Re: [PATCH V5 2/6] modpost: add support for mdev class id

[Jason Wang]

On 2019/10/25 äå3:54, Alex Williamson wrote:
> On Thu, 24 Oct 2019 11:31:04 +0800
> Jason Wang <jasowang@xxxxxxxxxx> wrote:
>
> > On 2019/10/24 äå5:42, Alex Williamson wrote:
> > > On Wed, 23 Oct 2019 21:07:48 +0800
> > > Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > >   
> > > > Add support to parse mdev class id table.
> > > >
> > > > Reviewed-by: Parav Pandit <parav@xxxxxxxxxxxx>
> > > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > > ---
> > > >    drivers/vfio/mdev/vfio_mdev.c     |  2 ++
> > > >    scripts/mod/devicetable-offsets.c |  3 +++
> > > >    scripts/mod/file2alias.c          | 10 ++++++++++
> > > >    3 files changed, 15 insertions(+)
> > > >
> > > > diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c
> > > > index 7b24ee9cb8dd..cb701cd646f0 100644
> > > > --- a/drivers/vfio/mdev/vfio_mdev.c
> > > > +++ b/drivers/vfio/mdev/vfio_mdev.c
> > > > @@ -125,6 +125,8 @@ static const struct mdev_class_id id_table[] = {
> > > >    	{ 0 },
> > > >    };
> > > >    
> > > > +MODULE_DEVICE_TABLE(mdev, id_table);
> > > > +
> > > Two questions, first we have:
> > >
> > > #define MODULE_DEVICE_TABLE(type, name)                                 \
> > > extern typeof(name) __mod_##type##__##name##_device_table               \
> > >     __attribute__ ((unused, alias(__stringify(name))))
> > >
> > > Therefore we're defining __mod_mdev__id_table_device_table with alias
> > > id_table.  When the virtio mdev bus driver is added in 5/6 it uses the
> > > same name value.  I see virtio types all register this way (virtio,
> > > id_table), so I assume there's no conflict, but pci types mostly (not
> > > entirely) seem to use unique names.  Is there a preference to one way
> > > or the other or it simply doesn't matter?
> >
> > It looks to me that those symbol were local, so it doesn't matter. But
> > if you wish I can switch to use unique name.
> I don't have a strong opinion, I'm just trying to make sure we're not
> doing something obviously broken.


Yes, to be more safe I will switch to unique names here.


> > > >    static struct mdev_driver vfio_mdev_driver = {
> > > >    	.name	= "vfio_mdev",
> > > >    	.probe	= vfio_mdev_probe,
> > > > diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
> > > > index 054405b90ba4..6cbb1062488a 100644
> > > > --- a/scripts/mod/devicetable-offsets.c
> > > > +++ b/scripts/mod/devicetable-offsets.c
> > > > @@ -231,5 +231,8 @@ int main(void)
> > > >    	DEVID(wmi_device_id);
> > > >    	DEVID_FIELD(wmi_device_id, guid_string);
> > > >    
> > > > +	DEVID(mdev_class_id);
> > > > +	DEVID_FIELD(mdev_class_id, id);
> > > > +
> > > >    	return 0;
> > > >    }
> > > > diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> > > > index c91eba751804..d365dfe7c718 100644
> > > > --- a/scripts/mod/file2alias.c
> > > > +++ b/scripts/mod/file2alias.c
> > > > @@ -1335,6 +1335,15 @@ static int do_wmi_entry(const char *filename, void *symval, char *alias)
> > > >    	return 1;
> > > >    }
> > > >    
> > > > +/* looks like: "mdev:cN" */
> > > > +static int do_mdev_entry(const char *filename, void *symval, char *alias)
> > > > +{
> > > > +	DEF_FIELD(symval, mdev_class_id, id);
> > > > +
> > > > +	sprintf(alias, "mdev:c%02X", id);
> > > A lot of entries call add_wildcard() here, should we?  Sorry for the
> > > basic questions, I haven't played in this code.  Thanks,
> >
> > It's really good question. My understanding is we won't have a module
> > that can deal with all kinds of classes like CLASS_ID_ANY. So there's
> > probably no need for the wildcard.
> The comment for add_wildcard() indicates future extension, so it's hard
> to know what we might need in the future until we do need it.  The
> majority of modules.alias entries on my laptop (even if I exclude pci
> aliases) end with a wildcard.  Thanks,


Yes, so I will add that for future extension.

Thanks


> Alex