From: Dave Carey Date: Fri, 15 May 2026 14:19:40 +0000 (-0400) Subject: USB: cdc-acm: start bulk-IN polling when ALWAYS_POLL_CTRL is set X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5ab27ddd74e2d67a94c51c6f2ad87b1ff13912b;p=thirdparty%2Fkernel%2Fstable.git USB: cdc-acm: start bulk-IN polling when ALWAYS_POLL_CTRL is set The INGENIC 17EF:6161 touchscreen composite device has a ~55-second watchdog that resets the USB device if the bulk-IN endpoint on the CDC data interface goes unread. The existing ALWAYS_POLL_CTRL quirk keeps the notification endpoint (ctrlurb / EP 0x82) polling continuously, but that alone is insufficient: the firmware monitors bulk-IN activity, not just notification-endpoint activity. Add acm_submit_read_urbs() calls to the two ALWAYS_POLL_CTRL paths that already restart the ctrlurb: 1. acm_probe(): start bulk reads at probe time alongside the ctrlurb, so the watchdog is satisfied from first bind without requiring a userspace process to open /dev/ttyACMn. 2. acm_port_shutdown(): restart bulk reads after port close alongside the ctrlurb restart, so the watchdog keeps running when the last TTY user closes the port. acm_read_bulk_callback() already resubmits each URB unconditionally on normal completion, so once submitted the reads remain active until an explicit kill (disconnect, suspend). acm_submit_read_urb() is a no-op for URBs that are already in flight (read_urbs_free bit clear), so the existing acm_port_activate() call remains correct and races are avoided. Tested on Lenovo Yoga Book 9 14IAH10 (83KJ): without this patch the device resets every ~55 s when no TTY is open; with it the device remains stable indefinitely. Signed-off-by: Dave Carey Link: https://patch.msgid.link/20260515141940.751397-1-carvsdriver@gmail.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 54059e4fc6ed..0c6cdf553206 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -799,6 +799,9 @@ static void acm_port_shutdown(struct tty_port *port) "ctrl polling restart failed after port close\n"); /* port_shutdown() cleared DTR/RTS; restore them */ acm_set_control(acm, USB_CDC_CTRL_DTR | USB_CDC_CTRL_RTS); + if (acm_submit_read_urbs(acm, GFP_KERNEL)) + dev_dbg(&acm->control->dev, + "read urb restart failed after port close\n"); } } @@ -1566,6 +1569,9 @@ skip_countries: if (usb_submit_urb(acm->ctrlurb, GFP_KERNEL)) dev_warn(&intf->dev, "failed to start persistent ctrl polling\n"); + if (acm_submit_read_urbs(acm, GFP_KERNEL)) + dev_warn(&intf->dev, + "failed to start persistent bulk read polling\n"); } return 0;