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From: Jason Gunthorpe <jgg@nvidia.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: kvm@vger.kernel.org, "Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH 01/10] driver core: Do not continue searching for drivers if deferred probe is used
Date: Tue, 8 Jun 2021 10:53:31 -0300	[thread overview]
Message-ID: <20210608135331.GH1002214@nvidia.com> (raw)
In-Reply-To: <YL9tAdxK+RMhwPFi@kroah.com>

On Tue, Jun 08, 2021 at 03:13:37PM +0200, Greg Kroah-Hartman wrote:

> > If multiple drivers are matchable what creates determinism in which
> > will bind?
> 
> Magic :)

I suppose you mean something like this code:

        /* Probe the USB device with the driver in hand, but only
         * defer to a generic driver in case the current USB
         * device driver has an id_table or a match function; i.e.,
         * when the device driver was explicitly matched against
         * a device.
         *
         * If the device driver does not have either of these,
         * then we assume that it can bind to any device and is
         * not truly a more specialized/non-generic driver, so a
         * return value of -ENODEV should not force the device
         * to be handled by the generic USB driver, as there
         * can still be another, more specialized, device driver.
         *
         * This accommodates the usbip driver.
         *
         * TODO: What if, in the future, there are multiple
         * specialized USB device drivers for a particular device?
         * In such cases, there is a need to try all matching
         * specialised device drivers prior to setting the
         * use_generic_driver bit.
         */
        error = udriver->probe(udev);
        if (error == -ENODEV && udriver != &usb_generic_driver &&
            (udriver->id_table || udriver->match)) {
                udev->use_generic_driver = 1;
                return -EPROBE_DEFER;
        }

So it does use EPROBE_DEFER to recycle through another attempt at
driver binding. Yikes. Why didn't it return -ENODEV I wonder?

But OK, I can think of no way to find all the cases like this to even
try to do something else at this point, so this has to be
preserved. I'll try to do that, maybe add a comment or two.

Jason

  reply	other threads:[~2021-06-08 13:53 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-08  0:55 [PATCH 00/10] Allow mdev drivers to directly create the vfio_device Jason Gunthorpe
2021-06-08  0:55 ` [Intel-gfx] " Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 01/10] driver core: Do not continue searching for drivers if deferred probe is used Jason Gunthorpe
2021-06-08  5:51   ` Christoph Hellwig
2021-06-08  6:44   ` Greg Kroah-Hartman
2021-06-08 12:16     ` Jason Gunthorpe
2021-06-08 13:13       ` Greg Kroah-Hartman
2021-06-08 13:53         ` Jason Gunthorpe [this message]
2021-06-08  7:35   ` Greg Kroah-Hartman
2021-06-08 12:17     ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 02/10] driver core: Pull required checks into driver_probe_device() Jason Gunthorpe
2021-06-08  5:59   ` Christoph Hellwig
2021-06-08 12:21     ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Jason Gunthorpe
2021-06-08  6:07   ` Christoph Hellwig
2021-06-08 23:53     ` Jason Gunthorpe
2021-06-08  6:47   ` Greg Kroah-Hartman
2021-06-08 12:30     ` Jason Gunthorpe
2021-06-08 13:16       ` Greg Kroah-Hartman
2021-06-08 14:03         ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 04/10] driver core: Don't return EPROBE_DEFER to userspace during " Jason Gunthorpe
2021-06-08  6:14   ` Christoph Hellwig
2021-06-08  7:37   ` Greg Kroah-Hartman
2021-06-08  0:55 ` [PATCH 05/10] driver core: Export device_driver_attach() Jason Gunthorpe
2021-06-08  6:19   ` Christoph Hellwig
2021-06-08 12:33     ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 06/10] vfio/mdev: Remove CONFIG_VFIO_MDEV_DEVICE Jason Gunthorpe
2021-06-08  0:55   ` [Intel-gfx] " Jason Gunthorpe
2021-06-08  6:20   ` Christoph Hellwig
2021-06-08  6:20     ` [Intel-gfx] " Christoph Hellwig
2021-06-11 12:40   ` Cornelia Huck
2021-06-11 12:40     ` [Intel-gfx] " Cornelia Huck
2021-06-14 12:35     ` Jason Gunthorpe
2021-06-14 12:35       ` [Intel-gfx] " Jason Gunthorpe
2021-06-14 12:35       ` Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 07/10] vfio/mdev: Allow the mdev_parent_ops to specify the device driver to bind Jason Gunthorpe
2021-06-08  6:21   ` Christoph Hellwig
2021-06-08  0:55 ` [PATCH 08/10] vfio/mtty: Convert to use vfio_register_group_dev() Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 09/10] vfio/mdpy: " Jason Gunthorpe
2021-06-08  0:55 ` [PATCH 10/10] vfio/mbochs: " Jason Gunthorpe
2021-06-08  6:22 ` [PATCH 00/10] Allow mdev drivers to directly create the vfio_device Christoph Hellwig
2021-06-08  6:22   ` [Intel-gfx] " Christoph Hellwig
2021-06-14 14:34 ` Kirti Wankhede
2021-06-14 14:34   ` [Intel-gfx] " Kirti Wankhede
2021-06-14 14:34   ` Kirti Wankhede
2021-06-14 14:36   ` Jason Gunthorpe
2021-06-14 14:36     ` [Intel-gfx] " Jason Gunthorpe
2021-06-14 14:36     ` Jason Gunthorpe

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