Any update on this patch? I thought it was interesting. BTW adding Rob (finally) to CC... On Mon, Oct 01, 2018 at 01:02:30AM +0200, Wolfram Sang wrote: > On Tue, Sep 25, 2018 at 06:06:11PM +0200, Thierry Reding wrote: > > From: Thierry Reding <treding@xxxxxxxxxx> > > > > If an I2C adapter doesn't match the provided device tree node, also try > > matching the parent's device tree node. This allows finding an adapter > > based on the device node of the parent device that was used to register > > it. > > > > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> > > --- > > Hi Wolfram, > > > > This is a fix for the issue discussed in a long email thread a couple of > > months ago. In a nutshell the issue is that we want to be able to find a > > I2C-over-AUX adapter based on the device tree node (this is to hook up a > > I2C adapter for use as DDC to query EDID from a display panel, for > > example). > > > > Here's a link to the prior discussion, which ended up getting split into > > two for some reason, possibly because the initial submission and > > subsequent discussion took place over an extended period of time: > > > > https://patchwork.kernel.org/patch/9516105/ > > https://patchwork.kernel.org/patch/10200879/ > > Ok, I read that... > > > > > I never got around to submitting the patch properly, but here it is. As > > mentioned in the discussion linked to above, I think the problem here is > > that the new lookup via the parent device only happens when looking for > > the adapter from its device tree node. However, this also means that the > > children for the controller won't be added for these devices, because it > > only happens for adapters that have the dev->of_node set, not for the > > node reference by dev->parent->of_node. However, I'm not sure if that's > > really a problem. A device that doesn't have dev->of_node set would be a > > "virtual" I2C bus, as in the case of I2C-over-AUX. Proper I2C busses are > > still going to have to have their dev->of_node set, otherwise any child > > devices listed in device tree won't be added. > > > > Anyway, let me know what you think of this. Also adding Lucas, Rob and > > Andrzej to the discussion since they were involved back at the time. > > ... and it looks okay from that discussion point of view. And we could > stop reusing the parent's of_node for the adapter's of_node. Which is > better practice. Rob, can you confirm. > > > diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c > > index 6cb7ad608bcd..37d34885ea2d 100644 > > --- a/drivers/i2c/i2c-core-of.c > > +++ b/drivers/i2c/i2c-core-of.c > > @@ -121,6 +121,14 @@ static int of_dev_node_match(struct device *dev, void *data) > > return dev->of_node == data; > > } > > > > +static int of_parent_node_match(struct device *dev, void *data) > > +{ > > + if (dev->parent) > > + return dev->parent->of_node == data; > > + > > + return 0; > > +} > > + > > /* must call put_device() when done with returned i2c_client device */ > > struct i2c_client *of_find_i2c_device_by_node(struct device_node *node) > > { > > @@ -146,6 +154,9 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node) > > struct i2c_adapter *adapter; > > > > dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match); > > + if (!dev) > > + dev = bus_find_device(&i2c_bus_type, NULL, node, of_parent_node_match); > > + > > To avoid the double loop iteration, maybe introduce > 'of_dev_or_parent_node_match' and merge those two functionalities? > > Regards, > > Wolfram
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