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. Thanks and best regards, Pavel -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
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