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Diffstat (limited to 'Documentation/acpi/enumeration.txt')
| -rw-r--r-- | Documentation/acpi/enumeration.txt | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt index e182be5e3c83..b60d2ab69497 100644 --- a/Documentation/acpi/enumeration.txt +++ b/Documentation/acpi/enumeration.txt @@ -312,3 +312,30 @@ a code like this: There are also devm_* versions of these functions which release the descriptors once the device is released. + +MFD devices +~~~~~~~~~~~ +The MFD devices register their children as platform devices. For the child +devices there needs to be an ACPI handle that they can use to reference +parts of the ACPI namespace that relate to them. In the Linux MFD subsystem +we provide two ways: + + o The children share the parent ACPI handle. + o The MFD cell can specify the ACPI id of the device. + +For the first case, the MFD drivers do not need to do anything. The +resulting child platform device will have its ACPI_COMPANION() set to point +to the parent device. + +If the ACPI namespace has a device that we can match using an ACPI id, +the id should be set like: + + static struct mfd_cell my_subdevice_cell = { + .name = "my_subdevice", + /* set the resources relative to the parent */ + .acpi_pnpid = "XYZ0001", + }; + +The ACPI id "XYZ0001" is then used to lookup an ACPI device directly under +the MFD device and if found, that ACPI companion device is bound to the +resulting child platform device. |