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SubjectRe: [PATCH v2] ide/macide: Convert Mac IDE driver to platform driver
On Tue, 15 Sep 2020, Geert Uytterhoeven wrote:

> > > > --- a/drivers/ide/macide.c
> > > > +++ b/drivers/ide/macide.c
> > >
> > > > @@ -109,42 +110,61 @@ static const char *mac_ide_name[] =
> > > > * Probe for a Macintosh IDE interface
> > > > */
> > > >
> > > > -static int __init macide_init(void)
> > > > +static int mac_ide_probe(struct platform_device *pdev)
> > > > {
> > >
> > > > printk(KERN_INFO "ide: Macintosh %s IDE controller\n",
> > > > mac_ide_name[macintosh_config->ide_type - 1]);
> > > >
> > > > - macide_setup_ports(&hw, base, irq);
> > > > + macide_setup_ports(&hw, mem->start, irq->start);
> > > >
> > > > - return ide_host_add(&d, hws, 1, NULL);
> > > > + rc = ide_host_add(&d, hws, 1, &host);
> > > > + if (rc)
> > > > + return rc;
> > > > +
> > > > + platform_set_drvdata(pdev, host);
> > >
> > > Move one up, to play it safe?
> > >
> >
> > You mean, before calling ide_host_add? The 'host' pointer is uninitialized
> > prior to that call.
>
> Oh right, so the IDE subsystem doesn't let you use the drvdata inside
> your driver (besides in remove()) in a safe way :-(
>

The IDE subsystem does allow other patterns here. I could have changed
ide_host_alloc() into ide_host_register() followed by ide_host_add() but I
could not see any benefit from that change.

A quick search for "platform_device" shows that the driver does not use
any uninitialized driver_data pointer (because ide_ifr is a global). In
your message of September 9th you readily reached the same conclusion when
you reviewed v1.

If mac_ide_probe() followed the usual pattern it might make review easier
(as reviewers may not wish to consider the entire driver) but does that
really make the code more "safe"?

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