linux-kernel - Re: [PATCH v3 0/2] Add support for MaxLinear/Exar USB to serial converters

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Date:   Fri, 5 Jun 2020 13:13:55 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     mani@...nel.org
Cc:     johan@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        patong.mxl@...il.com
Subject: Re: [PATCH v3 0/2] Add support for MaxLinear/Exar USB to serial
 converters

Em Fri,  1 May 2020 00:19:22 +0530
mani@...nel.org escreveu:

> From: Manivannan Sadhasivam <mani@...nel.org>
> 
> Hello,
> 
> This series adds support for MaxLinear/Exar USB to serial converters.
> This driver only supports XR21V141X series but it can easily be extended
> to other series in future.
> 
> This driver is inspired from the initial one submitted by Patong Yang:
> 
> https://patchwork.kernel.org/patch/10543261/
> 
> While the initial driver was a custom tty USB driver exposing whole
> new serial interface ttyXRUSBn, this version is completely based on USB
> serial core thus exposing the interfaces as ttyUSBn. This will avoid
> the overhead of exposing a new USB serial interface which the userspace
> tools are unaware of.

Hmm... I guess you also need the enclosed patch, to ensure that cdc_acm
won't try to hijack it, when the Kernel is built with both drivers.

Thanks,
Mauro

[PATCH] usb: cdc-acm: ignore Exar XR21V141X when serial driver is
 built

The RTS/CTS line discipline for this device doesn't follow
the standard. So, in order to properly support TX, a separate
driver is needed.

Ensure that cdc_acm will ignore it during probe time, if the
Kernel is built with support for it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index ded8d93834ca..f87288834ded 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -1889,7 +1889,11 @@ static const struct usb_device_id acm_ids[] = {
 	.driver_info = IGNORE_DEVICE,
 	},
 #endif
-
+#if IS_ENABLED(CONFIG_USB_SERIAL_XR)
+	{ USB_DEVICE(0x04e2, 0x1410),   /* XR21V141X uses a different rts/cts discipline */
+	.driver_info = IGNORE_DEVICE,
+	},
+#endif
 	/*Samsung phone in firmware update mode */
 	{ USB_DEVICE(0x04e8, 0x685d),
 	.driver_info = IGNORE_DEVICE,