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Diffstat (limited to 'lib/v4l2.h')
| -rw-r--r-- | lib/v4l2.h | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/lib/v4l2.h b/lib/v4l2.h new file mode 100644 index 0000000..8d7b3c5 --- /dev/null +++ b/lib/v4l2.h @@ -0,0 +1,339 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * V4L2 Devices + * + * Copyright (C) 2018 Laurent Pinchart + * + * This file originally comes from the omap3-isp-live project + * (git://git.ideasonboard.org/omap3-isp-live.git) + * + * Copyright (C) 2010-2011 Ideas on board SPRL + * + * Contact: Laurent Pinchart <laurent.pinchart@ideasonboard.com> + */ +#ifndef __V4L2_H +#define __V4L2_H + +#include <linux/videodev2.h> +#include <stdint.h> + +#include "list.h" +#include "video-buffers.h" + +struct v4l2_device +{ + int fd; + char *name; + + enum v4l2_buf_type type; + enum v4l2_memory memtype; + + struct list_entry formats; + struct v4l2_pix_format format; + struct v4l2_rect crop; + + struct video_buffer_set buffers; +}; + +/* + * v4l2_open - Open a V4L2 device + * @devname: Name (including path) of the device node + * + * Open the V4L2 device referenced by @devname for video capture or display in + * non-blocking mode. + * + * If the device can be opened, query its capabilities and enumerates frame + * formats, sizes and intervals. + * + * Return a pointer to a newly allocated v4l2_device structure instance on + * success and NULL on failure. The returned pointer must be freed with + * v4l2_close when the device isn't needed anymore. + */ +struct v4l2_device *v4l2_open(const char *devname); + +/* + * v4l2_close - Close a V4L2 device + * @dev: Device instance + * + * Close the device instance given as argument and free allocated resources. + * Access to the device instance is forbidden after this function returns. + */ +void v4l2_close(struct v4l2_device *dev); + +/* + * v4l2_get_format - Retrieve the current pixel format + * @dev: Device instance + * @format: Pixel format structure to be filled + * + * Query the device to retrieve the current pixel format and frame size and fill + * the @format structure. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_get_format(struct v4l2_device *dev, struct v4l2_pix_format *format); + +/* + * v4l2_set_format - Set the pixel format + * @dev: Device instance + * @format: Pixel format structure to be set + * + * Set the pixel format and frame size stored in @format. The device can modify + * the requested format and size, in which case the @format structure will be + * updated to reflect the modified settings. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_set_format(struct v4l2_device *dev, struct v4l2_pix_format *format); + +/* + * v4l2_get_crop - Retrieve the current crop rectangle + * @dev: Device instance + * @rect: Crop rectangle structure to be filled + * + * Query the device to retrieve the current crop rectangle and fill the @rect + * structure. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_get_crop(struct v4l2_device *dev, struct v4l2_rect *rect); + +/* + * v4l2_set_crop - Set the crop rectangle + * @dev: Device instance + * @rect: Crop rectangle structure to be set + * + * Set the crop rectangle stored in @rect. The device can modify the requested + * rectangle, in which case the @rect structure will be updated to reflect the + * modified settings. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_set_crop(struct v4l2_device *dev, struct v4l2_rect *rect); + +/* + * v4l2_alloc_buffers - Allocate buffers for video frames + * @dev: Device instance + * @memtype: Type of buffers + * @nbufs: Number of buffers to allocate + * + * Request the driver to allocate @nbufs buffers. The driver can modify the + * number of buffers depending on its needs. The number of allocated buffers + * will be stored in the @dev->buffers.nbufs field. + * + * When @memtype is set to V4L2_MEMORY_MMAP the buffers are allocated by the + * driver. They can then be mapped to userspace by calling v4l2_mmap_buffers(). + * When @memtype is set to V4L2_MEMORY_DMABUF the driver only allocates buffer + * objects and relies on the application to provide memory storage for video + * frames. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_alloc_buffers(struct v4l2_device *dev, enum v4l2_memory memtype, + unsigned int nbufs); + +/* + * v4l2_free_buffers - Free buffers + * @dev: Device instance + * + * Free buffers previously allocated by v4l2_alloc_buffers(). If the buffers + * have been allocated with the V4L2_MEMORY_DMABUF memory type only the buffer + * objects are freed, and the caller is responsible for freeing the video frames + * memory if required. + * + * When successful this function sets the @dev->buffers.nbufs field to zero. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_free_buffers(struct v4l2_device *dev); + +/* + * v4l2_export_buffers - Export buffers as dmabuf objects + * @dev: Device instance + * + * Export all the buffers previously allocated by v4l2_alloc_buffers() as dmabuf + * objects. The dmabuf objects handles can be accessed through the dmabuf field + * of each entry in the @dev::buffers array. + * + * The dmabuf objects handles will be automatically closed when the buffers are + * freed with v4l2_free_buffers(). + * + * This function can only be called when buffers have been allocated with the + * memory type set to V4L2_MEMORY_MMAP. If the memory type is different, or if + * no buffers have been allocated, it will return -EINVAL. