linux/drivers/iio/industrialio-gts-helper.c

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// SPDX-License-Identifier: GPL-2.0-only
/* gain-time-scale conversion helpers for IIO light sensors
*
* Copyright (c) 2023 Matti Vaittinen <mazziesaccount@gmail.com>
*/
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/overflow.h>
#include <linux/slab.h>
#include <linux/sort.h>
#include <linux/types.h>
#include <linux/units.h>
#include <linux/iio/iio-gts-helper.h>
#include <linux/iio/types.h>
/**
* iio_gts_get_gain - Convert scale to total gain
*
* Internal helper for converting scale to total gain.
*
* @max: Maximum linearized scale. As an example, when scale is created
* in magnitude of NANOs and max scale is 64.1 - The linearized
* scale is 64 100 000 000.
* @scale: Linearized scale to compute the gain for.
*
* Return: (floored) gain corresponding to the scale. -EINVAL if scale
* is invalid.
*/
static int iio_gts_get_gain(const u64 max, const u64 scale)
{
u64 full = max;
int tmp = 1;
if (scale > full || !scale)
return -EINVAL;
if (U64_MAX - full < scale) {
/* Risk of overflow */
if (full - scale < scale)
return 1;
full -= scale;
tmp++;
}
while (full > scale * (u64)tmp)
tmp++;
return tmp;
}
/**
* gain_get_scale_fraction - get the gain or time based on scale and known one
*
* @max: Maximum linearized scale. As an example, when scale is created
* in magnitude of NANOs and max scale is 64.1 - The linearized
* scale is 64 100 000 000.
* @scale: Linearized scale to compute the gain/time for.
* @known: Either integration time or gain depending on which one is known
* @unknown: Pointer to variable where the computed gain/time is stored
*
* Internal helper for computing unknown fraction of total gain.
* Compute either gain or time based on scale and either the gain or time
* depending on which one is known.
*
* Return: 0 on success.
*/
static int gain_get_scale_fraction(const u64 max, u64 scale, int known,
int *unknown)
{
int tot_gain;
tot_gain = iio_gts_get_gain(max, scale);
if (tot_gain < 0)
return tot_gain;
*unknown = tot_gain / known;
/* We require total gain to be exact multiple of known * unknown */
if (!*unknown || *unknown * known != tot_gain)
return -EINVAL;
return 0;
}
static int iio_gts_delinearize(u64 lin_scale, unsigned long scaler,
int *scale_whole, int *scale_nano)
{
int frac;
if (scaler > NANO)
return -EOVERFLOW;
if (!scaler)
return -EINVAL;
frac = do_div(lin_scale, scaler);
*scale_whole = lin_scale;
*scale_nano = frac * (NANO / scaler);
return 0;
}
static int iio_gts_linearize(int scale_whole, int scale_nano,
unsigned long scaler, u64 *lin_scale)
{
/*
* Expect scale to be (mostly) NANO or MICRO. Divide divider instead of
* multiplication followed by division to avoid overflow.
*/
if (scaler > NANO || !scaler)
return -EINVAL;
*lin_scale = (u64)scale_whole * (u64)scaler +
(u64)(scale_nano / (NANO / scaler));
return 0;
}
/**
* iio_gts_total_gain_to_scale - convert gain to scale
* @gts: Gain time scale descriptor
* @total_gain: the gain to be converted
* @scale_int: Pointer to integral part of the scale (typically val1)
* @scale_nano: Pointer to fractional part of the scale (nano or ppb)
*
* Convert the total gain value to scale. NOTE: This does not separate gain
* generated by HW-gain or integration time. It is up to caller to decide what
* part of the total gain is due to integration time and what due to HW-gain.
*
* Return: 0 on success. Negative errno on failure.
*/
int iio_gts_total_gain_to_scale(struct iio_gts *gts, int total_gain,
int *scale_int, int *scale_nano)
{
u64 tmp;
tmp = gts->max_scale;
do_div(tmp, total_gain);
return iio_gts_delinearize(tmp, NANO, scale_int, scale_nano);
}
EXPORT_SYMBOL_NS_GPL(iio_gts_total_gain_to_scale, IIO_GTS_HELPER);
/**
* iio_gts_purge_avail_scale_table - free-up the available scale tables
* @gts: Gain time scale descriptor
*
* Free the space reserved by iio_gts_build_avail_scale_table().
*/
static void iio_gts_purge_avail_scale_table(struct iio_gts *gts)
{
int i;
if (gts->per_time_avail_scale_tables) {
for (i = 0; i < gts->num_itime; i++)
kfree(gts->per_time_avail_scale_tables[i]);
kfree(gts->per_time_avail_scale_tables);
gts->per_time_avail_scale_tables = NULL;
}
kfree(gts->avail_all_scales_table);
gts->avail_all_scales_table = NULL;
gts->num_avail_all_scales = 0;
}
static int iio_gts_gain_cmp(const void *a, const void *b)
{
return *(int *)a - *(int *)b;
}
static int gain_to_scaletables(struct iio_gts *gts, int **gains, int **scales)
{
int ret, i, j, new_idx, time_idx;
int *all_gains;
size_t gain_bytes;
for (i = 0; i < gts->num_itime; i++) {
/*
* Sort the tables for nice output and for easier finding of
* unique values.
*/
sort(gains[i], gts->num_hwgain, sizeof(int), iio_gts_gain_cmp,
NULL);
/* Convert gains to scales */
for (j = 0; j < gts->num_hwgain; j++) {
ret = iio_gts_total_gain_to_scale(gts, gains[i][j],
&scales[i][2 * j],
&scales[i][2 * j + 1]);
if (ret)
return ret;
}
}
gain_bytes = array_size(gts->num_hwgain, sizeof(int));
all_gains = kcalloc(gts->num_itime, gain_bytes, GFP_KERNEL);
if (!all_gains)
return -ENOMEM;
/*
* We assume all the gains for same integration time were unique.
* It is likely the first time table had greatest time multiplier as
* the times are in the order of preference and greater times are
* usually preferred. Hence we start from the last table which is likely
* to have the smallest total gains.
*/
time_idx = gts->num_itime - 1;
memcpy(all_gains, gains[time_idx], gain_bytes);
new_idx = gts->num_hwgain;
while (time_idx--) {
for (j = 0; j < gts->num_hwgain; j++) {
int candidate = gains[time_idx][j];
int chk;
if (candidate > all_gains[new_idx - 1]) {
all_gains[new_idx] = candidate;
new_idx++;
continue;
}
for (chk = 0; chk < new_idx; chk++)
if (candidate <= all_gains[chk])
break;
if (candidate == all_gains[chk])
continue;
memmove(&all_gains[chk + 1], &all_gains[chk],
(new_idx - chk) * sizeof(int));
all_gains[chk] = candidate;
new_idx++;
}
}
gts->avail_all_scales_table = kcalloc(new_idx, 2 * sizeof(int),
GFP_KERNEL);
if (!gts->avail_all_scales_table) {
ret = -ENOMEM;
goto free_out;
}
gts->num_avail_all_scales = new_idx;
for (i = 0; i < gts->num_avail_all_scales; i++) {
ret = iio_gts_total_gain_to_scale(gts, all_gains[i],
&gts->avail_all_scales_table[i * 2],
&gts->avail_all_scales_table[i * 2 + 1]);
if (ret) {
kfree(gts->avail_all_scales_table);
gts->num_avail_all_scales = 0;
goto free_out;
}
}
free_out:
kfree(all_gains);
return ret;
}
/**
* iio_gts_build_avail_scale_table - create tables of available scales
* @gts: Gain time scale descriptor
*
* Build the tables which can represent the available scales based on the
* originally given gain and time tables. When both time and gain tables are
* given this results:
* 1. A set of tables representing available scales for each supported
* integration time.
* 2. A single table listing all the unique scales that any combination of
* supported gains and times can provide.
*
* NOTE: Space allocated for the tables must be freed using
* iio_gts_purge_avail_scale_table() when the tables are no longer needed.
*
* Return: 0 on success.
*/
static int iio_gts_build_avail_scale_table(struct iio_gts *gts)
{
int **per_time_gains, **per_time_scales, i, j, ret = -ENOMEM;
per_time_gains = kcalloc(gts->num_itime, sizeof(*per_time_gains), GFP_KERNEL);
if (!per_time_gains)
return ret;
per_time_scales = kcalloc(gts->num_itime, sizeof(*per_time_scales), GFP_KERNEL);
if (!per_time_scales)
goto free_gains;
for (i = 0; i < gts->num_itime; i++) {
per_time_scales[i] = kcalloc(gts->num_hwgain, 2 * sizeof(int),
GFP_KERNEL);
if (!per_time_scales[i])
goto err_free_out;
per_time_gains[i] = kcalloc(gts->num_hwgain, sizeof(int),
GFP_KERNEL);
if (!per_time_gains[i]) {
kfree(per_time_scales[i]);
goto err_free_out;
}
for (j = 0; j < gts->num_hwgain; j++)
per_time_gains[i][j] = gts->hwgain_table[j].gain *
gts->itime_table[i].mul;
}
ret = gain_to_scaletables(gts, per_time_gains, per_time_scales);
if (ret)
goto err_free_out;
kfree(per_time_gains);
gts->per_time_avail_scale_tables = per_time_scales;
return 0;
err_free_out:
for (i--; i; i--) {
kfree(per_time_scales[i]);
kfree(per_time_gains[i]);
}
kfree(per_time_scales);
free_gains:
kfree(per_time_gains);
return ret;
}
static void iio_gts_us_to_int_micro(int *time_us, int *int_micro_times,
int num_times)
{
int i;
for (i = 0; i < num_times; i++) {
int_micro_times[i * 2] = time_us[i] / 1000000;
int_micro_times[i * 2 + 1] = time_us[i] % 1000000;
}
}
/**
* iio_gts_build_avail_time_table - build table of available integration times
* @gts: Gain time scale descriptor
*
* Build the table which can represent the available times to be returned
* to users using the read_avail-callback.
*
* NOTE: Space allocated for the tables must be freed using
* iio_gts_purge_avail_time_table() when the tables are no longer needed.
*
* Return: 0 on success.
*/
static int iio_gts_build_avail_time_table(struct iio_gts *gts)
{
int *times, i, j, idx = 0, *int_micro_times;
if (!gts->num_itime)
return 0;
times = kcalloc(gts->num_itime, sizeof(int), GFP_KERNEL);
if (!times)
return -ENOMEM;
/* Sort times from all tables to one and remove duplicates */
for (i = gts->num_itime - 1; i >= 0; i--) {
int new = gts->itime_table[i].time_us;
if (times[idx] < new) {
times[idx++] = new;
continue;
}
for (j = 0; j <= idx; j++) {
if (times[j] > new) {
memmove(&times[j + 1], &times[j],
(idx - j) * sizeof(int));
times[j] = new;
idx++;
}
}
}
/* create a list of times formatted as list of IIO_VAL_INT_PLUS_MICRO */
int_micro_times = kcalloc(idx, sizeof(int) * 2, GFP_KERNEL);
if (int_micro_times) {
/*
* This is just to survive a unlikely corner-case where times in
* the given time table were not unique. Else we could just
* trust the gts->num_itime.
*/
gts->num_avail_time_tables = idx;
iio_gts_us_to_int_micro(times, int_micro_times, idx);
}
gts->avail_time_tables = int_micro_times;
kfree(times);
if (!int_micro_times)
return -ENOMEM;
return 0;
}
/**
* iio_gts_purge_avail_time_table - free-up the available integration time table
* @gts: Gain time scale descriptor
*
* Free the space reserved by iio_gts_build_avail_time_table().
*/
static void iio_gts_purge_avail_time_table(struct iio_gts *gts)
{
if (gts->num_avail_time_tables) {
kfree(gts->avail_time_tables);
gts->avail_time_tables = NULL;
gts->num_avail_time_tables = 0;
}
}
/**
* iio_gts_build_avail_tables - create tables of available scales and int times
* @gts: Gain time scale descriptor
*
* Build the tables which can represent the available scales and available
* integration times. Availability tables are built based on the originally
* given gain and given time tables.
