linux-kernel - Re: [PATCH v9 3/6] pci:host: Add Altera PCIe host controller driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5210459.PtmhWaT6RM@wuerfel>
Date:	Wed, 14 Oct 2015 11:36:04 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Russell King <linux@....linux.org.uk>,
	Marc Zyngier <marc.zyngier@....com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH v9 3/6] pci:host: Add Altera PCIe host controller driver

On Wednesday 14 October 2015 17:28:45 Ley Foon Tan wrote:
> On Wed, Oct 14, 2015 at 5:09 PM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Wednesday 14 October 2015 16:32:25 Ley Foon Tan wrote:
> >> On Wed, Oct 14, 2015 at 4:20 PM, Arnd Bergmann <arnd@...db.de> wrote:
> >> > On Wednesday 14 October 2015 10:41:29 Ley Foon Tan wrote:
> >> >> +static int altera_pcie_remove(struct platform_device *pdev)
> >> >> +{
> >> >> +     struct altera_pcie *pcie = platform_get_drvdata(pdev);
> >> >> +
> >> >> +     altera_pcie_free_irq_domain(pcie);
> >> >> +     platform_set_drvdata(pdev, NULL);
> >> >> +     return 0;
> >> >> +}
> >> >
> >> > I just noticed this. Does it actually work to unload the module
> >> > and tear down all the pci_dev structures in a safe way?
> >> Good catch. It only can be compiled as builtin-moduley now, so we can
> >> remove this _remove callback function.
> >
> > I think we should change both: make it possible to load the
> > driver dynamically, and remove the altera_pcie_remove function.
> This driver depends on the pci fixups to work correctly. But, fixups
> callback functions in this driver are not being call if the driver is
> loadable module.

Ah, I see. We should find a better way to deal with this, as we
are getting an increasing number of host driver specific fixups.

Bjorn, do you have any idea here?

Could we perhaps have a helper function that lets us register
fixups dynamically?

> The linker script keeps all pci fixup callbacks in pci fixup regions
> during kernel compile time. So, it needs to be builtin module. Do you
> know any way we can update those fixup regions?

The only method I'm aware of at the moment is move the fixups to
drivers/pci/quirks.c and enclose them in an #ifdef if you want them
to not appear in kernels that don't support your SoC.

> > You can prevent the module from being unloaded if you also remove
> > the module_platform_driver() directive and add a module_init()
> > without a matching module_exit().
> >
> > Please also add a '.suppress_bind_attrs = true,' flag in the driver
> > struct to prevent manual unbinding.
> I think we don't need these if it only can work as builtin module.

No, this is orthogonal, you need it either way, as built-in drivers
can still be unbound by writing to sysfs. Try writing the device name
to /sys/bus/platform/drivers/altera-pcie/unbind and watch it blow up ;-)

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/