On 12/13/2012 01:57 AM, Thierry Reding wrote: > On Thu, Dec 13, 2012 at 10:48:55AM +0200, Terje Bergström wrote: >> On 12.12.2012 18:08, Thierry Reding wrote: >>> I've briefly discussed this with Stephen on IRC because I >>> thought I had remembered him objecting to the idea of adding a >>> dummy device just for this purpose. It turns out, however, that >>> what he didn't like was to add a dummy node to the DT just to >>> make this happen, but he has no (strong) objections to a dummy >>> platform device. >>> >>> While I'm not very happy about that solution, I've been going >>> over it for a week now and haven't come up with any better >>> alternative that doesn't have its own disadvantages. So perhaps >>> we should go ahead and implement that. For the host1x driver >>> this really just means creating a platform device and adding it >>> to the system, with some of the fields tweaked to make things >>> work. >> >> Even the virtual device is not too beautiful. The problem is that >> the virtual device is not physical parent for DC, HDMI, etc, so >> dev_get_drvdata(pdev->dev.parent) returns the data from host1x >> device, not the virtual device. >> >> We'll post with something that goes around this, but it's not >> going to be too pretty. Let's try to find the solution once we >> get the code out. > > After some more discussion with Stephen on IRC we came to the > conclusion that the easiest might be to have tegra-drm call into > host1x with something like: > > void host1x_set_drm_device(struct host1x *host1x, struct device > *dev); If host1x is registering the dummy device that causes tegradrm to be instantiated, then presumably there's no need for the API above, since host1x will already have the struct device * for tegradrm, since it created it? > Once the dummy device has been properly set up and have each client > use > > struct device *host1x_get_drm_device(struct host1x *host1x); > > to obtain a pointer to the dummy device, such that it can receive > the driver-private data using dev_get_drvdata() on the returned > device. As long as tegra-drm hasn't registered with host1x yet, the > above function could return ERR_PTR(-EPROBE_DEFER), so that > dependencies are automatically handled. This is required because, > tegra-drm not being the parent of the child devices, it can be > guaranteed that it is probed before any of the children. > > That way we should be able to get around any circular > dependencies, since we only call into host1x from tegra-drm but not > the other way around. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
