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-OMAP 3 Image Signal Processor (ISP) driver
-
-Copyright (C) 2010 Nokia Corporation
-Copyright (C) 2009 Texas Instruments, Inc.
-
-Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
- Sakari Ailus <sakari.ailus@iki.fi>
- David Cohen <dacohen@gmail.com>
-
-
-Introduction
-============
-
-This file documents the Texas Instruments OMAP 3 Image Signal Processor (ISP)
-driver located under drivers/media/video/omap3isp. The original driver was
-written by Texas Instruments but since that it has been rewritten (twice) at
-Nokia.
-
-The driver has been successfully used on the following versions of OMAP 3:
-
- 3430
- 3530
- 3630
-
-The driver implements V4L2, Media controller and v4l2_subdev interfaces.
-Sensor, lens and flash drivers using the v4l2_subdev interface in the kernel
-are supported.
-
-
-Split to subdevs
-================
-
-The OMAP 3 ISP is split into V4L2 subdevs, each of the blocks inside the ISP
-having one subdev to represent it. Each of the subdevs provide a V4L2 subdev
-interface to userspace.
-
- OMAP3 ISP CCP2
- OMAP3 ISP CSI2a
- OMAP3 ISP CCDC
- OMAP3 ISP preview
- OMAP3 ISP resizer
- OMAP3 ISP AEWB
- OMAP3 ISP AF
- OMAP3 ISP histogram
-
-Each possible link in the ISP is modelled by a link in the Media controller
-interface. For an example program see [2].
-
-
-Controlling the OMAP 3 ISP
-==========================
-
-In general, the settings given to the OMAP 3 ISP take effect at the beginning
-of the following frame. This is done when the module becomes idle during the
-vertical blanking period on the sensor. In memory-to-memory operation the pipe
-is run one frame at a time. Applying the settings is done between the frames.
-
-All the blocks in the ISP, excluding the CSI-2 and possibly the CCP2 receiver,
-insist on receiving complete frames. Sensors must thus never send the ISP
-partial frames.
-
-Autoidle does have issues with some ISP blocks on the 3430, at least.
-Autoidle is only enabled on 3630 when the omap3isp module parameter autoidle
-is non-zero.
-
-
-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 [1].
-
-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.
-
-
-Technical reference manuals (TRMs) and other documentation
-==========================================================
-
-OMAP 3430 TRM:
-<URL:http://focus.ti.com/pdfs/wtbu/OMAP34xx_ES3.1.x_PUBLIC_TRM_vZM.zip>
-Referenced 2011-03-05.
-
-OMAP 35xx TRM:
-<URL:http://www.ti.com/litv/pdf/spruf98o> Referenced 2011-03-05.
-
-OMAP 3630 TRM:
-<URL:http://focus.ti.com/pdfs/wtbu/OMAP36xx_ES1.x_PUBLIC_TRM_vQ.zip>
-Referenced 2011-03-05.
-
-DM 3730 TRM:
-<URL:http://www.ti.com/litv/pdf/sprugn4h> Referenced 2011-03-06.
-
-
-References
-==========
-
-[1] include/linux/omap3isp.h
-
-[2] http://git.ideasonboard.org/?p=media-ctl.git;a=summary