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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). Changes since v2: - patch 2/2: lower the override notice from dev_info() to dev_dbg() so the driver stays quiet in normal operation (Greg Kroah-Hartman). Changes since v1: - Dropped the urb_defer_timer_ns and low_latency_defer_ns module-parameter patches, which addressed DMA-channel starvation on a host controller that does not enforce DMA-channel fairness. As Greg Kroah-Hartman noted, that belongs in the host controller driver, not as a per-driver workaround in ftdi_sio. - Dropped the per-port low_latency sysfs attribute and its serialisation fix, which depended on the hrtimer infrastructure introduced by the dropped patch and have no standalone purpose without it. Earlier postings: [v1] https://lore.kernel.org/linux-usb/cover.1781744946.git.naveen.reddy@ftdichip.com/ [v2] https://lore.kernel.org/linux-usb/cover.1782121274.git.naveen.reddy@ftdichip.com/ 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