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1 | Samsung S5P/EXYNOS4 FIMC driver |
2 | ||
188ab116 | 3 | Copyright (C) 2012 - 2013 Samsung Electronics Co., Ltd. |
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4 | --------------------------------------------------------------------------- |
5 | ||
6 | The FIMC (Fully Interactive Mobile Camera) device available in Samsung | |
7 | SoC Application Processors is an integrated camera host interface, color | |
8 | space converter, image resizer and rotator. It's also capable of capturing | |
9 | data from LCD controller (FIMD) through the SoC internal writeback data | |
10 | path. There are multiple FIMC instances in the SoCs (up to 4), having | |
11 | slightly different capabilities, like pixel alignment constraints, rotator | |
12 | availability, LCD writeback support, etc. The driver is located at | |
188ab116 | 13 | drivers/media/platform/exynos4-is directory. |
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14 | |
15 | 1. Supported SoCs | |
16 | ================= | |
17 | ||
18 | S5PC100 (mem-to-mem only), S5PV210, EXYNOS4210 | |
19 | ||
20 | 2. Supported features | |
21 | ===================== | |
22 | ||
23 | - camera parallel interface capture (ITU-R.BT601/565); | |
24 | - camera serial interface capture (MIPI-CSI2); | |
25 | - memory-to-memory processing (color space conversion, scaling, mirror | |
26 | and rotation); | |
27 | - dynamic pipeline re-configuration at runtime (re-attachment of any FIMC | |
28 | instance to any parallel video input or any MIPI-CSI front-end); | |
29 | - runtime PM and system wide suspend/resume | |
30 | ||
31 | Not currently supported: | |
32 | - LCD writeback input | |
33 | - per frame clock gating (mem-to-mem) | |
34 | ||
35 | 3. Files partitioning | |
36 | ===================== | |
37 | ||
38 | - media device driver | |
188ab116 | 39 | drivers/media/platform/exynos4-is/media-dev.[ch] |
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40 | |
41 | - camera capture video device driver | |
188ab116 | 42 | drivers/media/platform/exynos4-is/fimc-capture.c |
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43 | |
44 | - MIPI-CSI2 receiver subdev | |
188ab116 | 45 | drivers/media/platform/exynos4-is/mipi-csis.[ch] |
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46 | |
47 | - video post-processor (mem-to-mem) | |
188ab116 | 48 | drivers/media/platform/exynos4-is/fimc-core.c |
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49 | |
50 | - common files | |
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51 | drivers/media/platform/exynos4-is/fimc-core.h |
52 | drivers/media/platform/exynos4-is/fimc-reg.h | |
53 | drivers/media/platform/exynos4-is/regs-fimc.h | |
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54 | |
55 | 4. User space interfaces | |
56 | ======================== | |
57 | ||
58 | 4.1. Media device interface | |
59 | ||
60 | The driver supports Media Controller API as defined at | |
1c612e9a | 61 | http://linuxtv.org/downloads/v4l-dvb-apis/media_common.html |
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62 | The media device driver name is "SAMSUNG S5P FIMC". |
63 | ||
64 | The purpose of this interface is to allow changing assignment of FIMC instances | |
65 | to the SoC peripheral camera input at runtime and optionally to control internal | |
66 | connections of the MIPI-CSIS device(s) to the FIMC entities. | |
67 | ||
68 | The media device interface allows to configure the SoC for capturing image | |
69 | data from the sensor through more than one FIMC instance (e.g. for simultaneous | |
70 | viewfinder and still capture setup). | |
71 | Reconfiguration is done by enabling/disabling media links created by the driver | |
72 | during initialization. The internal device topology can be easily discovered | |
73 | through media entity and links enumeration. | |
74 | ||
75 | 4.2. Memory-to-memory video node | |
76 | ||
77 | V4L2 memory-to-memory interface at /dev/video? device node. This is standalone | |
78 | video device, it has no media pads. However please note the mem-to-mem and | |
79 | capture video node operation on same FIMC instance is not allowed. The driver | |
80 | detects such cases but the applications should prevent them to avoid an | |
81 | undefined behaviour. | |
82 | ||
83 | 4.3. Capture video node | |
84 | ||
85 | The driver supports V4L2 Video Capture Interface as defined at: | |
86 | http://linuxtv.org/downloads/v4l-dvb-apis/devices.html | |
87 | ||
88 | At the capture and mem-to-mem video nodes only the multi-planar API is | |
89 | supported. For more details see: | |
90 | http://linuxtv.org/downloads/v4l-dvb-apis/planar-apis.html | |
91 | ||
92 | 4.4. Camera capture subdevs | |
93 | ||
94 | Each FIMC instance exports a sub-device node (/dev/v4l-subdev?), a sub-device | |
95 | node is also created per each available and enabled at the platform level | |
96 | MIPI-CSI receiver device (currently up to two). | |
97 | ||
98 | 4.5. sysfs | |
99 | ||
100 | In order to enable more precise camera pipeline control through the sub-device | |
101 | API the driver creates a sysfs entry associated with "s5p-fimc-md" platform | |
102 | device. The entry path is: /sys/platform/devices/s5p-fimc-md/subdev_conf_mode. | |
103 | ||
104 | In typical use case there could be a following capture pipeline configuration: | |
105 | sensor subdev -> mipi-csi subdev -> fimc subdev -> video node | |
106 | ||
107 | When we configure these devices through sub-device API at user space, the | |
108 | configuration flow must be from left to right, and the video node is | |
109 | configured as last one. | |
110 | When we don't use sub-device user space API the whole configuration of all | |
111 | devices belonging to the pipeline is done at the video node driver. | |
112 | The sysfs entry allows to instruct the capture node driver not to configure | |
113 | the sub-devices (format, crop), to avoid resetting the subdevs' configuration | |
114 | when the last configuration steps at the video node is performed. | |
115 | ||
116 | For full sub-device control support (subdevs configured at user space before | |
117 | starting streaming): | |
118 | # echo "sub-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode | |
119 | ||
120 | For V4L2 video node control only (subdevs configured internally by the host | |
121 | driver): | |
122 | # echo "vid-dev" > /sys/platform/devices/s5p-fimc-md/subdev_conf_mode | |
123 | This is a default option. | |
124 | ||
125 | 5. Device mapping to video and subdev device nodes | |
126 | ================================================== | |
127 | ||
128 | There are associated two video device nodes with each device instance in | |
129 | hardware - video capture and mem-to-mem and additionally a subdev node for | |
130 | more precise FIMC capture subsystem control. In addition a separate v4l2 | |
131 | sub-device node is created per each MIPI-CSIS device. | |
132 | ||
133 | How to find out which /dev/video? or /dev/v4l-subdev? is assigned to which | |
134 | device? | |
135 | ||
136 | You can either grep through the kernel log to find relevant information, i.e. | |
137 | # dmesg | grep -i fimc | |
138 | (note that udev, if present, might still have rearranged the video nodes), | |
139 | ||
140 | or retrieve the information from /dev/media? with help of the media-ctl tool: | |
141 | # media-ctl -p | |
142 | ||
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143 | 7. Build |
144 | ======== | |
145 | ||
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146 | If the driver is built as a loadable kernel module (CONFIG_VIDEO_SAMSUNG_S5P_FIMC=m) |
147 | two modules are created (in addition to the core v4l2 modules): s5p-fimc.ko and | |
148 | optional s5p-csis.ko (MIPI-CSI receiver subdev). |