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_export_buffers(struct v4l2_device *dev); + +/* + * v4l2_import_buffers - Import buffer backing store as dmabuf objects + * @dev: Device instance + * @buffers: Buffers to be imported + * + * Import the dmabuf objects from @buffers as backing store for the device + * buffers previously allocated by v4l2_alloc_buffers(). + * + * The dmabuf file handles are duplicated and stored in the dmabuf field of the + * @dev::buffers array. The handles from the @buffers set can thus be closed + * independently without impacting usage of the imported dmabuf objects. The + * duplicated file handles will be automatically closed when the buffers are + * freed with v4l2_free_buffers(). + * + * This function can only be called when buffers have been allocated with the + * memory type set to V4L2_MEMORY_DMABUF. If the memory type is different, if no + * buffers have been allocated, or if the number of allocated buffers is larger + * than @buffers->nbufs, it will return -EINVAL. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_import_buffers(struct v4l2_device *dev, + const struct video_buffer_set *buffers); + +/* + * v4l2_mmap_buffers - Map buffers to application memory space + * @dev: Device instance + * + * Map all the buffers previously allocated by v4l2_alloc_buffers() to the + * application memory space. The buffer memory can be accessed through the mem + * field of each entry in the @dev::buffers array. + * + * Buffers will be automatically unmapped when freed with v4l2_free_buffers(). + * + * This function can only be called when buffers have been allocated with the + * memory type set to V4L2_MEMORY_MMAP. If the memory type is different, or if + * no buffers have been allocated, it will return -EINVAL. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_mmap_buffers(struct v4l2_device *dev); + +/* + * v4l2_queue_buffer - Queue a buffer for video capture/output + * @dev: Device instance + * @buffer: Buffer to be queued + * + * Queue the buffer identified by @buffer for video capture or output, depending + * on the device type. + * + * The caller must initialize the @buffer::index field with the index of the + * buffer to be queued. The index is zero-based and must be lower than the + * number of allocated buffers. + * + * For V4L2_MEMORY_DMABUF buffers, the caller must initialize the @buffer::dmabuf + * field with the address of the video frame memory, and the @buffer:length + * field with its size in bytes. For optimal performances the address and length + * should be identical between v4l2_queue_buffer() calls for a given buffer + * index. + * + * For video output, the caller must initialize the @buffer::bytesused field + * with the size of video data. The value should differ from the buffer length + * for variable-size video formats only. + * + * Upon successful return the buffer ownership is transferred to the driver. The + * caller must not touch video memory for that buffer before calling + * v4l2_dequeue_buffer(). Attempting to queue an already queued buffer will + * fail. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_queue_buffer(struct v4l2_device *dev, struct video_buffer *buffer); + +/* + * v4l2_dequeue_buffer - Dequeue the next buffer + * @dev: Device instance + * @buffer: Dequeued buffer data to be filled + * + * Dequeue the next buffer processed by the driver and fill all fields in + * @buffer. + * + * This function does not block. If no buffer is ready it will return + * immediately with -EAGAIN. + * + * If an error occured during video capture or display, the @buffer::error field + * is set to true. Depending on the device the video data can be partly + * corrupted or complete garbage. + * + * Once dequeued the buffer ownership is transferred to the caller. Video memory + * for that buffer can be safely read from and written to. + * + * Return 0 on success or a negative error code on failure. An error that + * results in @buffer:error being set is not considered as a failure condition + * for the purpose of the return value. + */ +int v4l2_dequeue_buffer(struct v4l2_device *dev, struct video_buffer *buffer); + +/* + * v4l2_stream_on - Start video streaming + * @dev: Device instance + * + * Start video capture or output on the device. For video output devices at + * least one buffer must be queued before starting the stream. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_stream_on(struct v4l2_device *dev); + +/* + * v4l2_stream_off - Stop video streaming + * @dev: Device instance + * + * Stop video capture or output on the device. Upon successful return ownership + * of all buffers is returned to the caller. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_stream_off(struct v4l2_device *dev); + +/* + * v4l2_get_control - Read the value of a control + * @dev: Device instance + * @id: Control ID + * @value: Control value to be filled + * + * Retrieve the current value of control @id and store it in @value. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_get_control(struct v4l2_device *dev, unsigned int id, int32_t *value); + +/* + * v4l2_set_control - Write the value of a control + * @dev: Device instance + * @id: Control ID + * @value: Control value + * + * Set control @id to @value. The device is allowed to modify the requested + * value, in which case @value is updated to the modified value. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_set_control(struct v4l2_device *dev, unsigned int id, int32_t *value); + +/* + * v4l2_get_controls - Read the value of multiple controls + * @dev: Device instance + * @count: Number of controls + * @ctrls: Controls to be read + * + * Retrieve the current value of controls identified by @ctrls. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_get_controls(struct v4l2_device *dev, unsigned int count, + struct v4l2_ext_control *ctrls); + +/* + * v4l2_set_controls - Write the value of multiple controls + * @dev: Device instance + * @count: Number of controls + * @ctrls: Controls to be written + * + * Set controls identified by @ctrls. The device is allowed to modify the + * requested values, in which case @ctrls is updated to the modified value. + * + * Return 0 on success or a negative error code on failure. + */ +int v4l2_set_controls(struct v4l2_device *dev, unsigned int count, + struct v4l2_ext_control *ctrls); + +#endif |