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

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Message-ID: <20121105105602.GC24532@intel.com>
Date:	Mon, 5 Nov 2012 12:56:02 +0200
From:	Mika Westerberg <mika.westerberg@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Bjorn Helgaas <bhelgaas@...gle.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 05, 2012 at 11:31:19AM +0100, Rafael J. Wysocki wrote:
> 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.
> I think adding it would allow us to make acpi_create_platform_device(),
> acpi_spi_add_resources() and acpi_i2c_add_resources() more straightforward (and
> remove some code duplication between the last two routines).

This certainly sounds good to me.

> In addition to that, I'd add an entry containing serial bus information, if
> applicable, for the given struct acpi_device, something like:
> 
> union acpi_resource_serial_bus {
> 	struct acpi_resource_common_serialbus;
> 	struct acpi_resource_spi_serialbus;
> 	struct acpi_resource_i2c_serialbus;
> 	struct acpi_resource_uart_serialbus;
> };
> 
> struct acpi_device {
> 	...
> 	union acpi_resource_serial_bus *serial;
> 	...
> };

It is also possible to have several serial bus connectors on a single
device (although we've seen only one connector per device but it should not
be limited to that).

> Then, things like acpi_spi_add_resources() and acpi_i2c_add_resources() would
> be able to use struct acpi_device objects directly without running any AML.
> That could be done on top of the current series and I'm going to prepare a patch
> for that in the next few days if I find some time between the LCE sessions.

Cool :-) Let me know if you need any help, like testing the patches etc.
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