bad76991d7847b7877ae797cc79745d82ffd9120 mfd: Register ab8500 devices using the newly DT:ed MFD API

This patch isn't actually broken.

The issue is the DTB, which [0] addresses.

[0]
https://lkml.kernel.org/lkml/20200622083432.1491715-1-lee.jones@linaro.org/

> c94bb233a9fee3314dc5d9c7de9fa702e91283f2 mfd: Make MFD core code Device Tree and IRQ domain aware

It sounds reasonable to list this one, thanks.

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog