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    SubjectRE: RFC: (re-)binding the VFIO platform driver to a platform device
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    > -----Original Message-----
    > From: Wood Scott-B07421
    > Sent: Wednesday, October 09, 2013 2:22 PM
    > To: Yoder Stuart-B08248
    > Cc: Wood Scott-B07421; Kim Phillips; Christoffer Dall; Alex Williamson;
    > linux-kernel@vger.kernel.org; a.motakis@virtualopensystems.com;
    > agraf@suse.de; Sethi Varun-B16395; Bhushan Bharat-R65777;
    > peter.maydell@linaro.org; santosh.shukla@linaro.org; kvm@vger.kernel.org;
    > gregkh@linuxfoundation.org
    > Subject: Re: RFC: (re-)binding the VFIO platform driver to a platform
    > device
    >
    > On Wed, 2013-10-09 at 14:02 -0500, Yoder Stuart-B08248 wrote:
    > > Have been thinking about this issue some more. As Scott mentioned,
    > > 'wildcard' matching for a driver can be fairly done in the platform
    > > bus driver. We could add a new flag to the platform driver struct:
    > >
    > > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
    > > index 4f8bef3..4d6cf14 100644
    > > --- a/drivers/base/platform.c
    > > +++ b/drivers/base/platform.c
    > > @@ -727,6 +727,10 @@ static int platform_match(struct device *dev,
    > struct device_driver *drv)
    > > struct platform_device *pdev = to_platform_device(dev);
    > > struct platform_driver *pdrv = to_platform_driver(drv);
    > >
    > > + /* the driver matches any device */
    > > + if (pdrv->match_any)
    > > + return 1;
    > > +
    > > /* Attempt an OF style match first */
    > > if (of_driver_match_device(dev, drv))
    > > return 1;
    > >
    > > However, the more problematic issue is that a bus driver has no way to
    > > differentiate from an explicit bind request via sysfs and a bind that
    > > happened through bus probing.
    >
    > Again, I think the wildcard match should be orthogonal to "don't bind by
    > default" as far as the mechanism goes.
    >
    > There's already a "bool suppress_bind_attrs" to prevent sysfs
    > bind/unbind. I suggested a similar flag to mean the oppsosite -- bind
    > *only* through sysfs. Greg KH was skeptical and wanted to see a patch
    > before any further discussion.

    Ah, think I understand now...yes that works as well, and would be
    less intrustive. So are you writing a patch? :)

    It would be something like this, right?

    diff --git a/drivers/base/dd.c b/drivers/base/dd.c
    index 35fa368..c9a61ea 100644
    --- a/drivers/base/dd.c
    +++ b/drivers/base/dd.c
    @@ -389,7 +389,7 @@ static int __device_attach(struct device_driver *drv, void *data)
    {
    struct device *dev = data;

    - if (!driver_match_device(drv, dev))
    + if (!drv->explicit_bind_only && !driver_match_device(drv, dev))
    return 0;

    return driver_probe_device(drv, dev);
    @@ -450,7 +450,7 @@ static int __driver_attach(struct device *dev, void *data)
    * is an error.
    */

    - if (!driver_match_device(drv, dev))
    + if (!drv->explicit_bind_only && !driver_match_device(drv, dev))
    return 0;

    if (dev->parent) /* Needed for USB */
    diff --git a/include/linux/device.h b/include/linux/device.h
    index 2a9d6ed..f2be980 100644
    --- a/include/linux/device.h
    +++ b/include/linux/device.h
    @@ -236,6 +236,7 @@ struct device_driver {
    const char *mod_name; /* used for built-in modules */

    bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
    + bool explicit_bind_only; /* enables bind/unbind via sysfs only */

    const struct of_device_id *of_match_table;
    const struct acpi_device_id *acpi_match_table;


    Stuart


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