On Wed, Nov 27, 2019 at 11:17:51AM +0800, Je Yen Tam wrote: > This reverts commit fdc2de87124f5183a98ea7eced1f76dbdba22951 which is > commit 225607f75454 ("serial/8250: Add support for NI-Serial PXI/PXIe+485 devices"). That sentance does not make sense. fdc2de87124f ("serial/8250: Add support for NI-Serial PXI/PXIe+485 devices") is in the 5.4 kernel tree, where did the commit id "225607f75454" come from? I don't see it anywhere in Linus's tree. > The upstream introduced a breakage on NI-Serial PXI(e)-RS485 devices, > RS-232 variants have no issue. The Linux system can enumerate the Serial > PXI(e)-RS485 devices, but it broke the R/W operation on the ports. I can not parse this paragraph either, what do you mean by "The upstream"? > However, the implementation is working on the NI internal Linux RT kernel > but it does not work in the Linux main tree kernel. This is only affecting > NI products, specifically the RS-485 variants. Reverting the upstream > until a proper implementation that can apply to both NI internal Linux > kernel and Linux mainline kernel is figured out. So this patch really does not work at all? Can't you just find a simple fix to go on top of it to resolve the issue? You really want it all ripped out for 5.5 and 5.4.y? thanks, greg k-h