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SubjectRe: [PATCH v2 1/1] s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem
On Mon, 18 Feb 2019 19:08:48 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> Libudev relies on having a subsystem link for non-root devices. To
> avoid libudev (and potentially other userspace tools) choking on the
> matrix device let us introduce a vfio_ap bus and with that the vfio_ap
> bus subsytem, and make the matrix device reside within it.
>
> Doing this we need to suppress the forced link from the matrix device to
> the vfio_ap driver and we suppress the device_type we do not need

s/suppress/remove/ ?

> anymore.
>
> Since the associated matrix driver is not the vfio_ap driver any more,
> we have to change the search for the devices on the vfio_ap driver in
> the function vfio_ap_verify_queue_reserved.
>
> Reported-by: Marc Hartmayer <mhartmay@linux.ibm.com>
> Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
> drivers/s390/crypto/vfio_ap_drv.c | 48 +++++++++++++++++++++++++++++------
> drivers/s390/crypto/vfio_ap_ops.c | 4 +--
> drivers/s390/crypto/vfio_ap_private.h | 1 +
> 3 files changed, 43 insertions(+), 10 deletions(-)

(...)

> @@ -62,6 +58,27 @@ static void vfio_ap_matrix_dev_release(struct device *dev)
> kfree(matrix_dev);
> }
>
> +static int matrix_bus_match(struct device *dev, struct device_driver *drv)
> +{
> + return 1;
> +}
> +
> +static struct bus_type matrix_bus = {
> + .name = "vfio_ap",
> + .match = &matrix_bus_match,
> +};
> +
> +static int matrix_probe(struct device *dev)
> +{
> + return 0;
> +}

I don't think you need this (the important function is the match
function of the bus).

> +
> +static struct device_driver matrix_driver = {
> + .name = "vfio_ap",
> + .bus = &matrix_bus,
> + .probe = matrix_probe,
> +};
> +
> static int vfio_ap_matrix_dev_create(void)
> {
> int ret;

It's a bit annoying that we need to introduce a bus that basically does
nothing, but I think this looks sane.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

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