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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 03/10] driver core: Flow the return code from ->probe() through to sysfs bind
Date: Tue, 8 Jun 2021 09:30:23 -0300	[thread overview]
Message-ID: <20210608123023.GA1002214@nvidia.com> (raw)
In-Reply-To: <YL8SdymSgn9HHRcw@kroah.com>

On Tue, Jun 08, 2021 at 08:47:19AM +0200, Greg Kroah-Hartman wrote:
> On Mon, Jun 07, 2021 at 09:55:45PM -0300, Jason Gunthorpe wrote:
> > Currently really_probe() returns 1 on success and 0 if the probe() call
> > fails. This return code arrangement is designed to be useful for
> > __device_attach_driver() which is walking the device list and trying every
> > driver. 0 means to keep trying.
> > 
> > However, it is not useful for the other places that call through to
> > really_probe() that do actually want to see the probe() return code.
> > 
> > For instance bind_store() would be better to return the actual error code
> > from the driver's probe method, not discarding it and returning -ENODEV.
> 
> Why does that matter?  Why does it need to know this?

Proper return code to userspace are important. Knowing why the driver
probe() fails is certainly helpful for debugging. Is there are reason
to hide them? I think this is an improvement for sysfs bind.

Why this series needs it is because mdev has fixed sys uAPI at this point
that requires carring the return code from device driver probe() to
a mdev sysfs function.

> > -static int really_probe(struct device *dev, struct device_driver *drv)
> > +enum {
> > +	/* Set on output if the -ERR has come from a probe() function */
> > +	PROBEF_DRV_FAILED = 1 << 0,
> > +};
> > +
> > +static int really_probe(struct device *dev, struct device_driver *drv,
> > +			unsigned int *flags)
> 
> Ugh, no, please no functions with random "flags" in them, that way lies
> madness and unmaintainable code for decades to come.

The alternative to this something like this:

static int really_probe(struct device *dev, struct device_driver *drv,
			int *probe_err)

And since we still need the 'do not probe defer' in next patches then
it would have to be this:

static int really_probe(struct device *dev, struct device_driver *drv,
			int *probe_err, bool allow_probe_defer)

And the two new arguments flowed up through several function call
sites.

Do you prefer one of these more?

For your other question PROBEF_ means 'probe flag'.

Jason

  reply	other threads:[~2021-06-08 12:30 UTC|newest]

Thread overview: 55+ 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
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 [this message]
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
2021-06-14 15:08 Allow mdev drivers to directly create the vfio_device (v2 / alternative) Christoph Hellwig
2021-06-14 15:08 ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Christoph Hellwig
2021-06-15  5:18   ` Greg Kroah-Hartman
2021-06-15  5:18     ` Greg Kroah-Hartman
2021-06-15 10:31   ` Cornelia Huck
2021-06-15 10:31     ` Cornelia Huck
2021-06-15 13:35 Allow mdev drivers to directly create the vfio_device (v3) Christoph Hellwig
2021-06-15 13:35 ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Christoph Hellwig
2021-06-17 14:22 Allow mdev drivers to directly create the vfio_device (v4) Christoph Hellwig
2021-06-17 14:22 ` [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind Christoph Hellwig

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