On Thu, Aug 15, 2013 at 03:32:58PM -0400, Sean Paul wrote: > On Thu, Aug 15, 2013 at 11:28 AM, Thierry Reding > <thierry.reding@xxxxxxxxx> wrote: > > On Wed, Aug 14, 2013 at 04:47:38PM -0400, Sean Paul wrote: > > [...] > >> +int ptn3460_init(struct drm_device *dev, struct drm_encoder *encoder, > >> + struct i2c_client *client, struct device_node *node) > > [...] > >> + ptn_bridge->gpio_pd_n = of_get_named_gpio(node, "powerdown-gpio", 0); > > > > of_get_named_gpio() can return -EPROBE_DEFER and I wonder how you handle > > that in the driver that uses ptn3460_init(). Since you pass in an > > initialized drm_device, you'd need to undo all of that in case of > > -EPROBE_DEFER. Well I guess you'd have to do that in case of any error, > > but it makes things difficult to handle for drivers. > > > > For instance on Tegra we pretty much delay DRM initialization until all > > required subdevices (there are quite a few) have been probed, so if we > > wanted to use this function we'd have to call it after all drivers have > > been probed because only then do we have access to a struct drm_device. > > That will cause other problems, however, because at that point we can't > > defer probing anymore. > > > > I suppose I could add another init that performs the deferrable tasks > (ptn3460_init_deferrable or something). This would be called before > drm init has been started from one of the probe functions. > Alternatively, I could set this up as a standalone i2c driver and do > this stuff in the probe. Any other options? My point was that in those cases you don't have access to the DRM device yet since you haven't called drm_init() yet. > Adding another init call adds yet another thing the drm driver has to > do to use this bridge. Making the ptn driver standalone requires you > to set things up such that drm init is dependent on ptn probe running > successfully. I'm not sure which is more desirable. > > Practically speaking, do you expect to call drm_init before the gpio > is available? No, not really, but I won't know that the GPIO is available until I actually call of_get_named_gpio_flags(). But perhaps we should cross that bridge when we get to it. Thierry
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