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Patches 1 and 6 used module parameters (urb_defer_timer_ns and low_latency_defer_ns) to address DMA-channel starvation on a host controller that does not enforce DMA-channel fairness. Greg correctly pointed out that the host controller driver is the right place to fix that, and that ftdi_sio should not carry per-driver workarounds for an out-of-tree host controller deficiency. Those patches are dropped. Patches 4 and 5 (per-port low_latency sysfs attribute and its serialisation fix) depended on the hrtimer infrastructure introduced by the dropped patch 1 and have no standalone purpose without it. They are dropped too. This v2 contains only the two patches that are independent correctness fixes for ftdi_sio itself: 1. Retry transient errors (-ETIMEDOUT / -EPIPE / -EPROTO) on chip-side control transfers so that a single transient USB hiccup under bus load does not fail an otherwise-healthy one-shot configuration (e.g. a latency_timer sysfs write) back to userspace as -EIO. 2. Make an explicit sysfs write to latency_timer authoritative so that a userspace write is not silently clamped to 1 by the ASYNC_LOW_LATENCY tty flag left set by an earlier TIOCSSERIAL (setserial(8), libftdi, certain tcsetattr paths). Chinna Mopurigari Naveen Kumar Reddy (2): USB: serial: ftdi_sio: retry transient errors on chip-side control transfers USB: serial: ftdi_sio: make explicit latency_timer sysfs write authoritative drivers/usb/serial/ftdi_sio.c | 65 +++++++++++++++++++++++++++++++---- 1 file changed, 58 insertions(+), 7 deletions(-) base-commit: ba3e43a9e601636f5edb54e259a74f96ca3b8fd8 -- 2.43.0