Date: Tue, 15 Oct 2024 11:32:40 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Warner Losh <imp@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: 76bfa33f2598 - main - uart: Go back to returning '0' when we've probed the device. Message-ID: <a35f8036-61e7-4b81-a4a3-6f1c693fedc0@FreeBSD.org> In-Reply-To: <202410151101.49FB1HA5077421@gitrepo.freebsd.org> References: <202410151101.49FB1HA5077421@gitrepo.freebsd.org>
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On 10/15/24 04:01, Warner Losh wrote: > The branch main has been updated by imp: > > URL: https://cgit.FreeBSD.org/src/commit/?id=76bfa33f259891a8b9108e20141bd18e2c8d312f > > commit 76bfa33f259891a8b9108e20141bd18e2c8d312f > Author: Warner Losh <imp@FreeBSD.org> > AuthorDate: 2024-10-15 10:59:29 +0000 > Commit: Warner Losh <imp@FreeBSD.org> > CommitDate: 2024-10-15 10:59:29 +0000 > > uart: Go back to returning '0' when we've probed the device. > > Two reasons for this: we know it's a uart after we call probe and it > returns successfully. Second, uart passes data between probe and attach > with softc. As it is now, we call probe twice, once in the bidding > process and once after bidding id done. However, the probe process for > uart isn't completely idempotent (we change state of the uart > sometimes). The second call can result in odd behavior (though so far > only in buggy version of other code I've not committed). The bigger > problem is the softc: newbus creates it, we populate it, then frees it > when we don't return 0 to claim the device. It then calls us again, we > repopulate it, and this time it doesn't free it before calling attach. > Returning 0 avoids both of these issues. The justification for doing it > in the commit that changed it was 'while I'm here', so there doesn't > seem to be a use case for it. Hmm, I think it was changed in this commit which wasn't a "while I'm here": commit b923a71020ae338f723d9aa01b5365c90aae2fec Author: Marcel Moolenaar <marcel@FreeBSD.org> Date: Fri Oct 28 06:30:39 2005 +0000 In uart_bus_probe() return BUS_PROBE_DEFAULT when the probe is successful. Notes: svn path=/head/; revision=151792 diff --git a/sys/dev/uart/uart_core.c b/sys/dev/uart/uart_core.c index 7b068187e565..b2ff203d0b2a 100644 --- a/sys/dev/uart/uart_core.c +++ b/sys/dev/uart/uart_core.c @@ -282,7 +282,7 @@ uart_bus_probe(device_t dev, int regshft, int rclk, int rid, int chan) error = UART_PROBE(sc); bus_release_resource(dev, sc->sc_rtype, sc->sc_rrid, sc->sc_rres); - return (error); + return ((error) ? error : BUS_PROBE_DEFAULT); } int It really is a bug to be depending on passing softc state from probe to attach and it would be ideal to fix that, but going back to returning 0 is ok for now. Maybe instead of '0' though use BUS_PROBE_SPECIFIC? -- John Baldwin
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