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Date: Wed, 16 Jul 2014 10:21:36 -0700 From: Bryan Wu <cooloney@...il.com> To: Jacek Anaszewski <j.anaszewski@...sung.com> Cc: Linux LED Subsystem <linux-leds@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org>, Kyungmin Park <kyungmin.park@...sung.com>, b.zolnierkie@...sung.com Subject: Re: [PATCH/RFC v4 00/21] LED / flash API integration On Wed, Jul 16, 2014 at 10:19 AM, Bryan Wu <cooloney@...il.com> wrote: > On Fri, Jul 11, 2014 at 7:04 AM, Jacek Anaszewski > <j.anaszewski@...sung.com> wrote: >> This is is the fourth version of the patch series being a follow up >> of the discussion on Media summit 2013-10-23, related to the >> LED / flash API integration (the notes from the discussion were >> enclosed in the message [1], paragraph 5). >> The series is based on linux-next-20140707 >> > > I really apologize that I missed your discussion email in my Gmail > inbox, it was archived some where. Even in this series some of these > patches are archived in different tab. > > I will start to review and help to push this. > In the mean time, could you please provide an git tree for me to pull? It's much easier for me to review in my git. -Bryan > > >> Description of the proposed modifications according to >> the kernel components they are relevant to: >> - LED subsystem modifications >> * added led_flash module which, when enabled in the config, >> registers flash specific sysfs attributes, if the driver >> declares related features: >> - flash_brightness >> - max_flash_brightness >> - indicator_brightness >> - max_indicator_brightness >> - flash_timeout >> - max_flash_timeout >> - flash_strobe >> - external_strobe >> - flash_fault >> and exposes kernel internal API: >> - led_classdev_flash_register >> - led_classdev_flash_unregister >> - led_set_flash_strobe >> - led_get_flash_strobe >> - led_set_flash_brightness >> - led_update_flash_brightness >> - led_set_indicator_brightness >> - led_update_indicator_brightness >> - led_set_flash_timeout >> - led_get_flash_fault >> - led_set_external_strobe >> - led_sysfs_lock >> - led_sysfs_unlock >> * added Flash Manager functionality, available when >> led_flash module is enable in the config; >> if the device tree node of a flash led device contains >> relevant subnodes, it registers following sysfs attributes: >> - strobe_provider >> - strobe_providerN >> - blocking_strobe >> following kernel internal API is exposed by the flash manager: >> - led_flash_manager_register_flash >> - led_flash_manager_unregister_flash >> - led_flash_manager_setup_strobe >> - led_flash_manager_bind_async_mux >> - led_flash_manager_unbind_async_mux >> - Addition of a V4L2 Flash sub-device registration helpers >> * added v4l2-flash.c and v4l2-flash.h files with helper >> functions that facilitate registration/unregistration >> of a subdevice, which wrapps a LED subsystem device and >> exposes V4L2 Flash control interface >> - Addition of a LED Flash Class driver for the flash cell of >> the MAX77693 mfd >> - Addition of a LED Flash Class driver for the AAT1290 current >> regulator for flash leds along with its DT binding for the >> exynos4412-trats2 board, where standalone multiplexer is >> used for modifying strobe signal routing - either from the SoC >> GPIO or from a camera sensor. This arrangment is handled >> by the newly introduced Flash Manager functionality. >> - Update of the max77693.txt DT bindings documentation >> - Update of the common leds DT bindings documentation >> >> ================ >> Changes since v2 >> ================ >> >> - refactored the code so that it is possible to build >> led-core without led-flash module >> - added v4l2-flash ops which slackens dependency from >> the led-flash module >> - implemented led_clamp_align_val function and led_ctrl >> structure which allows to align led control values >> in the manner compatible with V4L2 Flash controls; >> the flash brightness and timeout units have been defined >> as microamperes and microseconds respectively to properly >> support devices which define current and time levels >> as fractions of 1/1000. >> - added support for the flash privacy leds >> - modified LED sysfs locking mechanism - now it locks/unlocks >> the interface on V4L2 Flash sub-device file open/close >> - changed hw_triggered attribute name to external_strobe, >> which maps on the