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Diffstat (limited to 'Documentation/extcon/porting-android-switch-class')
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diff --git a/Documentation/extcon/porting-android-switch-class b/Documentation/extcon/porting-android-switch-class deleted file mode 100644 index 49c81caef84d..000000000000 --- a/Documentation/extcon/porting-android-switch-class +++ /dev/null @@ -1,123 +0,0 @@ - - Staging/Android Switch Class Porting Guide - (linux/drivers/staging/android/switch) - (c) Copyright 2012 Samsung Electronics - -AUTHORS -MyungJoo Ham <myungjoo.ham@samsung.com> - -/***************************************************************** - * CHAPTER 1. * - * PORTING SWITCH CLASS DEVICE DRIVERS * - *****************************************************************/ - -****** STEP 1. Basic Functionality - No extcon extended feature, but switch features only. - -- struct switch_dev (fed to switch_dev_register/unregister) - @name: no change - @dev: no change - @index: drop (not used in switch device driver side anyway) - @state: no change - If you have used @state with magic numbers, keep it - at this step. - @print_name: no change but type change (switch_dev->extcon_dev) - @print_state: no change but type change (switch_dev->extcon_dev) - -- switch_dev_register(sdev, dev) - => extcon_dev_register(edev) - : type change (sdev->edev) - : remove second param('dev'). if edev has parent device, should store - 'dev' to 'edev.dev.parent' before registering extcon device -- switch_dev_unregister(sdev) - => extcon_dev_unregister(edev) - : no change but type change (sdev->edev) -- switch_get_state(sdev) - => extcon_get_state(edev) - : no change but type change (sdev->edev) and (return: int->u32) -- switch_set_state(sdev, state) - => extcon_set_state(edev, state) - : no change but type change (sdev->edev) and (state: int->u32) - -With this changes, the ex-switch extcon class device works as it once -worked as switch class device. However, it will now have additional -interfaces (both ABI and in-kernel API) and different ABI locations. -However, if CONFIG_ANDROID is enabled without CONFIG_ANDROID_SWITCH, -/sys/class/switch/* will be symbolically linked to /sys/class/extcon/ -so that they are still compatible with legacy userspace processes. - -****** STEP 2. Multistate (no more magic numbers in state value) - Extcon's extended features for switch device drivers with - complex features usually required magic numbers in state - value of switch_dev. With extcon, such magic numbers that - support multiple cables are no more required or supported. - - 1. Define cable names at edev->supported_cable. - 2. (Recommended) remove print_state callback. - 3. Use extcon_get_cable_state_(edev, index) or - extcon_get_cable_state(edev, cable_name) instead of - extcon_get_state(edev) if you intend to get a state of a specific - cable. Same for set_state. This way, you can remove the usage of - magic numbers in state value. - 4. Use extcon_update_state() if you are updating specific bits of - the state value. - -Example: a switch device driver w/ magic numbers for two cables. - "0x00": no cables connected. - "0x01": cable 1 connected - "0x02": cable 2 connected - "0x03": cable 1 and 2 connected - 1. edev->supported_cable = {"1", "2", NULL}; - 2. edev->print_state = NULL; - 3. extcon_get_cable_state_(edev, 0) shows cable 1's state. - extcon_get_cable_state(edev, "1") shows cable 1's state. - extcon_set_cable_state_(edev, 1) sets cable 2's state. - extcon_set_cable_state(edev, "2") sets cable 2's state - 4. extcon_update_state(edev, 0x01, 0) sets the least bit's 0. - -****** STEP 3. Notify other device drivers - - You can notify others of the cable attach/detach events with -notifier chains. - - At the side of other device drivers (the extcon device itself -does not need to get notified of its own events), there are two -methods to register notifier_block for cable events: -(a) for a specific cable or (b) for every cable. - - (a) extcon_register_interest(obj, extcon_name, cable_name, nb) - Example: want to get news of "MAX8997_MUIC"'s "USB" cable - - obj = kzalloc(sizeof(struct extcon_specific_cable_nb), - GFP_KERNEL); - nb->notifier_call = the_callback_to_handle_usb; - - extcon_register_intereset(obj, "MAX8997_MUIC", "USB", nb); - - (b) extcon_register_notifier(edev, nb) - Call nb for any changes in edev. - - Please note that in order to properly behave with method (a), -the extcon device driver should support multistate feature (STEP 2). - -****** STEP 4. Inter-cable relation (mutually exclusive) - - You can provide inter-cable mutually exclusiveness information -for an extcon device. When cables A and B are declared to be mutually -exclusive, the two cables cannot be in ATTACHED state simulteneously. - - -/***************************************************************** - * CHAPTER 2. * - * PORTING USERSPACE w/ SWITCH CLASS DEVICE SUPPORT * - *****************************************************************/ - -****** ABI Location - - If "CONFIG_ANDROID" is enabled, /sys/class/switch/* are created -as symbolic links to /sys/class/extcon/*. - - The two files of switch class, name and state, are provided with -extcon, too. When the multistate support (STEP 2 of CHAPTER 1.) is -not enabled or print_state callback is supplied, the output of -state ABI is same with switch class. |