Date: Thu, 7 May 2020 13:11:32 +0000 (UTC) From: Andriy Gapon <avg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r360779 - head/sys/dev/gpio Message-ID: <202005071311.047DBWqO094461@repo.freebsd.org>
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Author: avg Date: Thu May 7 13:11:32 2020 New Revision: 360779 URL: https://svnweb.freebsd.org/changeset/base/360779 Log: gpioiic_attach: fix a NULL pointer crash on hints-based systems The attach method uses GPIO_GET_BUS() to get a "newbus" device that provides a pin. But on hints-based systems a GPIO controller driver might not be fully initialized yet and it does not know gpiobus hanging off it. Thus, GPIO_GET_BUS() cannot be called yet. The reason is that controller drivers typically create a child gpiobus using gpiobus_attach_bus() and that leads to the following call chain: gpiobus_attach_bus() -> gpiobus_attach() -> bus_generic_attach(gpiobus) -> gpioiic_attach(). So, gpioiic_attach() is called before gpiobus_attach_bus() returns. I observed this bug with nctgpio driver on amd64. I think that the problem was introduced in r355276. The fix is to avoid calling GPIO_GET_BUS() from the attach method. Instead, we know that on hints-based systems only the parent gpiobus can provide the pins. Nothing is changed for FDT-based systems. MFC after: 1 week Modified: head/sys/dev/gpio/gpioiic.c Modified: head/sys/dev/gpio/gpioiic.c ============================================================================== --- head/sys/dev/gpio/gpioiic.c Thu May 7 12:43:28 2020 (r360778) +++ head/sys/dev/gpio/gpioiic.c Thu May 7 13:11:32 2020 (r360779) @@ -303,10 +303,20 @@ gpioiic_attach(device_t dev) return (ENXIO); } - /* Say what we came up with for pin config. */ + /* + * Say what we came up with for pin config. + * NB: in the !FDT case the controller driver might not be set up enough + * for GPIO_GET_BUS() to work. Also, our parent is the only gpiobus + * that can provide our pins. + */ device_printf(dev, "SCL pin: %s:%d, SDA pin: %s:%d\n", +#ifdef FDT device_get_nameunit(GPIO_GET_BUS(sc->sclpin->dev)), sc->sclpin->pin, device_get_nameunit(GPIO_GET_BUS(sc->sdapin->dev)), sc->sdapin->pin); +#else + device_get_nameunit(device_get_parent(dev)), sc->sclpin->pin, + device_get_nameunit(device_get_parent(dev)), sc->sdapin->pin); +#endif /* Add the bitbang driver as our only child; it will add iicbus. */ device_add_child(sc->dev, "iicbb", -1);
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