On Wed, Jul 13, 2022 at 08:36:38PM +0300, Andy Shevchenko wrote: > On Wed, Jul 13, 2022 at 03:14:18PM +0200, Nuno Sá wrote: > > This change prepares the gpio core to look at firmware flags and set > > 'FLAG_BIAS_DISABLE' if necessary. It works in similar way to > > 'GPIO_PULL_DOWN' and 'GPIO_PULL_UP'. > > ... > > > GPIO_PULL_UP = (1 << 4), > > GPIO_PULL_DOWN = (1 << 5), > > + GPIO_PULL_DISABLE = (1 << 6), > > To me it seems superfluous. You have already two flags: > PUp > PDown > When none is set --> Pdisable > Agree with Andy on this. The FLAG_BIAS_DISABLE was added, by me, to allow the cdev interface to support bias. cdev requires a "don't care" state, distinct from an explicit BIAS_DISABLE. The FLAG_BIAS_DISABLE allows gpiolib-cdev to communicate that to gpiolib, without altering the interpretation of the existing PULL_UP and PULL_DOWN flags. That is not an issue on the machine interface, where the two GPIO_PULL flags suffice. If you are looking for the place where FLAG_BIAS_DISABLE is set it is in gpio_v2_line_config_flags_to_desc_flags() in gpiolib-cdev.c. Referring to gpio_set_bias(), the only place in gpiolib the FLAG_BIAS_DISABLE is used, if neither FLAG_PULL_UP, FLAG_PULL_DOWN, nor FLAG_BIAS_DISABLE are set then the bias configuration remains unchanged (the don't care case) - no change is passed to the driver. Otherwise the corresponding PIN_CONFIG_BIAS flag is passed to the driver. If there are cases of drivers not fully or correctly supporting those PIN_CONFIG_BIAS flags, then that is an issue with those drivers. Cheers, Kent.
