Hi, >On Mon 2019-07-22 13:56:44, Pavel Machek wrote: >> Hi! >> >> > > >> This patch introduce new Cadence USBSS DRD driver to linux kernel. >> > > >> >> > > >> The Cadence USBSS DRD Controller is a highly configurable IP Core which >> > > >> can be instantiated as Dual-Role Device (DRD), Peripheral Only and >> > > >> Host Only (XHCI)configurations. >> > > > >> > > >I see you are using debugfs to select between DRD, peripheral-onlyh and XHCI... >> > > > >> > > >Is that good idea? >> > > >> > > Yes driver allows selecting dr_mode by debugfs. Controller also support such functionality >> > > so I don't understand why would it not be a good idea. >> > > >> > > I personally use this for testing but it can be used to limit controller functionality without >> > > recompiling kernel. >> > >> > debugfs is ONLY for debugging, never rely on it being enabled, or >> > mounted, on a system in order to have any normal operation happen. >> > >> > So for testing, yes, this is fine. If this is going to be the normal >> > api/interface for how to control this driver, no, that is not acceptable >> > at all. >> >> It makes a lot of sense for end-user to toggle this... for example >> when he is lacking right cable for proper otg detection. As it is >> third driver offering this functionality, I believe we should stop >> treating it as debugging. > >At least renesas usb controller seems to have variables in sysfs: >drivers/phy/renesas/phy-rcar-gen3-usb2.c : functions role_show and >role_store. See also >Documentation/ABI/testing/sysfs-platform-phy-rcar-gen3-usb2 . > >I believe this driver should do same. > CDNS3 driver use the role framework and also has such variable defined in role switch framework. https://elixir.bootlin.com/linux/latest/source/drivers/usb/roles/class.c Regards, Pawel
