Hi Ricardo, On Wed, May 23, 2018 at 11:17:20AM +0200, Ricardo Ribalda Delgado wrote: > Hi > > I have a flash controller connected to the main computer via a usb to > serial. My plan is to expose it to the system as a video4linux subdevice. > > With the inclusion of serdev I was expecting that it would be as easy as > adding a i2c device, but seems that there are some functionality that it is > still not implemented: > > 1) Serdev for usb serial devices. Right, I didn't want to enable serdev for USB serial before we have determined how to handle hotplugging (e.g. in serdev core or by making sure every serdev driver can handle devices going away at any time) in order to avoid having things crash left and right. I have out-of-tree code for USB serial that I use for testing purposes, so it's mostly a matter of finding the time to think this through. > 2) Instatiating via sysfs. Something like > echo hci_nokia > /sys/bus/serio/devices/serio0/new_device > (inspired in: echo eeprom 0x50 > /sys/bus/i2c/devices/i2c-3/new_device) Serdev currently only supports device tree and ACPI. Using out-of-tree code, you could load a device tree fragment during runtime to describe your serial bus (or you just amend the device tree). Using device tree overlays would have the benefit of being able to describe associated resources (e.g. reset gpios) which a simple compatible string (or equivalent) would not. But there are examples where a simple compatible string would do, for example an existing CEC device presenting itself as a generic USB CDC device (hopefully with a dedicated VID/PID so that no user-space configuration is needed at all). > 3) Support for probing: Like hwmon for i2c What would you probe for (since there is no generic protocol for serial devices)? > -Are these two things in the drawing board? > -if not, would it be something worth considering/reviewing for > upstream? So the first two points have been given some thought and is something we'd want to have eventually, while the third point has mostly been rejected (I think). Johan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
