| Message ID | 20230927102808.18650-3-tzimmermann@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/i915: Convert fbdev to DRM client | expand |
Thomas Zimmermann <tzimmermann@suse.de> writes: > Do not acquire a reference on the module that provides a client's > callback functions in drm_client_init(). The additional reference > prevents the user from unloading the callback functions' module and > thus creating dangling pointers. > > This is only necessary if there is no direct dependency between the > caller of drm_client_init() and the provider of the callbacks in > struct drm_client_funcs. If this case ever existed, it has been > removed from the DRM code. Callers of drm_client_init() also provide > the callback implementation. The lifetime of the clients is tied to > the dependency chain's outer-most module, which is the hardware's > DRM driver. Before client helpers could be unloaded, the driver module > would have to be unloaded, which also unregisters all clients. > > Driver modules that set up DRM clients can now be unloaded. > > Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> > --- The change makes sense to me. Acked-by: Javier Martinez Canillas <javierm@redhat.com>
diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c index 2762572f286e7..b49f91b5d4b27 100644 --- a/drivers/gpu/drm/drm_client.c +++ b/drivers/gpu/drm/drm_client.c @@ -5,7 +5,6 @@ #include <linux/iosys-map.h> #include <linux/list.h> -#include <linux/module.h> #include <linux/mutex.h> #include <linux/seq_file.h> #include <linux/slab.h> @@ -84,16 +83,13 @@ int drm_client_init(struct drm_device *dev, struct drm_client_dev *client, if (!drm_core_check_feature(dev, DRIVER_MODESET) || !dev->driver->dumb_create) return -EOPNOTSUPP; - if (funcs && !try_module_get(funcs->owner)) - return -ENODEV; - client->dev = dev; client->name = name; client->funcs = funcs; ret = drm_client_modeset_create(client); if (ret) - goto err_put_module; + return ret; ret = drm_client_open(client); if (ret) @@ -105,10 +101,6 @@ int drm_client_init(struct drm_device *dev, struct drm_client_dev *client, err_free: drm_client_modeset_free(client); -err_put_module: - if (funcs) - module_put(funcs->owner); - return ret; } EXPORT_SYMBOL(drm_client_init); @@ -177,8 +169,6 @@ void drm_client_release(struct drm_client_dev *client) drm_client_modeset_free(client); drm_client_close(client); drm_dev_put(dev); - if (client->funcs) - module_put(client->funcs->owner); } EXPORT_SYMBOL(drm_client_release);
Do not acquire a reference on the module that provides a client's callback functions in drm_client_init(). The additional reference prevents the user from unloading the callback functions' module and thus creating dangling pointers. This is only necessary if there is no direct dependency between the caller of drm_client_init() and the provider of the callbacks in struct drm_client_funcs. If this case ever existed, it has been removed from the DRM code. Callers of drm_client_init() also provide the callback implementation. The lifetime of the clients is tied to the dependency chain's outer-most module, which is the hardware's DRM driver. Before client helpers could be unloaded, the driver module would have to be unloaded, which also unregisters all clients. Driver modules that set up DRM clients can now be unloaded. Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> --- drivers/gpu/drm/drm_client.c | 12 +----------- 1 file changed, 1 insertion(+), 11 deletions(-)