netdev - RE: [PATCH 1/4] mdev: Introduce sha1 based mdev alias

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Date:   Tue, 27 Aug 2019 11:12:23 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Cornelia Huck <cohuck@...hat.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH 1/4] mdev: Introduce sha1 based mdev alias



> -----Original Message-----
> From: Cornelia Huck <cohuck@...hat.com>
> Sent: Tuesday, August 27, 2019 3:54 PM
> To: Parav Pandit <parav@...lanox.com>
> Cc: alex.williamson@...hat.com; Jiri Pirko <jiri@...lanox.com>;
> kwankhede@...dia.com; davem@...emloft.net; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; netdev@...r.kernel.org
> Subject: Re: [PATCH 1/4] mdev: Introduce sha1 based mdev alias
> 
> On Mon, 26 Aug 2019 15:41:16 -0500
> Parav Pandit <parav@...lanox.com> wrote:
> 
> > Whenever a parent requests to generate mdev alias, generate a mdev
> > alias.
> > It is an optional attribute that parent can request to generate for
> > each of its child mdev.
> > mdev alias is generated using sha1 from the mdev name.
> 
> Maybe add some motivation here as well?
> 
> "Some vendor drivers want an identifier for an mdev device that is shorter than
> the uuid, due to length restrictions in the consumers of that identifier.
> 
> Add a callback that allows a vendor driver to request an alias of a specified
> length to be generated (via sha1) for an mdev device. If generated, that alias is
> checked for collisions."
> 
I did described the motivation in the cover letter with example and this design discussion thread.
I will include above summary in v1.
 
> What about:
> 
> * @get_alias_length: optional callback to specify length of the alias to create
> *                    Returns unsigned integer: length of the alias to be created,
> *                                              0 to not create an alias
> 
Ack.

> I also think it might be beneficial to add a device parameter here now (rather
> than later); that seems to be something that makes sense.
> 
Without showing the use, it shouldn't be added.

> >   * Parent device that support mediated device should be registered with
> mdev
> >   * module with mdev_parent_ops structure.
> >   **/
> > @@ -92,6 +95,7 @@ struct mdev_parent_ops {
> >  	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> >  			 unsigned long arg);
> >  	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct
> *vma);
> > +	unsigned int (*get_alias_length)(void);
> >  };
> >
> >  /* interface for exporting mdev supported type attributes */