On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote: > This patch adds generic support for serial multipoint > addressing. Two new ioctls are added. TIOCSADDR is used to Nit: "This patch adds..." is superfluous. Just write "Add ..." in imperative mood. > This change is necessary for supporting devices with RS485 > multipoint addressing [*]. If this is only used with RS485, why can't we just store the addresses in struct serial_rs485 and use the existing TIOCSRS485 and TIOCGRS485 ioctls? There's 20 bytes of padding left in struct serial_rs485 which you could use. No need to add more user-space ABI. > [*] Technically, RS485 is just an electronic spec and does not > itself specify the 9th bit addressing mode but 9th bit seems > at least "semi-standard" way to do addressing with RS485. Is 9th bit addressing actually used by an Intel customer or was it implemented just for feature completeness? I think this mode isn't used often (I've never seen a use case myself), primarily because it requires disabling parity. Thanks, Lukas
