On 21.02.19 18:17, Martin Kepplinger wrote:

This extends the user interface for rs485 communication:

We add a new flag, SER_RS485_DELAY_IN_USEC, to struct serial_rs485 that
indicates that delay_rts_before_send and delay_rts_after_send values are
interpreted in microsecond units.

Up until now, the code comment defined these values to hold the delays in
millisecond units. Especially with fast data rates (1Mbaut or more) that
are not too uncommon for RS485, 1ms become quite long. Users need to be
able to set shorter delays than 1 ms in order not to slow down the channel
unnecessarily.

So when delays are needed, but not as long as 1ms, this enables faster
communication channels without changing the baudrate.

Signed-off-by: Martin Kepplinger <redacted>
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revision history
----------------
v2: re-send as a proper series after fixing my mailserver
v1: initial implementation idea


So have this totally quirky patch that uses udelay() in our tree
for a looong time now because of the above reasons - and because we are lazy.
This is an attempt to get rid of said patch on our side and fix this properly.

What do you thing about adding a flag in general?

The following patches should integrate this idea in devicetree and drivers.
These changes are NOT tested on hardware but should behave predictably
enough. I use the delays in a driver that doesn't implement them yet at
all. I'll do that after this (or something similar) is merged - it's a 2-liner
then.

Also, a patch to the rs485conf tool, that is sometimes used instead of
ioctl() directly, will be prepared as well.

any objections of questions about having microsecond delays and this
series of changes?

thanks

                           martin