On Sun, May 17, 2020 at 11:56:08PM +0200, Heiko Stuebner wrote: > From: Heiko Stuebner <heiko.stuebner@xxxxxxxxxxxxxxxxxxxxx> > > The RE signal is used to control the duplex mode of transmissions, > aka receiving data while sending in full duplex mode, while stopping > receiving data in half-duplex mode. > > On a number of boards the !RE signal is tied to ground so reception > is always enabled except if the UART allows disabling the receiver. > This can be taken advantage of to implement half-duplex mode - like > done on 8250_bcm2835aux. > > Another solution is to tie !RE to RTS always forcing half-duplex mode. > > And finally there is the option to control the RE signal separately, > like done here by introducing a new rs485-specific gpio that can be > set depending on the RX_DURING_TX setting in the common em485 callbacks. ... > + port->rs485_re_gpio = devm_gpiod_get_optional(dev, "rs485-rx-enable", > + GPIOD_OUT_HIGH); While reviewing some other patch I realized that people are missing the point of these GPIO flags when pin is declared to be output. HIGH here means "asserted" (consider active-high vs. active-low in general). Is that the intention here? Lukas, same question to your patch. -- With Best Regards, Andy Shevchenko
