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

Alex Williamson
2019-10-24T19:55:04Z

On Thu, 24 Oct 2019 11:31:04 +0800
Jason Wang <jasowang@redhat.com> wrote:

> On 2019/10/24 上午5:42, Alex Williamson wrote:
> > On Wed, 23 Oct 2019 21:07:48 +0800
> > Jason Wang <jasowang@redhat.com> wrote:
> >
> >> Add support to parse mdev class id table.
> >>
> >> Reviewed-by: Parav Pandit <parav@mellanox.com>
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >> ---
> >> 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.

> >> 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,

Alex