linux-kernel - Re: [RFC 3/3] PCI: tegra: Support driver unbinding

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Date:	Thu, 15 Aug 2013 12:34:52 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thierry Reding <treding@...dia.com>
Subject: Re: [RFC 3/3] PCI: tegra: Support driver unbinding

On Wed, Aug 14, 2013 at 03:43:40PM -0600, Stephen Warren wrote:
> On 08/13/2013 05:12 AM, Thierry Reding wrote:
> > Implement the platform driver's .remove() callback to free all resources
> > allocated during driver setup and call pci_common_exit() to cleanup ARM
> > specific datastructures. Unmap the fixed PCI I/O mapping by calling the
> > new pci_iounmap_io() function in the new .teardown() callback.
> > 
> > Finally, no longer set the .suppress_bind_attrs field to true to allow
> > the driver to unbind from a device.
> 
> > +static int tegra_pcie_remove(struct platform_device *pdev)
> > +{
> > +	struct tegra_pcie *pcie = platform_get_drvdata(pdev);
> > +	struct tegra_pcie_bus *bus, *tmp;
> > +	int err;
> > +
> > +	pci_common_exit(&pcie->sys);
> > +
> > +	list_for_each_entry_safe(bus, tmp, &pcie->busses, list) {
> > +		vunmap(bus->area->addr);
> > +		kfree(bus);
> > +	}
> > +
> > +	if (IS_ENABLED(CONFIG_PCI_MSI)) {
> > +		err = tegra_pcie_disable_msi(pcie);
> > +		if (err < 0)
> > +			return err;
> > +	}
> 
> Wouldn't it make sense to do that as early as possible in the function,
> to make sure that no MSI accidentally fires after some of the cleanup
> has already happened?

I don't think that's strictly necessary in this case. After the call to
pci_common_exit() there are no PCI devices left, there's not even a bus
left. All MSI users should have cleaned up after themselves.

Given that I thought it more useful to mirror the setup done in .probe()
to make it clearer what's being undone (and potentially what's missing).

Thierry

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