V4L2_FLASH_STROBE_SOURCE_EXTERNAL name >> more intuitively >> - made external_strobe and indicator related sysfs attributes >> created optionally only if related features are declared >> by the led device driver >> - removed from the series patches modifying exynos4-is media >> controller - a proposal for "flash manager" which will take >> care of flash devices registration is due to be submitted >> - removed modifications to the LED class devices documentation, >> it will be covered after the whole functionality is accepted >> >> ================ >> Changes since v3 >> ================ >> >> - added Flash Manager feature >> - added generic LED Flash Class gpio mux driver >> - added sample async mux driver >> - added of helpers for parsing Flash Manager related >> device tree data >> - added V4L2_CID_FLASH_STROBE_PROVIDER control >> - introduced struct led_classdev_flash, which wrapps >> struct led_classdev >> - made all flash ops, except strobe_set, optional; if an op >> is absent the related sysfs attribute isn't created >> - added LED_DEV_CAP* flags >> - modified v4l2-flash helpers to create v4l2_device >> for v4l2_flash subdevices to register in it >> - modified max77693-flash driver and its DT bindings >> to allow for registering either one or two LED Flash >> Class devices, depending on the device tree settings. >> - added new API for setting torch_brightness >> - extended leds common DT binding documentation >> >> Issues: >> >> 1) Who should register V4L2 Flash sub-device? >> >> LED Flash Class devices, after introduction of the Flash Manager, >> are not tightly coupled with any media controller. They are maintained >> by the Flash Manager and made available for dynamic assignment to >> any media system they are connected to through multiplexing devices. >> >> In the proposed rough solution, when support for V4L2 Flash sub-devices >> is enabled, there is a v4l2_device created for them to register in. >> This however implies that V4L2 Flash device will not be available >> in any media controller, which calls its existence into question. >> >> Therefore I'd like to consult possible ways of solving this issue. >> The option I see is implementing a mechanism for moving V4L2 Flash >> sub-devices between media controllers. A V4L2 Flash sub-device >> would initially be assigned to one media system in the relevant >> device tree binding, but it could be dynamically reassigned to >> the other one. However I'm not sure if media controller design >> is prepared for dynamic modifications of its graph and how many >> modifications in the existing drivers this solution would require. >> >> 2) Consequences of locking the Flash Manager during flash strobe >> >> In case a LED Flash Class device depends on muxes involved in >> routing the other LED Flash Class device's strobe signals, >> the Flash Manager must be locked for the time of strobing >> to prevent reconfiguration of the strobe signal routing >> by the other device. >> >> A blocking_strobe sysfs attribute was added to indicate whether >> this is the case for the device. >> >> Nonetheless, this modifies behaviour of led_set_external_strobe >> API, which also must block the caller for the time of strobing >> to protect the strobe signal routing while the external strobe >> signal provider asserts the flash_en pin. >> >> Use case for user space application would be following in this case: >> - spawn a new thread in which external strobe is activated >> - in the parent thread instruct the external strobe provider >> to strobe the flash >> >> As an improvement there could be an op added for notifying >> the application that the strobe signal routing has been >> set up. It would have to be called from the function >> led_flash_manager_setup_strobe after led_flash_manager_set_external_strobe >> returns. >> >> The blocking_strobe attribute would have to be also >> mapped to a new V4L2 Flash control. Unfortunately it poses >> a problem for the existing users of the V4L2 Flash API >> which are not aware that setting V4L2_CID_FLASH_STROBE_SOURCE >> may be blocking. >> >> As a solution led_set_external_strobe API could be extended >> by a parameter telling whether the caller is prepared for >> the blocking call. led_flash_manager_setup_strobe should >> be extended accordingly then. >> In V4L2 "V4L2_FLASH_STROBE_SOURCE_EXTERNAL_BLOCKING" menu item >> could be added to handle