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diff --git a/Documentation/userspace-api/media/drivers/omap3isp-uapi.rst b/Documentation/userspace-api/media/drivers/omap3isp-uapi.rst new file mode 100644 index 0000000000..5f966a874a --- /dev/null +++ b/Documentation/userspace-api/media/drivers/omap3isp-uapi.rst @@ -0,0 +1,208 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. include:: <isonum.txt> + +OMAP 3 Image Signal Processor (ISP) driver +========================================== + +Copyright |copy| 2010 Nokia Corporation + +Copyright |copy| 2009 Texas Instruments, Inc. + +Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>, +Sakari Ailus <sakari.ailus@iki.fi>, David Cohen <dacohen@gmail.com> + + +Events +------ + +The OMAP 3 ISP driver does support the V4L2 event interface on CCDC and +statistics (AEWB, AF and histogram) subdevs. + +The CCDC subdev produces V4L2_EVENT_FRAME_SYNC type event on HS_VS +interrupt which is used to signal frame start. Earlier version of this +driver used V4L2_EVENT_OMAP3ISP_HS_VS for this purpose. The event is +triggered exactly when the reception of the first line of the frame starts +in the CCDC module. The event can be subscribed on the CCDC subdev. + +(When using parallel interface one must pay account to correct configuration +of the VS signal polarity. This is automatically correct when using the serial +receivers.) + +Each of the statistics subdevs is able to produce events. An event is +generated whenever a statistics buffer can be dequeued by a user space +application using the VIDIOC_OMAP3ISP_STAT_REQ IOCTL. The events available +are: + +- V4L2_EVENT_OMAP3ISP_AEWB +- V4L2_EVENT_OMAP3ISP_AF +- V4L2_EVENT_OMAP3ISP_HIST + +The type of the event data is struct omap3isp_stat_event_status for these +ioctls. If there is an error calculating the statistics, there will be an +event as usual, but no related statistics buffer. In this case +omap3isp_stat_event_status.buf_err is set to non-zero. + + +Private IOCTLs +-------------- + +The OMAP 3 ISP driver supports standard V4L2 IOCTLs and controls where +possible and practical. Much of the functions provided by the ISP, however, +does not fall under the standard IOCTLs --- gamma tables and configuration of +statistics collection are examples of such. + +In general, there is a private ioctl for configuring each of the blocks +containing hardware-dependent functions. + +The following private IOCTLs are supported: + +- VIDIOC_OMAP3ISP_CCDC_CFG +- VIDIOC_OMAP3ISP_PRV_CFG +- VIDIOC_OMAP3ISP_AEWB_CFG +- VIDIOC_OMAP3ISP_HIST_CFG +- VIDIOC_OMAP3ISP_AF_CFG +- VIDIOC_OMAP3ISP_STAT_REQ +- VIDIOC_OMAP3ISP_STAT_EN + +The parameter structures used by these ioctls are described in +include/linux/omap3isp.h. The detailed functions of the ISP itself related to +a given ISP block is described in the Technical Reference Manuals (TRMs) --- +see the end of the document for those. + +While it is possible to use the ISP driver without any use of these private +IOCTLs it is not possible to obtain optimal image quality this way. The AEWB, +AF and histogram modules cannot be used without configuring them using the +appropriate private IOCTLs. + + +CCDC and preview block IOCTLs +----------------------------- + +The VIDIOC_OMAP3ISP_CCDC_CFG and VIDIOC_OMAP3ISP_PRV_CFG IOCTLs are used to +configure, enable and disable functions in the CCDC and preview blocks, +respectively. Both IOCTLs control several functions in the blocks they +control. VIDIOC_OMAP3ISP_CCDC_CFG IOCTL accepts a pointer to struct +omap3isp_ccdc_update_config as its argument. Similarly VIDIOC_OMAP3ISP_PRV_CFG +accepts a pointer to struct omap3isp_prev_update_config. The definition of +both structures is available in [#]_. + +The update field in the structures tells whether to update the configuration +for the specific function and the flag tells whether to enable or disable the +function. + +The update and flag bit masks accept the following values. Each separate +functions in the CCDC and preview blocks is associated with a flag (either +disable or enable; part of the flag field in the structure) and a pointer to +configuration data for the function. + +Valid values for the update and flag fields are listed here for +VIDIOC_OMAP3ISP_CCDC_CFG. Values may be or'ed to