Hi Guenter, On Thu, 2 May 2024 at 23:52, Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > On 5/2/24 10:25, Naresh Solanki wrote: > [ ... ] > > >>> + u8 pwm[MAX6639_NDEV]; /* Register value: Duty cycle 0..120 */ > >> > >> pwm caching needs to be dropped as well. It is no longer initialized in > >> max6639_init_client(), but updated and later used in pwm_store() and > >> pwm_show(). Looking at the datasheet, the pwm registers are volatile > >> and should not be cached in the first place. > > Yes. I did that but found that the register is write only. i.e., > > Odd. The datasheet says that it is r/w or, rather, that reading it returns > the _current_ pwm value and writing it sets the target pwm value in pwm mode. > > What happens when the register is read ? Upon revisiting the datasheet and conducting further testing, it appears that my previous response was inaccurate. After testing, it's clear that it reads what is being written & hence it's perfectly fine to remove variable pwm[] from local caching. Verified using below command: ---- i2cset -f -y 130 0x2e 0x26 0x10; i2cget -f -y 130 0x2e 0x26 0x10 ---- Regards, Naresh > > Thanks, > Guenter >
