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

Alex Williamson
2019-10-23T21:43:21Z

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?

> 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,

Alex

> + return 1;
> +}
> +
> /* Does namelen bytes of name exactly match the symbol? */
> static bool sym_is(const char *name, unsigned namelen, const char *symbol)
> {
> @@ -1407,6 +1416,7 @@ static const struct devtable devtable[] = {
> {"typec", SIZE_typec_device_id, do_typec_entry},
> {"tee", SIZE_tee_client_device_id, do_tee_entry},
> {"wmi", SIZE_wmi_device_id, do_wmi_entry},
> + {"mdev", SIZE_mdev_class_id, do_mdev_entry},
> };
>
> /* Create MODULE_ALIAS() statements.