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[97.64.17.87]) by smtp.gmail.com with ESMTPSA id v76sm50500957pfj.145.2018.12.05.06.10.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 05 Dec 2018 06:10:45 -0800 (PST) To: johan@kernel.org, gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org From: Song Qiang Subject: usb: thoughts of adding more support for FT232H Message-ID: <48bc71bb-68e4-8b29-f609-940c9aedc0a9@gmail.com> Date: Wed, 5 Dec 2018 22:10:40 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Johan, I've been developing some iio device drivers and found that some people would like to test their devices with a qemu system which requires an i2c or spi port on our development hosts. Usually this is achieved with a DLN-2 adapter, while this is a bit difficult for me because it costs ~175$ in my country. Then I found that FTDI's FT232H supports both these two modes and costs only less than 5$ but without full support in kernel. The ftdi-sio driver supports FT232H only as a serial converter. So I'm planning to write a mfd driver for it supports both these three modes, here are my thoughts:  - This device cannot support these three modes together because they    share some common pins, so I'm planning to add a sysfs entry    'current_mode' for selecting which mode the device should be working    on.  - This device is in uart mode on reset, so default mode would be reset,    too. This also helps for people only want to use this as a serial    converter feels nothing has happened (compatible).  - I was trying to reuse the ftdi-sio driver but it seems like mfd can    only register platform devices, while this is a usb driver. I may    have to copy some functions from this driver. Would you share any ideas? I'd appreciate it. yours, Song Qiang