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Subject: Re: [PATCH V2 3/5] vDPA: introduce vDPA bus
To:     Jason Gunthorpe <jgg@mellanox.com>
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References: <20200210035608.10002-1-jasowang@redhat.com>
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 <20200211134746.GI4271@mellanox.com>
 <cf7abcc9-f8ef-1fe2-248e-9b9028788ade@redhat.com>
 <20200212125108.GS4271@mellanox.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <12775659-1589-39e4-e344-b7a2c792b0f3@redhat.com>
Date:   Thu, 13 Feb 2020 11:34:10 +0800
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On 2020/2/12 =E4=B8=8B=E5=8D=888:51, Jason Gunthorpe wrote:
> On Wed, Feb 12, 2020 at 03:55:31PM +0800, Jason Wang wrote:
>>> The ida_simple_remove should probably be part of the class release
>>> function to make everything work right
>> It looks to me bus instead of class is the correct abstraction here si=
nce
>> the devices share a set of programming interface but not the semantics=
.
> device_release() doesn't call the bus release?


What it did is:

 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (dev->release)
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 dev->release(dev);
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 else if (dev->type && dev->ty=
pe->release)
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 dev->type->release(dev);
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 else if (dev->class && dev->c=
lass->dev_release)
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 dev->class->dev_release(dev);
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 else
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 WARN(1, KERN_ERR "Device '%s' does not have a release(=
)=20
function, it is broken and must be fixed. See Documentation/kobject.txt.\=
n",
 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dev_na=
me(dev));

So it looks not.


>   You have dev, type or
> class to choose from. Type is rarely used and doesn't seem to be used
> by vdpa, so class seems the right choice
>
> Jason


Yes, but my understanding is class and bus are mutually exclusive. So we=20
can't add a class to a device which is already attached on a bus.

Thanks