Re: git: 76bfa33f2598 - main - uart: Go back to returning '0' when we've probed the device.

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