On Mon, Feb 19, 2018 at 10:06:22PM +0200, Jyri Sarha wrote: > Currently there is no way for a master drm driver to protect against an > attached panel driver from being unloaded while it is in use. The > least we can do is to indicate the usage by incrementing the module > reference count. > > Signed-off-by: Jyri Sarha <jsarha@xxxxxx> > cc: eric@xxxxxxxxxx > cc: laurent.pinchart@xxxxxxxxxxxxxxxx > --- > I do not see any module_get/put code in drm core. Is there is a reason > for that? > > There is two more alternative places for adding the module_get/put > code. One is puting it directly to drm_panel_attach() and > drm_panel_detach(). However, if the same module implements both the > master drm driver and the panel (like tilcdc does with its > tilcdc_panel.c), then attaching the panel will lock the module in for > no good reason. Still, this solution should work with drm bridges as I > do not see any reason why anybody would implement bridge drivers in > the same module with the master drm driver. > > The other place to put the code would in the master drm driver. But > for handling the situation with bridges would need the device pointer > in struct drm_bridge. I think this looks like a reasonable place to do this. Looking at the code we seem to have a similar issue with the bridge driver itself. I think we need to wire through the module owner stuff and add a try_modeul_get to of_drm_find_bridge (and any other helper used to find bridge instances). Care to look into that part of the problem, too? -Daniel > > drivers/gpu/drm/bridge/panel.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c > index 6d99d4a..0a10be6 100644 > --- a/drivers/gpu/drm/bridge/panel.c > +++ b/drivers/gpu/drm/bridge/panel.c > @@ -161,6 +161,10 @@ struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel, > if (!panel) > return ERR_PTR(-EINVAL); > > + if (WARN_ON(!panel->dev->driver) || > + !try_module_get(panel->dev->driver->owner)) > + return ERR_PTR(-ENODEV); > + > panel_bridge = devm_kzalloc(panel->dev, sizeof(*panel_bridge), > GFP_KERNEL); > if (!panel_bridge) > @@ -199,6 +203,9 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge) > panel_bridge = drm_bridge_to_panel_bridge(bridge); > > drm_bridge_remove(bridge); > + > + module_put(panel_bridge->panel->dev->driver->owner); > + > devm_kfree(panel_bridge->panel->dev, bridge); > } > EXPORT_SYMBOL(drm_panel_bridge_remove); > -- > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
