diff options
Diffstat (limited to 'drivers/video/backlight/pwm_bl.c')
| -rw-r--r-- | drivers/video/backlight/pwm_bl.c | 83 |
1 files changed, 83 insertions, 0 deletions
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 44ac5bde4e9d..105f199a656d 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -147,7 +147,11 @@ static int pwm_backlight_parse_dt(struct device *dev, struct platform_pwm_backlight_data *data) { struct device_node *node = dev->of_node; + unsigned int num_levels = 0; + unsigned int levels_count; + unsigned int num_steps; struct property *prop; + unsigned int *table; int length; u32 value; int ret; @@ -167,6 +171,7 @@ static int pwm_backlight_parse_dt(struct device *dev, /* read brightness levels from DT property */ if (data->max_brightness > 0) { size_t size = sizeof(*data->levels) * data->max_brightness; + unsigned int i, j, n = 0; data->levels = devm_kzalloc(dev, size, GFP_KERNEL); if (!data->levels) @@ -184,6 +189,84 @@ static int pwm_backlight_parse_dt(struct device *dev, return ret; data->dft_brightness = value; + + /* + * This property is optional, if is set enables linear + * interpolation between each of the values of brightness levels + * and creates a new pre-computed table. + */ + of_property_read_u32(node, "num-interpolated-steps", + &num_steps); + + /* + * Make sure that there is at least two entries in the + * brightness-levels table, otherwise we can't interpolate + * between two points. + */ + if (num_steps) { + if (data->max_brightness < 2) { + dev_err(dev, "can't interpolate\n"); + return -EINVAL; + } + + /* + * Recalculate the number of brightness levels, now + * taking in consideration the number of interpolated + * steps between two levels. + */ + for (i = 0; i < data->max_brightness - 1; i++) { + if ((data->levels[i + 1] - data->levels[i]) / + num_steps) + num_levels += num_steps; + else + num_levels++; + } + num_levels++; + dev_dbg(dev, "new number of brightness levels: %d\n", + num_levels); + + /* + * Create a new table of brightness levels with all the + * interpolated steps. + */ + size = sizeof(*table) * num_levels; + table = devm_kzalloc(dev, size, GFP_KERNEL); + if (!table) + return -ENOMEM; + + /* Fill the interpolated table. */ + levels_count = 0; + for (i = 0; i < data->max_brightness - 1; i++) { + value = data->levels[i]; + n = (data->levels[i + 1] - value) / num_steps; + if (n > 0) { + for (j = 0; j < num_steps; j++) { + table[levels_count] = value; + value += n; + levels_count++; + } + } else { + table[levels_count] = data->levels[i]; + levels_count++; + } + } + table[levels_count] = data->levels[i]; + + /* + * As we use interpolation lets remove current + * brightness levels table and replace for the + * new interpolated table. + */ + devm_kfree(dev, data->levels); + data->levels = table; + + /* + * Reassign max_brightness value to the new total number + * of brightness levels. + */ + data->max_brightness = num_levels; + } + data->max_brightness--; } |