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

[Thierry Reding <thierry.reding@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 1942 bytes --]

On Wed, Feb 06, 2019 at 10:49:12AM +0100, Wolfram Sang wrote:
> 
> > And there is a regression! Good that I didn't push out before
> > double-checking. No one noticed that this breaks registering child
> > devices because of_i2c_register_devices() doesn't have a pointer to work
> > with anymore?
> 
> Well, sorry, I forgot an important detail. There is no regression
> because most drivers still populate adap->dev.of_data with the node
> pointer of their parent. I experimentally removed this from my driver
> under test motivated by this comment from the commit in the Fixes: tag:
> 
> "Linking it to the device node of the parent device is wrong, as it
> leads to 2 devices sharing the same device node, which is bad practice,"
> 
> But removing this bad practice from I2C core is more work. I wonder now
> if we are in some inconsistent in-between state if I apply this patch as
> is?

I think this patch would serve as preparatory work to remove the sharing
of device nodes. There shouldn't be any regressions here because we only
fall back to the parent's ->of_node if the I2C adapter's ->of_node does
not match. Since the I2C adapter's ->of_node match is what we currently
do, the only thing that this patch does is add a fallback for the cases
where the I2C adapter's ->of_node is not set.

As far as I can tell, the only code where this should matter is the
drm_dp_aux helpers where the I2C adapter's ->of_node is no longer being
set because of the commit that introduced the regression for Tegra124
Nyan (and Venice2) boards.

So I think this patch is safe to apply and as you suggested this can be
used as the baseline for cleaning up all the cases where we reuse the
parent's ->of_node for the I2C adapter's ->of_node.

So I guess you could say we're in some in-between state, but I don't
think it's inconsistent. It just allows us to do this step by step,
which I think is good.

Thierry

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[-- Attachment #2: Type: text/plain, Size: 160 bytes --]

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel