2.17. V4L2 DV Timings functions

struct v4l2_fract v4l2_calc_timeperframe(const struct v4l2_dv_timings *t)

helper function to calculate timeperframe based v4l2_dv_timings fields.

Parameters

const struct v4l2_dv_timings *t

Timings for the video mode.

Description

Calculates the expected timeperframe using the pixel clock value and horizontal/vertical measures. This means that v4l2_dv_timings structure must be correctly and fully filled.

v4l2_check_dv_timings_fnc

Typedef: timings check callback

Syntax

bool v4l2_check_dv_timings_fnc (const struct v4l2_dv_timings *t, void *handle)

Parameters

const struct v4l2_dv_timings *t

the v4l2_dv_timings struct.

void *handle

a handle from the driver.

Description

Returns true if the given timings are valid.

bool v4l2_valid_dv_timings(const struct v4l2_dv_timings *t, const struct v4l2_dv_timings_cap *cap, v4l2_check_dv_timings_fnc fnc, void *fnc_handle)

are these timings valid?

Parameters

const struct v4l2_dv_timings *t

the v4l2_dv_timings struct.

const struct v4l2_dv_timings_cap *cap

the v4l2_dv_timings_cap capabilities.

v4l2_check_dv_timings_fnc fnc

callback to check if this timing is OK. May be NULL.

void *fnc_handle

a handle that is passed on to fnc.

Description

Returns true if the given dv_timings struct is supported by the hardware capabilities and the callback function (if non-NULL), returns false otherwise.

int v4l2_enum_dv_timings_cap(struct v4l2_enum_dv_timings *t, const struct v4l2_dv_timings_cap *cap, v4l2_check_dv_timings_fnc fnc, void *fnc_handle)

Helper function to enumerate possible DV timings based on capabilities

Parameters

struct v4l2_enum_dv_timings *t

the v4l2_enum_dv_timings struct.

const struct v4l2_dv_timings_cap *cap

the v4l2_dv_timings_cap capabilities.

v4l2_check_dv_timings_fnc fnc

callback to check if this timing is OK. May be NULL.

void *fnc_handle

a handle that is passed on to fnc.

Description

This enumerates dv_timings using the full list of possible CEA-861 and DMT timings, filtering out any timings that are not supported based on the hardware capabilities and the callback function (if non-NULL).

If a valid timing for the given index is found, it will fill in t and return 0, otherwise it returns -EINVAL.

bool v4l2_find_dv_timings_cap(struct v4l2_dv_timings *t, const struct v4l2_dv_timings_cap *cap, unsigned pclock_delta, v4l2_check_dv_timings_fnc fnc, void *fnc_handle)

Find the closest timings struct

Parameters

struct v4l2_dv_timings *t

the v4l2_enum_dv_timings struct.

const struct v4l2_dv_timings_cap *cap

the v4l2_dv_timings_cap capabilities.

unsigned pclock_delta

maximum delta between t->pixelclock and the timing struct under consideration.

v4l2_check_dv_timings_fnc fnc

callback to check if a given timings struct is OK. May be NULL.

void *fnc_handle

a handle that is passed on to fnc.

Description

This function tries to map the given timings to an entry in the full list of possible CEA-861 and DMT timings, filtering out any timings that are not supported based on the hardware capabilities and the callback function (if non-NULL).

On success it will fill in t with the found timings and it returns true. On failure it will return false.

bool v4l2_find_dv_timings_cea861_vic(struct v4l2_dv_timings *t, u8 vic)

find timings based on CEA-861 VIC

Parameters

struct v4l2_dv_timings *t

the timings data.

u8 vic

CEA-861 VIC code

Description

On success it will fill in t with the found timings and it returns true. On failure it will return false.

bool v4l2_match_dv_timings(const struct v4l2_dv_timings *measured, const struct v4l2_dv_timings *standard, unsigned pclock_delta, bool match_reduced_fps)

do two timings match?

Parameters

const struct v4l2_dv_timings *measured

the measured timings data.

const struct v4l2_dv_timings *standard

the timings according to the standard.

unsigned pclock_delta

maximum delta in Hz between standard->pixelclock and the measured timings.

bool match_reduced_fps

if true, then fail if V4L2_DV_FL_REDUCED_FPS does not match.

