Hi Lars,

> 
> Unfortunately I must come back to this issue.
> I got hands on a few new EC21s here and guess what ?
> The mux order is back to the original one again. This means, the aux
> channel has to be the second channel.
> So I did a bit of investigation why and when this happened. But
> information is rare.
> The modems I originally worked on and created the patch for have
> Firmware EC21EFAR06A01M4G_BETA0318. (Reversed mux order)
> The new ones do have version EC21EFAR06A03M4G. (original mux order)
> I know that there was a version EC21EFAR02A02M4G that did not support
> cmux at all.
> Due to some Quectel Confidential Document in a firmware version
> "R02A03" some bug was fixed in cmux, so cmux must be in there since
> then.
> The EC21EFAR06A01M4G_BETA0318 that I have is dated inbetween
> EC21EFAR02A02M4G and this "R02A03".
> The mux order must have changed between EC21EFAR06A01M4G_BETA0318 and
> EC21EFAR06A03M4G.
> I suspect (without knowing for sure) due to the beta-nature of my
> firmware, that this is the only firmware with reversed mux order and
> that they changed it after that and "R02A03" up until
> EC21EFAR06A03M4G share the same original mux order. According to Quectel
> the EC21EFAR06A01M4G_BETA0318 firmware I have here is not "out in the
> wild". The modems I have here are the only ones with this firmware.
> 
> So my question is what's best to do now ?
> 
> I feel the best would be to revert this patch. I am very sorry for this.
> New modems will work and I suspect old modems "out in the wild" will
> work also. I don't care about supporting the few "BETA0318" modems I
> have here.

I guess just send a revert patch with the reasons outlined in the commit 
description and I can take it.

> 
> Another way would be to leave this patch and implement some firmware
> switch and use reversed mux order for the "BETA0318" only I have and use
> normal original mux order for all other cases.

That would also be fine.

Regards,
-Denis