[PATCH v2] i2c: of: Try to find an I2C adapter matching the parent

[Thierry Reding]

On Mon, Jan 28, 2019 at 09:08:15AM +0100, Thierry Reding wrote:
> On Sat, Jan 26, 2019 at 01:37:34PM +0100, Tristan Bastian wrote:
> > Am 25.01.19 um 14:11 schrieb Thierry Reding:
> > > From: Thierry Reding <treding at nvidia.com>
> > > 
> > > 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.
> > > 
> > > This fixes a regression on Tegra124-based Chromebooks (Nyan) where the
> > > eDP controller registers an I2C adapter that is used to read to EDID.
> > > After commit 993a815dcbb2 ("dt-bindings: panel: Add missing .txt
> > > suffix") this stopped working because the I2C adapter could no longer
> > > be found. The approach in this patch fixes the regression without
> > > introducing the issues that the above commit solved.
> > > 
> > > Fixes: 17ab7806de0c ("drm: don't link DP aux i2c adapter to the hardware device node")
> > > Signed-off-by: Thierry Reding <treding at nvidia.com>
> > > ---
> > > Changes in v2:
> > > - check for both device and parent device tree nodes for each device
> > >    instead of looping through the list of devices twice
> > > 
> > >   drivers/i2c/i2c-core-of.c | 14 +++++++++++++-
> > >   1 file changed, 13 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
> > > index 6cb7ad608bcd..0f01cdba9d2c 100644
> > > --- a/drivers/i2c/i2c-core-of.c
> > > +++ b/drivers/i2c/i2c-core-of.c
> > > @@ -121,6 +121,17 @@ static int of_dev_node_match(struct device *dev, void *data)
> > >   	return dev->of_node == data;
> > >   }
> > > +static int of_dev_or_parent_node_match(struct device *dev, void *data)
> > > +{
> > > +	if (dev->of_node == data)
> > > +		return 1;
> > > +
> > > +	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)
> > >   {
> > > @@ -145,7 +156,8 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
> > >   	struct device *dev;
> > >   	struct i2c_adapter *adapter;
> > > -	dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match);
> > > +	dev = bus_find_device(&i2c_bus_type, NULL, node,
> > > +			      of_dev_or_parent_node_match);
> > >   	if (!dev)
> > >   		return NULL;
> > 
> > I've tested this and can confirm that this fixes the issue on the nyan-big
> > chromebook.
> 
> Excellent, thanks for testing! Typically if you've tested a patch and
> verified that it fixes the problem that you were seeing, it's good to
> send this on a line by itself along with your reply:
> 
> Tested-by: Tristan Bastian <tristan-c.bastian at gmx.de>

Oh my... that was stupid. I think patchwork might now pick this up...

This also made me realize that I should've credited both Tristan and
Vlado as reporters in the commit message. I'll resend this.

Tristan, is it okay if I include your Tested-by: tag in the v2?

Thierry
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