Hi Grant, > I'm thinking that there is a very small window between reading > a register, modifying some bits and writing it back out, where > another process also does it. Say SMP and one CPU update fan_div1 > while other update fan_div2 -- adm1026 has eight of these over > two bytes to potentially interfere with each other. Correct, you convinced me. > But if the update request event stream is serialised by sysfs > or elsewhere on its way to the driver then there is no problem. No, it isn't. > If the i2c bus driver rate limits write traffic to bus, then > again there is no issue. I simply do not know. I ask to learn. The bus driver doesn't limit the traffic, it only makes sure that no more than one transfer happens at any given time. This alone doesn't cover the case above, as register modifications consists in two separate messages, and another message can slip inbetween. Thanks, -- Jean Delvare
