Re: [PATCH v2 6/9] vfio/mdev: Add mdev available instance checking to the core

[Eric Farman <farman@linux.ibm.com>]

On Tue, 2021-09-21 at 10:19 -0300, Jason Gunthorpe wrote:
> On Mon, Sep 20, 2021 at 08:02:29PM +0200, Cornelia Huck wrote:
> > On Thu, Sep 09 2021, Jason Gunthorpe <jgg@nvidia.com> wrote:
> > 
> > > Many of the mdev drivers use a simple counter for keeping track
> > > of the
> > > available instances. Move this code to the core code and store
> > > the counter
> > > in the mdev_type. Implement it using correct locking, fixing
> > > mdpy.
> > > 
> > > Drivers provide a get_available() callback to set the number of
> > > available
> > > instances for their mtypes which is fixed at registration time.
> > > The core
> > > provides a standard sysfs attribute to return the
> > > available_instances.
> > 
> > So, according to the documentation, available_instances is
> > mandatory. This means that drivers either need to provide
> > get_available
> > or implement their own version of the attribute. I think we want to
> > update vfio-mediated-device.rst as well?
> 
> I added this, and something similar for the device_api patch too,
> thanks
> 
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> b/Documentation/driver-api/vfio-mediated-device.rst
> index 9f26079cacae35..0a130d76b33a48 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -106,6 +106,7 @@ structure to represent a mediated device's
> driver::
>  	     int  (*probe)  (struct mdev_device *dev);
>  	     void (*remove) (struct mdev_device *dev);
>  	     struct device_driver    driver;
> +	     unsigned int (*get_available)(struct mdev_type *mtype);
>       };
>  
>  A mediated bus driver for mdev should use this structure in the
> function calls
> @@ -230,7 +231,8 @@ Directories and files under the sysfs for Each
> Physical Device
>  * available_instances
>  
>    This attribute should show the number of devices of type <type-id> 
> that can be
> -  created.
> +  created. Drivers can supply a get_availble() function pointer to 

s/availble/available/

> have the core
> +  code create and maintain this sysfs automatically.
>  
>  * [device]
>