[PATCH v4 02/15] include/drm/drm_gem.h: add poll_table_struct forward declaration

[Max Kellermann <max.kellermann@ionos.com>]

After eliminating includes of linux/mm.h, the following build failure
occurred:

 ./include/drm/drm_file.h:443:45: warning: ‘struct poll_table_struct’ declared inside parameter list will not be visible outside of this definition or declaration
   443 | __poll_t drm_poll(struct file *filp, struct poll_table_struct *wait);
       |                                             ^~~~~~~~~~~~~~~~~
 In file included from drivers/gpu/drm/imagination/pvr_gem.h:12,
                  from drivers/gpu/drm/imagination/pvr_fw.h:9:
 ./include/drm/drm_gem.h:447:27: error: initialization of ‘__poll_t (*)(struct file *, struct poll_table_struct *)’ {aka ‘unsigned int (*)(struct file *, struct poll_table_struct *)’} from incompatible pointer type ‘__poll_t (*)(struct file *, struct poll_table_struct *)’ {aka ‘unsigned int (*)(struct file *, struct poll_table_struct *)’} [-Werror=incompatible-pointer-types]
   447 |         .poll           = drm_poll,\
       |                           ^~~~~~~~

The compiler is confused, and that can be fixed easily by
forward-declaring the struct expicitly.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 include/drm/drm_file.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index ab230d3af138..f24ade9f766f 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -44,6 +44,7 @@ struct drm_device;
 struct drm_printer;
 struct device;
 struct file;
+struct poll_table_struct;
 
 /*
  * FIXME: Not sure we want to have drm_minor here in the end, but to avoid
-- 
2.39.2