// SPDX-License-Identifier: GPL-2.0-only /* gain-time-scale conversion helpers for IIO light sensors * * Copyright (c) 2023 Matti Vaittinen */ #include #include #include #include #include #include #include #include #include #include #include #include /** * 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; if (scale > full || !scale) return -EINVAL; return div64_u64(full, scale); } /** * 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 i, j, new_idx, time_idx, ret = 0; 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-- > 0) { 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; for (i = 0; i < gts->num_itime; i++) kfree(per_time_gains[i]); kfree(per_time_gains); gts->per_time_avail_scale_tables = per_time_scales; return 0; err_free_out: for (i--; i >= 0; 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 (idx == 0 || times[idx - 1] < new) { times[idx++] = new; continue; } for (j = 0; j < idx; j++) { if (times[j] == new) break; if (times[j] > new) { memmove(×[j + 1], ×[j], (idx - j) * sizeof(int)); times[j] = new; idx++; break; } } } /* 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(>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_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 "); MODULE_DESCRIPTION("IIO light sensor gain-time-scale helpers");