configure more than one +function in the same IOCTL call. + +- OMAP3ISP_CCDC_ALAW +- OMAP3ISP_CCDC_LPF +- OMAP3ISP_CCDC_BLCLAMP +- OMAP3ISP_CCDC_BCOMP +- OMAP3ISP_CCDC_FPC +- OMAP3ISP_CCDC_CULL +- OMAP3ISP_CCDC_CONFIG_LSC +- OMAP3ISP_CCDC_TBL_LSC + +The corresponding values for the VIDIOC_OMAP3ISP_PRV_CFG are here: + +- OMAP3ISP_PREV_LUMAENH +- OMAP3ISP_PREV_INVALAW +- OMAP3ISP_PREV_HRZ_MED +- OMAP3ISP_PREV_CFA +- OMAP3ISP_PREV_CHROMA_SUPP +- OMAP3ISP_PREV_WB +- OMAP3ISP_PREV_BLKADJ +- OMAP3ISP_PREV_RGB2RGB +- OMAP3ISP_PREV_COLOR_CONV +- OMAP3ISP_PREV_YC_LIMIT +- OMAP3ISP_PREV_DEFECT_COR +- OMAP3ISP_PREV_GAMMABYPASS +- OMAP3ISP_PREV_DRK_FRM_CAPTURE +- OMAP3ISP_PREV_DRK_FRM_SUBTRACT +- OMAP3ISP_PREV_LENS_SHADING +- OMAP3ISP_PREV_NF +- OMAP3ISP_PREV_GAMMA + +The associated configuration pointer for the function may not be NULL when +enabling the function. When disabling a function the configuration pointer is +ignored. + + +Statistic blocks IOCTLs +----------------------- + +The statistics subdevs do offer more dynamic configuration options than the +other subdevs. They can be enabled, disable and reconfigured when the pipeline +is in streaming state. + +The statistics blocks always get the input image data from the CCDC (as the +histogram memory read isn't implemented). The statistics are dequeueable by +the user from the statistics subdev nodes using private IOCTLs. + +The private IOCTLs offered by the AEWB, AF and histogram subdevs are heavily +reflected by the register level interface offered by the ISP hardware. There +are aspects that are purely related to the driver implementation and these are +discussed next. + +VIDIOC_OMAP3ISP_STAT_EN +----------------------- + +This private IOCTL enables/disables a statistic module. If this request is +done before streaming, it will take effect as soon as the pipeline starts to +stream. If the pipeline is already streaming, it will take effect as soon as +the CCDC becomes idle. + +VIDIOC_OMAP3ISP_AEWB_CFG, VIDIOC_OMAP3ISP_HIST_CFG and VIDIOC_OMAP3ISP_AF_CFG +----------------------------------------------------------------------------- + +Those IOCTLs are used to configure the modules. They require user applications +to have an in-depth knowledge of the hardware. Most of the fields explanation +can be found on OMAP's TRMs. The two following fields common to all the above +configure private IOCTLs require explanation for better understanding as they +are not part of the TRM. + +omap3isp_[h3a_af/h3a_aewb/hist]\_config.buf_size: + +The modules handle their buffers internally. The necessary buffer size for the +module's data output depends on the requested configuration. Although the +driver supports reconfiguration while streaming, it does not support a +reconfiguration which requires bigger buffer size than what is already +internally allocated if the module is enabled. It will return -EBUSY on this +case. In order to avoid such condition, either disable/reconfigure/enable the +module or request the necessary buffer size during the first configuration +while the module is disabled. + +The internal buffer size allocation considers the requested configuration's +minimum buffer size and the value set on buf_size field. If buf_size field is +out of [minimum, maximum] buffer size range, it's clamped to fit in there. +The driver then selects the biggest value. The corrected buf_size value is +written back to user application. + +omap3isp_[h3a_af/h3a_aewb/hist]\_config.config_counter: + +As the configuration doesn't take effect synchronously to the request, the +driver must provide a way to track this information to provide more accurate +data. After a configuration is requested, the config_counter returned to user +space application will be an unique value associated to that request. When +user application receives an event for buffer availability or when a new +buffer is requested, this config_counter is used to match a buffer data and a +configuration. + +VIDIOC_OMAP3ISP_STAT_REQ +------------------------ + +Send to user space the oldest data available in the internal buffer queue and +discards such buffer afterwards. The field omap3isp_stat_data.frame_number +matches with the video buffer's field_count. + + +References +---------- + +.. [#] include/linux/omap3isp.h |