*
* When both time and gain tables are
* given this results:
* 1. A set of sorted tables representing available scales for each supported
* integration time.
* 2. A single sorted table listing all the unique scales that any combination
* of supported gains and times can provide.
* 3. A sorted table of supported integration times
*
* After these tables are built one can use the iio_gts_all_avail_scales(),
* iio_gts_avail_scales_for_time() and iio_gts_avail_times() helpers to
* implement the read_avail operations.
*
* NOTE: Space allocated for the tables must be freed using
* iio_gts_purge_avail_tables() when the tables are no longer needed.
*
* Return: 0 on success.
*/
static int iio_gts_build_avail_tables(struct iio_gts *gts)
{
int ret;
ret = iio_gts_build_avail_scale_table(gts);
if (ret)
return ret;
ret = iio_gts_build_avail_time_table(gts);
if (ret)
iio_gts_purge_avail_scale_table(gts);
return ret;
}
/**
* iio_gts_purge_avail_tables - free-up the availability tables
* @gts: Gain time scale descriptor
*
* Free the space reserved by iio_gts_build_avail_tables(). Frees both the
* integration time and scale tables.
*/
static void iio_gts_purge_avail_tables(struct iio_gts *gts)
{
iio_gts_purge_avail_time_table(gts);
iio_gts_purge_avail_scale_table(gts);
}
static void devm_iio_gts_avail_all_drop(void *res)
{
iio_gts_purge_avail_tables(res);
}
/**
* devm_iio_gts_build_avail_tables - manged add availability tables
* @dev: Pointer to the device whose lifetime tables are bound
* @gts: Gain time scale descriptor
*
* Build the tables which can represent the available scales and available
* integration times. Availability tables are built based on the originally
* given gain and given time tables.
*
* When both time and gain tables are given this results:
* 1. A set of sorted tables representing available scales for each supported
* integration time.
* 2. A single sorted table listing all the unique scales that any combination
* of supported gains and times can provide.
* 3. A sorted table of supported integration times
*
* After these tables are built one can use the iio_gts_all_avail_scales(),
* iio_gts_avail_scales_for_time() and iio_gts_avail_times() helpers to
* implement the read_avail operations.
*
* The tables are automatically released upon device detach.
*
* Return: 0 on success.
*/
static int devm_iio_gts_build_avail_tables(struct device *dev,
struct iio_gts *gts)
{
int ret;
ret = iio_gts_build_avail_tables(gts);
if (ret)
return ret;
return devm_add_action_or_reset(dev, devm_iio_gts_avail_all_drop, gts);
}
static int sanity_check_time(const struct iio_itime_sel_mul *t)
{
if (t->sel < 0 || t->time_us < 0 || t->mul <= 0)
return -EINVAL;
return 0;
}
static int sanity_check_gain(const struct iio_gain_sel_pair *g)
{
if (g->sel < 0 || g->gain <= 0)
return -EINVAL;
return 0;
}
static int iio_gts_sanity_check(struct iio_gts *gts)
{
int g, t, ret;
if (!gts->num_hwgain && !gts->num_itime)
return -EINVAL;
for (t = 0; t < gts->num_itime; t++) {
ret = sanity_check_time(&gts->itime_table[t]);
if (ret)
return ret;
}
for (g = 0; g < gts->num_hwgain; g++) {
ret = sanity_check_gain(&gts->hwgain_table[g]);
if (ret)
return ret;
}
for (g = 0; g < gts->num_hwgain; g++) {
for (t = 0; t < gts->num_itime; t++) {
int gain, mul, res;
gain = gts->hwgain_table[g].gain;
mul = gts->itime_table[t].mul;
if (check_mul_overflow(gain, mul, &res))
return -EOVERFLOW;
}
}
return 0;
}
static int iio_init_iio_gts(int max_scale_int, int max_scale_nano,
const struct iio_gain_sel_pair *gain_tbl, int num_gain,
const struct iio_itime_sel_mul *tim_tbl, int num_times,
struct iio_gts *gts)
{
int ret;
memset(gts, 0, sizeof(*gts));
ret = iio_gts_linearize(max_scale_int, max_scale_nano, NANO,
&gts->max_scale);
if (ret)
return ret;
gts->hwgain_table = gain_tbl;
gts->num_hwgain = num_gain;
gts->itime_table = tim_tbl;
gts->num_itime = num_times;
return iio_gts_sanity_check(gts);
}
/**
* devm_iio_init_iio_gts - Initialize the gain-time-scale helper
* @dev: Pointer to the device whose lifetime gts resources are
* bound
* @max_scale_int: integer part of the maximum scale value
* @max_scale_nano: fraction part of the maximum scale value
* @gain_tbl: table describing supported gains
* @num_gain: number of gains in the gain table
* @tim_tbl: table describing supported integration times. Provide
* the integration time table sorted so that the preferred
* integration time is in the first array index. The search
* functions like the
* iio_gts_find_time_and_gain_sel_for_scale() start search
* from first provided time.