this. >> With existing V4L2_FLASH_STROBE_SOURCE_EXTERNAL the flash manager >> wouldn't protect muxes against reconfiguration. >> >> TODO: >> - switch to using V4L2 array controls >> - add s_power op to the LED Flash Class >> >> >> I will be off-line for three weeks from now on and will respond >> to any questions after getting back. >> >> >> Thanks, >> Jacek Anaszewski >> >> Jacek Anaszewski (21): >> leds: make brightness type consistent across whole subsystem >> leds: implement sysfs interface locking mechanism >> leds: Improve and export led_update_brightness >> leds: Reorder include directives >> leds: avoid using deprecated DEVICE_ATTR macro >> leds: add API for setting torch brightness >> of: add of_node_ncmp wrapper >> leds: Add sysfs and kernel internal API for flash LEDs >> Documentation: leds: Add description of LED Flash Class extension >> Documentation: leds: add exemplary asynchronous mux driver >> DT: leds: Add flash led devices related properties >> DT: Add documentation for LED Class Flash Manger >> v4l2-device: add v4l2_device_register_subdev_node API >> v4l2-ctrls: add control for flash strobe signal providers >> media: Add registration helpers for V4L2 flash >> leds: Add support for max77693 mfd flash cell >> DT: Add documentation for the mfd Maxim max77693 >> leds: Add driver for AAT1290 current regulator >> of: Add Skyworks Solutions, Inc. vendor prefix >> DT: Add documentation for the Skyworks AAT1290 >> ARM: dts: add aat1290 current regulator device node >> >> Documentation/DocBook/media/v4l/controls.xml | 11 + >> Documentation/devicetree/bindings/leds/common.txt | 16 + >> .../devicetree/bindings/leds/leds-aat1290.txt | 17 + >> .../bindings/leds/leds-flash-manager.txt | 165 +++ >> Documentation/devicetree/bindings/mfd/max77693.txt | 62 ++ >> .../devicetree/bindings/vendor-prefixes.txt | 1 + >> Documentation/leds/leds-async-mux.c | 65 ++ >> Documentation/leds/leds-class-flash.txt | 126 +++ >> arch/arm/boot/dts/exynos4412-trats2.dts | 24 + >> drivers/leds/Kconfig | 28 + >> drivers/leds/Makefile | 7 + >> drivers/leds/led-class-flash.c | 715 +++++++++++++ >> drivers/leds/led-class.c | 58 +- >> drivers/leds/led-core.c | 51 +- >> drivers/leds/led-flash-gpio-mux.c | 102 ++ >> drivers/leds/led-flash-manager.c | 698 +++++++++++++ >> drivers/leds/led-triggers.c | 16 +- >> drivers/leds/leds-aat1290.c | 455 +++++++++ >> drivers/leds/leds-max77693.c | 1070 ++++++++++++++++++++ >> drivers/leds/of_led_flash_manager.c | 155 +++ >> drivers/media/v4l2-core/Kconfig | 11 + >> drivers/media/v4l2-core/Makefile | 2 + >> drivers/media/v4l2-core/v4l2-ctrls.c | 2 + >> drivers/media/v4l2-core/v4l2-device.c | 63 +- >> drivers/media/v4l2-core/v4l2-flash.c | 580 +++++++++++ >> drivers/mfd/max77693.c | 5 +- >> include/linux/led-class-flash.h | 290 ++++++ >> include/linux/led-flash-gpio-mux.h | 68 ++ >> include/linux/led-flash-manager.h | 121 +++ >> include/linux/leds.h | 73 +- >> include/linux/mfd/max77693.h | 40 + >> include/linux/of.h | 1 + >> include/linux/of_led_flash_manager.h | 80 ++ >> include/media/v4l2-device.h | 7 + >> include/media/v4l2-flash.h | 137 +++ >> include/uapi/linux/v4l2-controls.h | 2 + >> 36 files changed, 5272 insertions(+), 52 deletions(-) >> create mode 100644 Documentation/devicetree/bindings/leds/leds-aat1290.txt >> create mode 100644 Documentation/devicetree/bindings/leds/leds-flash-manager.txt >> create mode 100644 Documentation/leds/leds-async-mux.c >> create mode 100644 Documentation/leds/leds-class-flash.txt >> create mode 100644 drivers/leds/led-class-flash.c >> create mode 100644 drivers/leds/led-flash-gpio-mux.c >> create mode 100644 drivers/leds/led-flash-manager.c >> create mode 100644 drivers/leds/leds-aat1290.c >> create mode 100644 drivers/leds/leds-max77693.c >> create mode 100644 drivers/leds/of_led_flash_manager.c >> create mode 100644 drivers/media/v4l2-core/v4l2-flash.c >> create mode 100644 include/linux/led-class-flash.h >> create mode 100644 include/linux/led-flash-gpio-mux.h >> create mode 100644 include/linux/led-flash-manager.h >> create mode 100644 include/linux/of_led_flash_manager.h >> create mode 100644 include/media/v4l2-flash.h >> >> -- >> 1.7.9.5 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-media" in >> the body of a message to majordomo@...r.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" 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