On Wed, 9 Mar 2022, Lukas Wunner wrote:

On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote:

quoted

On Sun, 6 Mar 2022, Lukas Wunner wrote:

quoted

On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote:

quoted

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.

It could if it is agreed that serial multipoint addressing is just
a thing in RS-485 and nowhere else? In that case, there is no point
in adding more generic support for it.

It's just that the above-quoted sentence in the commit message
specifically mentions RS485.

That sentence is just to justify why addressing mode is needed,
not to take a stance on whether it is only used with RS485 or not.

If you intend to use it with RS232
as well, that should be made explicit, otherwise one wonders why
it wasn't integrated into struct serial_rs485.

I have no idea how common 9th bit addressing mode is with RS232.
Goggle turns up links saying it's mainly used with RS485, "but also
RS232".  Since RS232 isn't a bus but a point-to-point link,
9th bit addressing doesn't seem to make as much sense.

While I don't know any better, I can image though that with an 
RS232-to-RS485 converter, it could make some sense.

If I put them back to serial_rs485 / rs485 config, it's basically just 
where I initially started from with this patchset (offlist).


-- 
 i.