Description

Returns true if the two timings match, returns false otherwise.

void v4l2_print_dv_timings(const char *dev_prefix, const char *prefix, const struct v4l2_dv_timings *t, bool detailed)

log the contents of a dv_timings struct

Parameters

const char *dev_prefix

device prefix for each log line.

const char *prefix

additional prefix for each log line, may be NULL.

const struct v4l2_dv_timings *t

the timings data.

bool detailed

if true, give a detailed log.

bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync, unsigned active_width, u32 polarities, bool interlaced, struct v4l2_dv_timings *fmt)

detect if the given timings follow the CVT standard

Parameters

unsigned frame_height

the total height of the frame (including blanking) in lines.

unsigned hfreq

the horizontal frequency in Hz.

unsigned vsync

the height of the vertical sync in lines.

unsigned active_width

active width of image (does not include blanking). This information is needed only in case of version 2 of reduced blanking. In other cases, this parameter does not have any effect on timings.

u32 polarities

the horizontal and vertical polarities (same as struct v4l2_bt_timings polarities).

bool interlaced

if this flag is true, it indicates interlaced format

struct v4l2_dv_timings *fmt

the resulting timings.

Description

This function will attempt to detect if the given values correspond to a valid CVT format. If so, then it will return true, and fmt will be filled in with the found CVT timings.

bool v4l2_detect_gtf(unsigned frame_height, unsigned hfreq, unsigned vsync, u32 polarities, bool interlaced, struct v4l2_fract aspect, struct v4l2_dv_timings *fmt)

detect if the given timings follow the GTF standard

Parameters

unsigned frame_height

the total height of the frame (including blanking) in lines.

unsigned hfreq

the horizontal frequency in Hz.

unsigned vsync

the height of the vertical sync in lines.

u32 polarities

the horizontal and vertical polarities (same as struct v4l2_bt_timings polarities).

bool interlaced

if this flag is true, it indicates interlaced format

struct v4l2_fract aspect

preferred aspect ratio. GTF has no method of determining the aspect ratio in order to derive the image width from the image height, so it has to be passed explicitly. Usually the native screen aspect ratio is used for this. If it is not filled in correctly, then 16:9 will be assumed.

struct v4l2_dv_timings *fmt

the resulting timings.

Description

This function will attempt to detect if the given values correspond to a valid GTF format. If so, then it will return true, and fmt will be filled in with the found GTF timings.

struct v4l2_fract v4l2_calc_aspect_ratio(u8 hor_landscape, u8 vert_portrait)

calculate the aspect ratio based on bytes 0x15 and 0x16 from the EDID.

Parameters

u8 hor_landscape

byte 0x15 from the EDID.

u8 vert_portrait

byte 0x16 from the EDID.

Description

Determines the aspect ratio from the EDID. See VESA Enhanced EDID standard, release A, rev 2, section 3.6.2: “Horizontal and Vertical Screen Size or Aspect Ratio”

struct v4l2_fract v4l2_dv_timings_aspect_ratio(const struct v4l2_dv_timings *t)

calculate the aspect ratio based on the v4l2_dv_timings information.

Parameters

const struct v4l2_dv_timings *t

the timings data.

bool can_reduce_fps(struct v4l2_bt_timings *bt)

check if conditions for reduced fps are true.

Parameters

struct v4l2_bt_timings *bt

v4l2 timing structure

Description

For different timings reduced fps is allowed if the following conditions are met:

• For CVT timings: if reduced blanking v2 (vsync == 8) is true.

• For CEA861 timings: if V4L2_DV_FL_CAN_REDUCE_FPS flag is true.

struct v4l2_hdmi_colorimetry

describes the HDMI colorimetry information

Definition:

struct v4l2_hdmi_colorimetry {
    enum v4l2_colorspace colorspace;
    enum v4l2_ycbcr_encoding ycbcr_enc;
    enum v4l2_quantization quantization;
    enum v4l2_xfer_func xfer_func;
};

Members

colorspace

enum v4l2_colorspace, the colorspace

ycbcr_enc

enum v4l2_ycbcr_encoding, Y’CbCr encoding

quantization

enum v4l2_quantization, colorspace quantization

xfer_func

enum v4l2_xfer_func, colorspace transfer function