On Thu, Jun 09, 2016 at 09:57:24PM +0100, Chris Wilson wrote: > On Fri, Jun 03, 2016 at 05:59:11PM +0300, Ville Syrjälä wrote: > > On Fri, Jun 03, 2016 at 03:36:49PM +0100, Chris Wilson wrote: > > > When trying to split up the initialisation phase and the registration > > > phase, one immediate problem encountered is trying to use our own i2c > > > devices before registration with userspace (to read EDID during device > > > discovery). drm_dp_aux in particular only offers an interface for setting > > > up the device *after* we have exposed the connector via sysfs. In order > > > to break the chicken-and-egg problem, export drm_dp_aux_init() to > > > minimally prepare the i2c device for internal use before > > > drm_connector_register(). > > > > > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> > > > Cc: Dave Airlie <airlied at redhat.com> > > > Cc: Rafael Antognolli <rafael.antognolli at intel.com> > > > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com> > > > Cc: dri-devel at lists.freedesktop.org > > > --- > > > drivers/gpu/drm/drm_dp_helper.c | 26 +++++++++++++++++++++----- > > > include/drm/drm_dp_helper.h | 1 + > > > 2 files changed, 22 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_dp_helper.c > > > b/drivers/gpu/drm/drm_dp_helper.c > > > index 4b088afa21b2..9b4ec65e1de6 100644 > > > --- a/drivers/gpu/drm/drm_dp_helper.c > > > +++ b/drivers/gpu/drm/drm_dp_helper.c > > > @@ -791,15 +791,16 @@ static void unlock_bus(struct i2c_adapter *i2c, > > > unsigned int flags) > > > } > > > > > > /** > > > - * drm_dp_aux_register() - initialise and register aux channel > > > + * drm_dp_aux_init() - minimally initialise an aux channel > > > * @aux: DisplayPort AUX channel > > > * > > > - * Returns 0 on success or a negative error code on failure. > > > + * If you need to use the drm_dp_aux's i2c adapter prior to registering > > > it > > > + * with the outside world, call drm_dp_aux_init() first. You must still > > > + * call drm_dp_aux_register() once the connector has been registered to > > > + * allow userspace access to the auxiliary DP channel. > > > */ > > > -int drm_dp_aux_register(struct drm_dp_aux *aux) > > > +void drm_dp_aux_init(struct drm_dp_aux *aux) > > > { > > > - int ret; > > > - > > > mutex_init(&aux->hw_mutex); > > > > > > aux->ddc.algo = &drm_dp_i2c_algo; > > > @@ -809,6 +810,21 @@ int drm_dp_aux_register(struct drm_dp_aux *aux) > > > aux->ddc.lock_bus = lock_bus; > > > aux->ddc.trylock_bus = trylock_bus; > > > aux->ddc.unlock_bus = unlock_bus; > > > +} > > > +EXPORT_SYMBOL(drm_dp_aux_init); > > > > This doesn't feel very safe to me. To me it looks like the i2c core > > wasn't designed to have the adapter be used before i2c_add_adapter() > > is called. I guess it might work in this case since you provide your > > own lock vfuncs. > > > > I think someone should fix the i2c core to split i2c_add_adapter() > > & co. into init and register phases. Cc:ing i2c folks... > > As you've seen, I sent the patches to split i2c_add_adapter() to allow for > us to call i2c_init_adapter() here instead. It still requires the same > basic review that this init (the same as above) is sufficient for using > i2c_transfer(). > > I would like to get the regression fix completed without much futher > ado - in particular, not depending upon landing an external patch.
What regression is this? -- Ville Syrjälä Intel OTC