* @num_times: number of times in the time table
* @gts: pointer to the helper struct
*
* Initialize the gain-time-scale helper for use. Note, gains, times, selectors
* and multipliers must be positive. Negative values are reserved for error
* checking. The total gain (maximum gain * maximum time multiplier) must not
* overflow int. The allocated resources will be released upon device detach.
*
* Return: 0 on success.
*/
int devm_iio_init_iio_gts(struct device *dev, int max_scale_int, int max_scale_nano,
const struct iio_gain_sel_pair *gain_tbl, int num_gain,
const struct iio_itime_sel_mul *tim_tbl, int num_times,
struct iio_gts *gts)
{
int ret;
ret = iio_init_iio_gts(max_scale_int, max_scale_nano, gain_tbl,
num_gain, tim_tbl, num_times, gts);
if (ret)
return ret;
return devm_iio_gts_build_avail_tables(dev, gts);
}
EXPORT_SYMBOL_NS_GPL(devm_iio_init_iio_gts, IIO_GTS_HELPER);
/**
* iio_gts_all_avail_scales - helper for listing all available scales
* @gts: Gain time scale descriptor
* @vals: Returned array of supported scales
* @type: Type of returned scale values
* @length: Amount of returned values in array
*
* Return: a value suitable to be returned from read_avail or a negative error.
*/
int iio_gts_all_avail_scales(struct iio_gts *gts, const int **vals, int *type,
int *length)
{
if (!gts->num_avail_all_scales)
return -EINVAL;
*vals = gts->avail_all_scales_table;
*type = IIO_VAL_INT_PLUS_NANO;
*length = gts->num_avail_all_scales * 2;
return IIO_AVAIL_LIST;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_all_avail_scales, IIO_GTS_HELPER);
/**
* iio_gts_avail_scales_for_time - list scales for integration time
* @gts: Gain time scale descriptor
* @time: Integration time for which the scales are listed
* @vals: Returned array of supported scales
* @type: Type of returned scale values
* @length: Amount of returned values in array
*
* Drivers which do not allow scale setting to change integration time can
* use this helper to list only the scales which are valid for given integration
* time.
*
* Return: a value suitable to be returned from read_avail or a negative error.
*/
int iio_gts_avail_scales_for_time(struct iio_gts *gts, int time,
const int **vals, int *type, int *length)
{
int i;
for (i = 0; i < gts->num_itime; i++)
if (gts->itime_table[i].time_us == time)
break;
if (i == gts->num_itime)
return -EINVAL;
*vals = gts->per_time_avail_scale_tables[i];
*type = IIO_VAL_INT_PLUS_NANO;
*length = gts->num_hwgain * 2;
return IIO_AVAIL_LIST;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_avail_scales_for_time, IIO_GTS_HELPER);
/**
* iio_gts_avail_times - helper for listing available integration times
* @gts: Gain time scale descriptor
* @vals: Returned array of supported times
* @type: Type of returned scale values
* @length: Amount of returned values in array
*
* Return: a value suitable to be returned from read_avail or a negative error.
