Re: [PATCH v4 1/9] driver core: add a faux bus for use when a simple device/bus is needed

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Feb 11, 2025 at 02:43:20AM -0500, Kurt Borja wrote:
> On Tue Feb 11, 2025 at 2:33 AM -05, Greg Kroah-Hartman wrote:
> > On Tue, Feb 11, 2025 at 08:27:26AM +0100, Greg Kroah-Hartman wrote:
> >> On Mon, Feb 10, 2025 at 12:56:46PM -0500, Kurt Borja wrote:
> >> I'll work on adding "if probe failed, don't let the device be created"
> >> logic as it's a simple change, BUT it is a functionally different change
> >> from what the current api that this code is replacing is doing (i.e. the
> >> current platform device creation code does this today and no one has
> >> ever hit this in their use of it in the past few decades.)
> >
> > How about something as simple as this change, does that provide what you
> > are thinking about here?  Only compile tested, not runtime tested at
> > all:
> 
> Yes, LGTM. However dev->driver is set to NULL if the probe fails so
> wouldn't
> 
> 	if (!dev->driver)
> 
> do the job?

True, that would work, and be much simpler, I'll go add that AND
actually test it :)

> I understand your point about groups. This of course solves it, although
> isn't there a small windows between device_add() and device_destroy() in
> the failed probe path, in which a show/store/visibility method could
> dereference a NULL drvdata?

Ok, I looked it up and it turns out that the groups wouldn't have even
been created if probe() failed (see the call to call_driver_probe() in
really_probe() in drivers/base/dd.c)  So all should be good here.

thanks,

greg k-h