diff options
| author | Marc Zyngier <maz@kernel.org> | 2026-03-01 12:44:40 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-11 16:17:55 +0100 |
| commit | 14ae24cba291bddfdc296bbcbfd00cd09d0498ef (patch) | |
| tree | 523ae8f49388dd46bf6effd599817f2d80451a3d | |
| parent | 8479891d1f04a8ce55366fe4ca361ccdb96f02e1 (diff) | |
usb: cdc-acm: Restore CAP_BRK functionnality to CH343
The CH343 USB/serial adapter is as buggy as it is popular (very).
One of its quirks is that despite being capable of signalling a
BREAK condition, it doesn't advertise it.
This used to work nonetheless until 66aad7d8d3ec5 ("usb: cdc-acm:
return correct error code on unsupported break") applied some
reasonable restrictions, preventing breaks from being emitted on
devices that do not advertise CAP_BRK.
Add a quirk for this particular device, so that breaks can still
be produced on some of my machines attached to my console server.
Fixes: 66aad7d8d3ec5 ("usb: cdc-acm: return correct error code on unsupported break")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable <stable@kernel.org>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Link: https://patch.msgid.link/20260301124440.1192752-1-maz@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/class/cdc-acm.c | 5 | ||||
| -rw-r--r-- | drivers/usb/class/cdc-acm.h | 1 |
2 files changed, 6 insertions, 0 deletions
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index ad38c746270a..7ede29d4c7c1 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1379,6 +1379,8 @@ made_compressed_probe: acm->ctrl_caps = h.usb_cdc_acm_descriptor->bmCapabilities; if (quirks & NO_CAP_LINE) acm->ctrl_caps &= ~USB_CDC_CAP_LINE; + if (quirks & MISSING_CAP_BRK) + acm->ctrl_caps |= USB_CDC_CAP_BRK; acm->ctrlsize = ctrlsize; acm->readsize = readsize; acm->rx_buflimit = num_rx_buf; @@ -2002,6 +2004,9 @@ static const struct usb_device_id acm_ids[] = { .driver_info = IGNORE_DEVICE, }, + /* CH343 supports CAP_BRK, but doesn't advertise it */ + { USB_DEVICE(0x1a86, 0x55d3), .driver_info = MISSING_CAP_BRK, }, + /* control interfaces without any protocol set */ { USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_ACM, USB_CDC_PROTO_NONE) }, diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h index 759ac15631d3..76f73853a60b 100644 --- a/drivers/usb/class/cdc-acm.h +++ b/drivers/usb/class/cdc-acm.h @@ -113,3 +113,4 @@ struct acm { #define CLEAR_HALT_CONDITIONS BIT(5) #define SEND_ZERO_PACKET BIT(6) #define DISABLE_ECHO BIT(7) +#define MISSING_CAP_BRK BIT(8) |