*/
int iio_gts_avail_times(struct iio_gts *gts, const int **vals, int *type,
int *length)
{
if (!gts->num_avail_time_tables)
return -EINVAL;
*vals = gts->avail_time_tables;
*type = IIO_VAL_INT_PLUS_MICRO;
*length = gts->num_avail_time_tables * 2;
return IIO_AVAIL_LIST;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_avail_times, IIO_GTS_HELPER);
/**
* iio_gts_find_sel_by_gain - find selector corresponding to a HW-gain
* @gts: Gain time scale descriptor
* @gain: HW-gain for which matching selector is searched for
*
* Return: a selector matching given HW-gain or -EINVAL if selector was
* not found.
*/
int iio_gts_find_sel_by_gain(struct iio_gts *gts, int gain)
{
int i;
for (i = 0; i < gts->num_hwgain; i++)
if (gts->hwgain_table[i].gain == gain)
return gts->hwgain_table[i].sel;
return -EINVAL;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_find_sel_by_gain, IIO_GTS_HELPER);
/**
* iio_gts_find_gain_by_sel - find HW-gain corresponding to a selector
* @gts: Gain time scale descriptor
* @sel: selector for which matching HW-gain is searched for
*
* Return: a HW-gain matching given selector or -EINVAL if HW-gain was not
* found.
*/
int iio_gts_find_gain_by_sel(struct iio_gts *gts, int sel)
{
int i;
for (i = 0; i < gts->num_hwgain; i++)
if (gts->hwgain_table[i].sel == sel)
return gts->hwgain_table[i].gain;
return -EINVAL;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_find_gain_by_sel, IIO_GTS_HELPER);
/**
* iio_gts_get_min_gain - find smallest valid HW-gain
* @gts: Gain time scale descriptor
*
* Return: The smallest HW-gain -EINVAL if no HW-gains were in the tables.
*/
int iio_gts_get_min_gain(struct iio_gts *gts)
{
int i, min = -EINVAL;
for (i = 0; i < gts->num_hwgain; i++) {
int gain = gts->hwgain_table[i].gain;
if (min == -EINVAL)
min = gain;
else
min = min(min, gain);
}
return min;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_get_min_gain, IIO_GTS_HELPER);
/**
* iio_find_closest_gain_low - Find the closest lower matching gain
* @gts: Gain time scale descriptor
* @gain: HW-gain for which the closest match is searched
* @in_range: indicate if the @gain was actually in the range of
* supported gains.
*
* Search for closest supported gain that is lower than or equal to the
* gain given as a parameter. This is usable for drivers which do not require
* user to request exact matching gain but rather for rounding to a supported
* gain value which is equal or lower (setting lower gain is typical for
* avoiding saturation)
*
* Return: The closest matching supported gain or -EINVAL if @gain
* was smaller than the smallest supported gain.
*/
int iio_find_closest_gain_low(struct iio_gts *gts, int gain, bool *in_range)
{
int i, diff = 0;
int best = -1;
*in_range = false;
for (i = 0; i < gts->num_hwgain; i++) {
if (gain == gts->hwgain_table[i].gain) {
*in_range = true;
return gain;
}
if (gain > gts->hwgain_table[i].gain) {
if (!diff) {
diff = gain - gts->hwgain_table[i].gain;
best = i;
} else {
int tmp = gain - gts->hwgain_table[i].gain;
if (tmp < diff) {
diff = tmp;
best = i;
}
}
} else {
/*
* We found valid HW-gain which is greater than
* reference. So, unless we return a failure below we
* will have found an in-range gain
*/
*in_range = true;
}
}
/* The requested gain was smaller than anything we support */
if (!diff) {
*in_range = false;
return -EINVAL;
}
return gts->hwgain_table[best].gain;
}
EXPORT_SYMBOL_NS_GPL(iio_find_closest_gain_low, IIO_GTS_HELPER);
static int iio_gts_get_int_time_gain_multiplier_by_sel(struct iio_gts *gts,
int sel)
{
const struct iio_itime_sel_mul *time;
time = iio_gts_find_itime_by_sel(gts, sel);
if (!time)
return -EINVAL;
return time->mul;
}
/**
* iio_gts_find_gain_for_scale_using_time - Find gain by time and scale
* @gts: Gain time scale descriptor
* @time_sel: Integration time selector corresponding to the time gain is
* searched for
* @scale_int: Integral part of the scale (typically val1)
* @scale_nano: Fractional part of the scale (nano or ppb)
* @gain: Pointer to value where gain is stored.
