linux-kernel - Re: [RFC PATCH 06/10] spi: add support for ACPI reconfigure notifications

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Date:	Fri, 1 Apr 2016 21:26:38 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Mark Brown <broonie@...nel.org>
Cc:	Octavian Purdila <octavian.purdila@...el.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Wolfram Sang <wsa@...-dreams.de>,
	Joel Becker <jlbec@...lplan.org>,
	Christoph Hellwig <hch@....de>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	linux-efi@...r.kernel.org, linux-i2c <linux-i2c@...r.kernel.org>,
	linux-spi@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
	Irina Tirdea <irina.tirdea@...el.com>
Subject: Re: [RFC PATCH 06/10] spi: add support for ACPI reconfigure notifications

On Fri, Apr 1, 2016 at 4:08 PM, Mark Brown <broonie@...nel.org> wrote:
> On Fri, Apr 01, 2016 at 01:54:28PM +0300, Octavian Purdila wrote:
>
>> I probably don't fully understand your question, but I don't see a way
>> of how we can create a new SPI device from generic ACPI code. For
>> example, in acpi_spi_add_device() we need the spi_master node so that
>> we can allocate the spi device.
>
> Right, but the same applies to initial enumeration so we also have to
> manually instantiate ACPI devices on startup.  Why do we need to do
> that?
>
>> The handling is identical because we don't have yet have a way to
>> identify what where the new nodes added when a new ACPI table /
>> overlay has been loaded, so we have to rescan the ACPI namespace under
>> each controller.
>
> That's not the point.  The point is that since the handling is identical
> why are we handling it through exactly the same code?

I think that during the initial enumeration the controller driver's
probe walks the children and creates device objects for them.  When a
table is loaded later, the controller driver has been probed already
and there needs to be a way to trigger a walk over the (new) children
from it.

Or a hook somewhere around acpi_platform_notify() is needed.