Hi Pavel,
On 25 June 2018 at 20:18, Pavel Machek <pa...@ucw.cz> wrote:
> On Mon 2018-06-25 13:03:19, Baolin Wang wrote:
>> From: Bjorn Andersson <bjorn.anders...@linaro.org>
>>
>> Some LED controllers have support for autonomously controlling
>> brightness over time, according to some preprogrammed pattern or
>> function.
>>
>> This adds a new optional operator that LED class drivers can implement
>> if they support such functionality as well as a new device attribute to
>> configure the pattern for a given LED.
>
> Thanks for doing this!
>
>> index 5f67f7a..fe90a12 100644
>> --- a/Documentation/ABI/testing/sysfs-class-led
>> +++ b/Documentation/ABI/testing/sysfs-class-led
>> @@ -61,3 +61,19 @@ Description:
>> gpio and backlight triggers. In case of the backlight trigger,
>> it is useful when driving a LED which is intended to indicate
>> a device in a standby like state.
>> +
>> +What: /sys/class/leds/<led>/pattern
>> +Date: June 2018
>> +KernelVersion: 4.18
>> +Description:
>> + Specify a pattern for the LED, for LED hardware that support
>> + altering the brightness as a function of time.
>> +
>> + The pattern is given by a series of tuples, of brightness and
>> + duration (ms). The LED is expected to traverse the series and
>> + each brightness value for the specified duration.
>> +
>> + As LED hardware might have different capabilities and precision
>> + the requested pattern might be slighly adjusted by the driver
>> + and the resulting pattern of such operation should be returned
>> + when this file is read.
>
> I'd add "Duration of 0 means brightness should immediately change to
> new value."
Sure.
>
>> + struct led_classdev *led_cdev = dev_get_drvdata(dev);
>> + struct led_pattern *pattern = NULL;
>> + unsigned long val;
>> + char *sbegin;
>> + char *elem;
>> + char *s;
>> + int ret, len = 0;
>> + bool odd = true;
>> +
>> + s = sbegin = kstrndup(buf, size, GFP_KERNEL);
>> + if (!s)
>> + return -ENOMEM;
>> +
>> + /* Trim trailing newline */
>> + s[strcspn(s, "\n")] = '\0';
>
> Is substring function best to use here? Will it do the right thing
> when \n is not present?
We always have a '\n' to present the end of the string passed from
userspace. Or anything I missed here?
>
>> + /* If the remaining string is empty, clear the pattern */
>> + if (!s[0]) {
>> + ret = led_cdev->pattern_clear(led_cdev);
>> + goto out;
>> + }
>> +
>> + pattern = kcalloc(size, sizeof(*pattern), GFP_KERNEL);
>> + if (!pattern) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + /* Parse out the brightness & delta_t touples and check for repeat */
>> + while ((elem = strsep(&s, " ")) != NULL) {
>> + ret = kstrtoul(elem, 10, &val);
>> + if (ret)
>> + goto out;
>> +
>> + if (odd) {
>> + pattern[len].brightness = val;
>> + } else {
>> + /* Ensure we don't have any delta_t == 0 */
>> + if (!val) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>
> I believe we should support delta_t of 0 for "change immediately".
OK. Thanks for your comments.
--
Baolin Wang
Best Regards
