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

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Message-ID: <20200606122735.GB31973@Mani-XPS-13-9360>
Date:   Sat, 6 Jun 2020 17:57:35 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Mauro Carvalho Chehab <mchehab+huawei@...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

Hi Mauro,

On Fri, Jun 05, 2020 at 01:13:55PM +0200, Mauro Carvalho Chehab wrote:
> 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.
> 

Ah right. I will include this patch in next iteration. Many thanks!

Regards,
Mani

> 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,
>