*
* In some cases the light sensors may want to find a gain setting which
* corresponds given scale and integration time. Sensors which fill the
* gain and time tables may use this helper to retrieve the gain.
*
* Return: 0 on success. -EINVAL if gain matching the parameters is not
* found.
*/
static int iio_gts_find_gain_for_scale_using_time(struct iio_gts *gts, int time_sel,
int scale_int, int scale_nano,
int *gain)
{
u64 scale_linear;
int ret, mul;
ret = iio_gts_linearize(scale_int, scale_nano, NANO, &scale_linear);
if (ret)
return ret;
ret = iio_gts_get_int_time_gain_multiplier_by_sel(gts, time_sel);
if (ret < 0)
return ret;
mul = ret;
ret = gain_get_scale_fraction(gts->max_scale, scale_linear, mul, gain);
if (ret)
return ret;
if (!iio_gts_valid_gain(gts, *gain))
return -EINVAL;
return 0;
}
/**
* iio_gts_find_gain_sel_for_scale_using_time - Fetch gain selector.
* @gts: Gain time scale descriptor
* @time_sel: Integration time selector corresponding to the time gain is
* searched for
* @scale_int: Integral part of the scale (typically val1)
* @scale_nano: Fractional part of the scale (nano or ppb)
* @gain_sel: Pointer to value where gain selector is stored.
*
* See iio_gts_find_gain_for_scale_using_time() for more information
*/
int iio_gts_find_gain_sel_for_scale_using_time(struct iio_gts *gts, int time_sel,
int scale_int, int scale_nano,
int *gain_sel)
{
int gain, ret;
ret = iio_gts_find_gain_for_scale_using_time(gts, time_sel, scale_int,
scale_nano, &gain);
if (ret)
return ret;
ret = iio_gts_find_sel_by_gain(gts, gain);
if (ret < 0)
return ret;
*gain_sel = ret;
return 0;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_find_gain_sel_for_scale_using_time, IIO_GTS_HELPER);
static int iio_gts_get_total_gain(struct iio_gts *gts, int gain, int time)
{
const struct iio_itime_sel_mul *itime;
if (!iio_gts_valid_gain(gts, gain))
return -EINVAL;
if (!gts->num_itime)
return gain;
itime = iio_gts_find_itime_by_time(gts, time);
if (!itime)
return -EINVAL;
return gain * itime->mul;
}
static int iio_gts_get_scale_linear(struct iio_gts *gts, int gain, int time,
u64 *scale)
{
int total_gain;
u64 tmp;
total_gain = iio_gts_get_total_gain(gts, gain, time);
if (total_gain < 0)
return total_gain;
tmp = gts->max_scale;
do_div(tmp, total_gain);
*scale = tmp;
return 0;
}
/**
* iio_gts_get_scale - get scale based on integration time and HW-gain
* @gts: Gain time scale descriptor
* @gain: HW-gain for which the scale is computed
* @time: Integration time for which the scale is computed
* @scale_int: Integral part of the scale (typically val1)
* @scale_nano: Fractional part of the scale (nano or ppb)
*
* Compute scale matching the integration time and HW-gain given as parameter.
*
* Return: 0 on success.
