On Mon, Feb 19, 2018 at 11:59:23PM +0100, Daniel Vetter wrote: > 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). I disagree. module_get() is only going to protect you from unloading a module that's in use, but there are other ways to unbind a driver from the device and cause subsequent mayhem. struct device_link was "recently" introduced to fix that issue. Thierry
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