linux-kernel - Re: [PATCH 2/3] spi / ACPI: add ACPI enumeration support

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Date:	Mon, 5 Nov 2012 09:54:42 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	linux-kernel@...r.kernel.org, lenb@...nel.org,
	rafael.j.wysocki@...el.com, broonie@...nsource.wolfsonmicro.com,
	grant.likely@...retlab.ca, linus.walleij@...aro.org,
	khali@...ux-fr.org, ben-linux@...ff.org, w.sang@...gutronix.de,
	mathias.nyman@...ux.intel.com, linux-acpi@...r.kernel.org
Subject: Re: [PATCH 2/3] spi / ACPI: add ACPI enumeration support

On Mon, Nov 5, 2012 at 3:31 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Saturday, November 03, 2012 09:59:28 PM Rafael J. Wysocki wrote:
>> On Saturday, November 03, 2012 10:13:10 PM Mika Westerberg wrote:
>> > On Sat, Nov 03, 2012 at 01:42:02PM -0600, Bjorn Helgaas wrote:
>> > > On Sat, Nov 3, 2012 at 1:46 AM, Mika Westerberg
>> > > <mika.westerberg@...ux.intel.com> wrote:
>> > > > ACPI 5 introduced SPISerialBus resource that allows us to enumerate and
>> > > > configure the SPI slave devices behind the SPI controller. This patch adds
>> > > > support for this to the SPI core.
> [...]
>> > And if the ACPI core parses the _CRS, how does it pass all the resources to
>> > the drivers?
>>
>> Pretty much the same way the $subject patch does.
>>
>> Instead of parsing the entire subtree below an SPI controller and trying
>> acpi_spi_add_device() for each device node in there, it could call
>> acpi_spi_add_device() whenever it finds a device of type
>> ACPI_RESOURCE_TYPE_SERIAL_BUS/ACPI_RESOURCE_SERIAL_TYPE_SPI.
>> The only problem is how to pass "master" to it.
>>
>> So Bjorn, do you have any idea how we could pass the "master" pointer from the
>> ACPI core to acpi_spi_add_device() in a sensible way?
>>
>> An alternative might be to store the information obtained from _CRS in
>> struct acpi_device objects created by the ACPI core while parsing the
>> namespace.  We do that already for things like _PRW, so we might as well do it
>> for _CRS.  Then, the SPI core could just walk the subtree of the device hierarchy
>> below the SPI controller's acpi_device to extract that information.
>> Maybe that's the way to go?
>
> The general idea is to move the _CRS parsing routine from acpi_platform.c
> to scan.c and make it attach resource objects to struct acpi_device.
>
> I'm thinking about adding a list head to struct acpi_device pointing to a
> list of entries like:
>
> struct resource_list_entry {
>         struct list_head node;
>         struct resource *resources;
>         unsigned int count;
> };
>
> where "resources" is an array of resources (e.g. interrupts) in the given
> entry and count is the size of that array.
>
> That list would contain common resources like ACPI_RESOURCE_TYPE_FIXED_MEMORY32,
> ACPI_RESOURCE_TYPE_IRQ, ACPI_RESOURCE_TYPE_ADDRESS32, ACPI_RESOURCE_TYPE_EXTENDED_IRQ.

This is exactly what PNPACPI already does.  For every Device node in
the namespace, pnpacpi/rsparser.c parses _CRS and builds a list of
struct resources that correspond to it.  If you put this functionality
in acpi/scan.c, should we get rid of PNPACPI?

Bjorn
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