*/
int iio_gts_get_scale(struct iio_gts *gts, int gain, int time, int *scale_int,
int *scale_nano)
{
u64 lin_scale;
int ret;
ret = iio_gts_get_scale_linear(gts, gain, time, &lin_scale);
if (ret)
return ret;
return iio_gts_delinearize(lin_scale, NANO, scale_int, scale_nano);
}
EXPORT_SYMBOL_NS_GPL(iio_gts_get_scale, IIO_GTS_HELPER);
/**
* iio_gts_find_new_gain_sel_by_old_gain_time - compensate for time change
* @gts: Gain time scale descriptor
* @old_gain: Previously set gain
* @old_time_sel: Selector corresponding previously set time
* @new_time_sel: Selector corresponding new time to be set
* @new_gain: Pointer to value where new gain is to be written
*
* We may want to mitigate the scale change caused by setting a new integration
* time (for a light sensor) by also updating the (HW)gain. This helper computes
* new gain value to maintain the scale with new integration time.
*
* Return: 0 if an exactly matching supported new gain was found. When a
* non-zero value is returned, the @new_gain will be set to a negative or
* positive value. The negative value means that no gain could be computed.
* Positive value will be the "best possible new gain there could be". There
* can be two reasons why finding the "best possible" new gain is not deemed
* successful. 1) This new value cannot be supported by the hardware. 2) The new
* gain required to maintain the scale would not be an integer. In this case,
* the "best possible" new gain will be a floored optimal gain, which may or
* may not be supported by the hardware.
*/
int iio_gts_find_new_gain_sel_by_old_gain_time(struct iio_gts *gts,
int old_gain, int old_time_sel,
int new_time_sel, int *new_gain)
{
const struct iio_itime_sel_mul *itime_old, *itime_new;
u64 scale;
int ret;
*new_gain = -1;
itime_old = iio_gts_find_itime_by_sel(gts, old_time_sel);
if (!itime_old)
return -EINVAL;
itime_new = iio_gts_find_itime_by_sel(gts, new_time_sel);
if (!itime_new)
return -EINVAL;
ret = iio_gts_get_scale_linear(gts, old_gain, itime_old->time_us,
&scale);
if (ret)
return ret;
ret = gain_get_scale_fraction(gts->max_scale, scale, itime_new->mul,
new_gain);
if (ret)
return ret;
if (!iio_gts_valid_gain(gts, *new_gain))
return -EINVAL;
return 0;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_find_new_gain_sel_by_old_gain_time, IIO_GTS_HELPER);
/**
* iio_gts_find_new_gain_by_old_gain_time - compensate for time change
* @gts: Gain time scale descriptor
* @old_gain: Previously set gain
* @old_time: Selector corresponding previously set time
* @new_time: Selector corresponding new time to be set
* @new_gain: Pointer to value where new gain is to be written
*
* We may want to mitigate the scale change caused by setting a new integration
* time (for a light sensor) by also updating the (HW)gain. This helper computes
* new gain value to maintain the scale with new integration time.
*
* Return: 0 if an exactly matching supported new gain was found. When a
* non-zero value is returned, the @new_gain will be set to a negative or
* positive value. The negative value means that no gain could be computed.
* Positive value will be the "best possible new gain there could be". There
* can be two reasons why finding the "best possible" new gain is not deemed
* successful. 1) This new value cannot be supported by the hardware. 2) The new
* gain required to maintain the scale would not be an integer. In this case,
* the "best possible" new gain will be a floored optimal gain, which may or
* may not be supported by the hardware.
*/
int iio_gts_find_new_gain_by_old_gain_time(struct iio_gts *gts, int old_gain,
int old_time, int new_time,
int *new_gain)
{
const struct iio_itime_sel_mul *itime_new;
u64 scale;
int ret;
*new_gain = -1;
itime_new = iio_gts_find_itime_by_time(gts, new_time);
if (!itime_new)
return -EINVAL;
ret = iio_gts_get_scale_linear(gts, old_gain, old_time, &scale);
if (ret)
return ret;
ret = gain_get_scale_fraction(gts->max_scale, scale, itime_new->mul,
new_gain);
if (ret)
return ret;
if (!iio_gts_valid_gain(gts, *new_gain))
return -EINVAL;
return 0;
}
EXPORT_SYMBOL_NS_GPL(iio_gts_find_new_gain_by_old_gain_time, IIO_GTS_HELPER);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>");
MODULE_DESCRIPTION("IIO light sensor gain-time-scale helpers");