Add short documentation providing the driver usage details. Signed-off-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx> --- Documentation/video4linux/fimc.txt | 178 ++++++++++++++++++++++++++++++++++++ 1 files changed, 178 insertions(+), 0 deletions(-) create mode 100644 Documentation/video4linux/fimc.txt diff --git a/Documentation/video4linux/fimc.txt b/Documentation/video4linux/fimc.txt new file mode 100644 index 0000000..81d6d2c --- /dev/null +++ b/Documentation/video4linux/fimc.txt @@ -0,0 +1,178 @@ +Samsung S5P/EXYNOS4 FIMC driver + +Copyright (C) 2011 Samsung Electronics Co., Ltd. +------------------------------------------------------------------------------ + +This text describes the design of v4l2 driver for FIMC (Fully Interfactive +Mobile Camera) devices present on Samsung SoC Application Processor series. +FIMC IP is an integrated camera host interface, color space converter, image +scaler and rotator. It's also capable of capturing data from LCD controller +(FIMD) through the SoC internal writeback data path. On the SoCs this driver +supports there are multiple instances of the IP (up to 4), having slightly +different capabilities, like pixel alignment constraints, rotator availability, +LCD writeback support, etc. +The driver is located at drivers/media/video/s5p-fimc directory. + + +1. Supported SoCs +================= + +S5PC100 (mem-to-mem only), S5PV210, EXYNOS4210 + +2. Supported features +===================== + + - camera parallel interface capture (ITU-R.BT601/565); + - camera serial interface capture (MIPI-CSI2); + - memory-to-memory processing (color space conversion, scaling, mirror; + and rotation); + - dynamic pipeline re-configuration at runtime (re-attachment of any FIMC + instance to any parallel video input or any MIPI-CSI front-end); + - runtime PM and system wide suspend/resume + +Not currently supported: + - LCD writeback input + - RGB alpha (exynos4 only) + - per frame clock gating (mem-to-mem) + +3. Files partitioning +===================== + +- media device driver + drivers/media/video/s5p-fimc/fimc-mdevice.[ch] + + - camera capture video device driver + drivers/media/video/s5p-fimc/fimc-capture.c + + - MIPI-CSI2 receiver subdev + drivers/media/video/s5p-fimc/mipi-csis.[ch] + + - video post-processor (mem-to-mem) + drivers/media/video/s5p-fimc/fimc-core.c + + - common files + drivers/media/video/s5p-fimc/fimc-core.h + drivers/media/video/s5p-fimc/fimc-reg.h + drivers/media/video/s5p-fimc/regs-fimc.h + +4. User space interfaces +======================== + +4.1. Media device interface + +The driver supports Media Controller API as defined at +http://http://linuxtv.org/downloads/v4l-dvb-apis/media_common.html +The media device driver name is "SAMSUNG S5P FIMC". + +The purpose of this interface is to allow changing the assignment of FIMC instance +to the SoC peripheral camera input at runtime and optionally to control internal +connections of the MIPI-CSIS device(s) to the FIMC entities. + +The media device interface allows to configure the SoC for capturing image data +from the sensor through more than one FIMC instance (e.g. for simultaneous +viewfinder and capture data stream). +Reconfiguration is done by enabling/disabling the media links created by +the driver during initialization. The internal device topology can be easily +discovered through media entity and links enumeration. + +4.2. Memory-to-memory video node + +V4L2 memory-to-memory interface at /dev/video? device node. This is standalone +video device, it has no media pads. However please note the mem-to-mem and +capture video node operation on same FIMC instance is not allowed. The driver +detects such cases but the applications should prevent them to avoid an +undefined behaviour. + +4.3. Capture video node + +The driver supports V4L2 Video Capture Interface as defined at: +http://linuxtv.org/downloads/v4l-dvb-apis/devices.html + +At the capture and mem-to-mem video nodes only the multi-planar API is supported. +For more details see: http://linuxtv.org/downloads/v4l-dvb-apis/planar-apis.html + +4.4. Camera capture subdevs + +Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device +node is also created per each available and enabled at the platform level +MIPI-CSI receiver device (currently up to two). + +4.5. sysfs + +In order to enable more precise camera pipeline control through the sub-device +API the driver creates a sysfs entry associated with "s5p-fimc-md" platform +device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode. + +In typical use case there could be a following capture pipeline configuration: +sensor subdev -> mipi-csi subdev -> fimc subdev -> video node + +When we configure these devices through sub-device API at user space, +the configuration flow must be from left to right, and the video node +is configured as last one. +When we don't use sub-device user space API the whole configuration of all +devices belonging to the pipeline is done at video node. +The sysfs entry allows to instruct the capture video node driver not to +configure the sub-devices (format, crop), to avoid resetting the subdevs' +configuration when the last configuration steps at the video node are performed. + +For full sub-device control support (subdevs configured at user space +before starting streaming): +# echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode + +For V4L2 video node control only (subdevs configured internally by the host +driver): +# echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode +This is the default option. + +5. Device mapping to video and subdev device nodes +================================================== + +Each FIMC instance creates two video device nodes, for camera capture and +mem-to-mem, and a subdev node for more precise control of the FIMC capture +subsystem. In addition separate v4l2 sub-device node is created per each +MIPI-CSIS device. + +How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which +device? + +You can either grep through the kernel log to find relevant information, i.e. +# dmesg | grep -i fimc +(note that udev, if present, might still have rearranged the video nodes), + +or retrieve the information from /dev/media? with help of the media-ctl tool: +# media-ctl -p + +6. Platform support +=================== + +The machine code (plat-s5p and arch/arm/mach-*) must select following options + +CONFIG_S5P_DEV_FIMC0 (mandatory) +CONFIG_S5P_DEV_FIMC1 \ +CONFIG_S5P_DEV_FIMC2 | optional +CONFIG_S5P_DEV_FIMC3 / +CONFIG_S5P_SETUP_MIPIPHY \ +CONFIG_S5P_DEV_CSIS0 | optional for MIPI-CSI interface +CONFIG_S5P_DEV_CSIS1 / + +Except that, relevant s5p_device_fimc? should be registered in the machine code +in addition to a "s5p-fimc-md" platform device to which the media device driver +is bound. The "s5p-fimc-md" device instance is required even if only mem-to-mem +operation is used. + +The description of sensor(s) attached to FIMC/MIPI-CSIS camera inputs should be +passed as the "s5p-fimc-md" device platform_data. The platform data structure +is defined in file include/media/s5p_fimc.h. + +7. Build +======== + +This driver depends on following config options: +PLAT_S5P, +PM_RUNTIME, +I2C, +VIDEO_V4L2_SUBDEV_API, + +If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m) +two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and +optional s5p-csis.ko (MIPI-CSI receiver subdev). -- 1.7.8.3 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
