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    SubjectRe: [PATCH 3/3] ACPI: Evaluate _CRS while creating device node objects
    On Mon, Nov 12, 2012 at 01:02:11PM +0100, Rafael J. Wysocki wrote:
    > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    >
    > Currently, whoever wants to use ACPI device resources has to call
    > acpi_walk_resources() to browse the buffer returned by the _CRS
    > method for the given device and create filters passed to that
    > routine to apply to the individual resource items. This generally
    > is cumbersome, time-consuming and inefficient. Moreover, it may
    > be problematic if resource conflicts need to be resolved, because
    > the different users of _CRS will need to do that in a consistent
    > way.
    >
    > For this reason, add code to the ACPI core to execute _CRS once,
    > when the struct acpi_device object is created for a given device
    > node, and attach a list of ACPI resources returned by _CRS to that
    > object for future processing.
    >
    > Convert the ACPI code that creates platform device objects to using
    > the new resources list instead of executing acpi_walk_resources() by
    > itself, which makes it much more straightforward and easier to
    > follow.
    >
    > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    > ---
    > drivers/acpi/acpi_platform.c | 90 ++++++++++++-------------------------------
    > drivers/acpi/resource.c | 12 +++++
    > drivers/acpi/scan.c | 56 ++++++++++++++++++++++++++
    > include/acpi/acpi_bus.h | 6 ++
    > include/linux/acpi.h | 1
    > 5 files changed, 102 insertions(+), 63 deletions(-)
    >
    > Index: linux/include/acpi/acpi_bus.h
    > ===================================================================
    > --- linux.orig/include/acpi/acpi_bus.h
    > +++ linux/include/acpi/acpi_bus.h
    > @@ -259,6 +259,11 @@ struct acpi_device_physical_node {
    > struct device *dev;
    > };
    >
    > +struct acpi_resource_list_entry {
    > + struct list_head node;
    > + struct acpi_resource resource;
    > +};
    > +
    > /* set maximum of physical nodes to 32 for expansibility */
    > #define ACPI_MAX_PHYSICAL_NODE 32
    >
    > @@ -268,6 +273,7 @@ struct acpi_device {
    > acpi_handle handle; /* no handle for fixed hardware */
    > struct acpi_device *parent;
    > struct list_head children;
    > + struct list_head resources; /* Device resources. */
    > struct list_head node;
    > struct list_head wakeup_list;
    > struct acpi_device_status status;
    > Index: linux/drivers/acpi/scan.c
    > ===================================================================
    > --- linux.orig/drivers/acpi/scan.c
    > +++ linux/drivers/acpi/scan.c
    > @@ -382,6 +382,52 @@ static void acpi_device_remove_files(str
    > ACPI Bus operations
    > -------------------------------------------------------------------------- */
    >
    > +static void acpi_bus_drop_resources(struct acpi_device *adev)
    > +{
    > + struct acpi_resource_list_entry *entry, *s;
    > +
    > + list_for_each_entry_safe(entry, s, &adev->resources, node) {
    > + list_del(&entry->node);
    > + kfree(entry);
    > + }
    > +}
    > +
    > +static acpi_status acpi_bus_add_resource(struct acpi_resource *res,
    > + void *context)
    > +{
    > + struct list_head *list = context;
    > + struct acpi_resource_list_entry *entry;
    > +
    > + entry = kzalloc(sizeof(*entry), GFP_KERNEL);
    > + if (!entry)
    > + return AE_NO_MEMORY;
    > +
    > + entry->resource = *res;

    This does not work well with all resource types - specifically those that
    contain pointers, like acpi_resource_gpio and acpi_resource_source.

    The memory for the resources gets freed once acpi_walk_resources() is done.

    > + INIT_LIST_HEAD(&entry->node);
    > + list_add_tail(&entry->node, list);
    > + return AE_OK;
    > +}


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