Hi Marek, > The PWM beeper volume can be controlled by adjusting the PWM duty cycle, expose volume setting via sysfs, so users can make the beeper quieter. > This patch adds sysfs attribute 'volume' in range 0..50000, i.e. from 0 to 50% in 1/1000th of percent steps, this resolution should be sufficient. > > The reason for 50000 cap on volume or PWM duty cycle is because duty cycle above 50% again reduces the loudness, the PWM wave form is inverted > wave form of the one for duty cycle below 50% and the beeper gets quieter the closer the setting is to 100% . Hence, 50% cap where the wave form yields the loudest result. > > Signed-off-by: Marek Vasut <marex@xxxxxxx> > --- > An alternative option would be to extend the userspace input ABI, e.g. by using SND_TONE top 16bits to encode the duty cycle in 0..50000 range, and bottom 16bit to encode the existing frequency in Hz . Since frequency in Hz is likely to be below some 25 kHz for audible bell, this fits in 16bits just fine. Thoughts ? I tend to not change existing user-space interfaces. I would prefer to have an additional event or using sysfs. >--- >NOTE: This uses approach similar to [1], except it is much simpler. > [1] https://patchwork.kernel.org/project/linux-input/cover/20230201152128.614439-1-manuel.traut@xxxxxx/ This one is more complex, because the mapping between duty cycle and volume is not linear. Probably it depends also on the used beeper hardware which values are doing a significant change in volume. Therefore the patchset introduced a mapping between volume levels and duty cycle times in the device-tree to allow user-space applications to control the beeper volume hardware independently. Regards Manuel
