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Date:   Fri, 1 Jul 2022 09:16:17 +0200
From:   "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To:     Neal Liu <neal_liu@aspeedtech.com>
Cc:     "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>
Subject: Re: Questions about usb to serial driver
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On Fri, Jul 01, 2022 at 03:16:13AM +0000, Neal Liu wrote:
> Hi all,
> 
> I have a question about USB-serial and I hope I can find the answer from here.
> I'll be appreciated it if there is any feedback from you.
> 
> My question is If I have a USB device controller (udc) and a uart controller (16550) independently in a SoC,
> is there any usb-serial drivers or applications that could possible to support/connect:
> -	udc tx to uart rx
> -	uart tx to udc rx
> 
> Any chance I can make this SoC as a usb-serial devices?

Sure, use the CONFIG_USB_CONFIGFS_SERIAL or CONFIG_USB_CONFIGFS_ACM
build options and hook your gadget up to the serial port in userspace
and you will have a very expensive usb-serial converter (there are very
cheap chips that do the same thing if you want to make a simpler
device.)

hope this helps,

greg k-h