[media] s5p-fimc: Add driver documentation
Add short documentation providing the driver usage details. Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Sylwester Nawrocki
Mauro Carvalho Chehab
parent
15f4bc3b1f
commit
1b741bc3db
178
Documentation/video4linux/fimc.txt
Normal file
178
Documentation/video4linux/fimc.txt
Normal file
@ -0,0 +1,178 @@
|
||||
Samsung S5P/EXYNOS4 FIMC driver
|
||||
|
||||
Copyright (C) 2012 Samsung Electronics Co., Ltd.
|
||||
---------------------------------------------------------------------------
|
||||
|
||||
The FIMC (Fully Interactive Mobile Camera) device available in Samsung
|
||||
SoC Application Processors is an integrated camera host interface, color
|
||||
space converter, image resizer and rotator. It's also capable of capturing
|
||||
data from LCD controller (FIMD) through the SoC internal writeback data
|
||||
path. There are multiple FIMC instances in the SoCs (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
|
||||
- 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 assignment of FIMC instances
|
||||
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 still capture setup).
|
||||
Reconfiguration is done by enabling/disabling 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 the video node driver.
|
||||
The sysfs entry allows to instruct the capture 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 is 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 a default option.
|
||||
|
||||
5. Device mapping to video and subdev device nodes
|
||||
==================================================
|
||||
|
||||
There are associated two video device nodes with each device instance in
|
||||
hardware - video capture and mem-to-mem and additionally a subdev node for
|
||||
more precise FIMC capture subsystem control. In addition a 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_FIMC /
|
||||
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,
|
||||
REGULATOR,
|
||||
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).
|
||||
Loading…
Reference in New Issue
Block a user