diff options
Diffstat (limited to 'drivers/iio/industrialio-gts-helper.c')
| -rw-r--r-- | drivers/iio/industrialio-gts-helper.c | 1077 |
1 files changed, 1077 insertions, 0 deletions
diff --git a/drivers/iio/industrialio-gts-helper.c b/drivers/iio/industrialio-gts-helper.c new file mode 100644 index 000000000000..8bb68975b259 --- /dev/null +++ b/drivers/iio/industrialio-gts-helper.c @@ -0,0 +1,1077 @@ +// 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], + >s->avail_all_scales_table[i * 2], + >s->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; +} + +/** + * 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; + + 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(×[j + 1], ×[j], + (idx - j) * sizeof(int)); + times[j] = new; + idx++; + } + } + } + gts->avail_time_tables = 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; + + 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(>s->itime_table[t]); + if (ret) + return ret; + } + + for (g = 0; g < gts->num_hwgain; g++) { + ret = sanity_check_gain(>s->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, + >s->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; + *length = gts->num_avail_time_tables; + + 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"); |