On Wed, Dec 05, 2018 at 04:17:18PM +0100, Anatolij Gustschin wrote: > Hi, > > On Wed, 5 Dec 2018 22:10:40 +0800 > Song Qiang songqiang1304521@xxxxxxxxx wrote: > ... > >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: > > There already has been a discussion [1] about adding an MFD driver for > FT232H, since the operating modes are mutually exclusive (and bus pins > shared between different modes), the MFD approach doesn't seem to be > a good fit. > > > - 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. > > There is a patch series [2] adding an interface driver for FT232H- > based adapter devices, it already supports adding custom MPSSE based > SPI busses with SPI slaves for a custom USB PID. It already supports > adding custom CBUS-/MPSSE-GPIO adapters for user-defined USB PID. > Adding I2C driver/adapter support should be easy, too. Maybe you can > re-use it. > [1] https://patchwork.kernel.org/patch/9828985 > [2] https://patchwork.kernel.org/project/linux-usb/list/?series=48255 I was going to refer to these series, but Anatolij beat me to it (haven't looked at [2] myself yet, though). Thanks, Johan
