linux-kernel - Re: [PATCH v7 06/10] i2c: Introduce OF component probe function

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Message-ID: <ZugKHrzs5BWoDr1c@smile.fi.intel.com>
Date: Mon, 16 Sep 2024 13:36:14 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Chen-Yu Tsai <wenst@...omium.org>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Wolfram Sang <wsa@...nel.org>, Benson Leung <bleung@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>, Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	chrome-platform@...ts.linux.dev, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Johan Hovold <johan@...nel.org>, Jiri Kosina <jikos@...nel.org>,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v7 06/10] i2c: Introduce OF component probe function

On Sun, Sep 15, 2024 at 12:44:13PM +0200, Chen-Yu Tsai wrote:
> On Fri, Sep 13, 2024 at 12:25 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Wed, Sep 11, 2024 at 03:27:44PM +0800, Chen-Yu Tsai wrote:

...

> > > +int i2c_of_probe_component(struct device *dev, const struct i2c_of_probe_cfg *cfg, void *ctx)
> > > +{
> > > +     const struct i2c_of_probe_ops *ops;
> > > +     const char *type;
> > > +     struct device_node *i2c_node;
> > > +     struct i2c_adapter *i2c;
> > > +     int ret;
> > > +
> > > +     if (!cfg)
> > > +             return -EINVAL;
> > > +
> > > +     ops = cfg->ops ?: &i2c_of_probe_dummy_ops;
> > > +     type = cfg->type;
> > > +
> > > +     i2c_node = i2c_of_probe_get_i2c_node(dev, type);
> >
> >
> >         struct device_node *i2c_node __free(of_node_put) =
> >                 i2c_...;
> 
> cleanup.h says to not mix the two styles (scoped vs goto). I was trying
> to follow that, though I realize now that with the scoped loops it
> probably doesn't help.
> 
> I'll revert back to having __free().
> 
> > > +     if (IS_ERR(i2c_node))
> > > +             return PTR_ERR(i2c_node);
> > > +
> > > +     for_each_child_of_node_with_prefix(i2c_node, node, type) {
> > > +             if (!of_device_is_available(node))
> > > +                     continue;
> > > +
> > > +             /*
> > > +              * Device tree has component already enabled. Either the
> > > +              * device tree isn't supported or we already probed once.
> > > +              */
> > > +             ret = 0;
> >
> > Shouldn't you drop reference count for "node"? (See also below)
> 
> This for-each loop the "scoped". It just doesn't have the prefix anymore.
> I believe you asked if the prefix could be dropped and then Rob agreed.

Hmm... I have looked into the implementation and I haven't found the evidence
that this is anyhow scoped. Can you point out what I have missed?

> > > +             goto out_put_i2c_node;
> > > +     }
> > > +
> > > +     i2c = of_get_i2c_adapter_by_node(i2c_node);
> > > +     if (!i2c) {
> > > +             ret = dev_err_probe(dev, -EPROBE_DEFER, "Couldn't get I2C adapter\n");
> > > +             goto out_put_i2c_node;
> > > +     }
> > > +
> > > +     /* Grab resources */
> > > +     ret = 0;
> > > +     if (ops->get_resources)
> > > +             ret = ops->get_resources(dev, i2c_node, ctx);
> > > +     if (ret)
> > > +             goto out_put_i2c_adapter;
> > > +
> > > +     /* Enable resources */
> > > +     if (ops->enable)
> > > +             ret = ops->enable(dev, ctx);
> > > +     if (ret)
> > > +             goto out_release_resources;
> > > +
> > > +     ret = 0;
> > > +     for_each_child_of_node_with_prefix(i2c_node, node, type) {
> > > +             union i2c_smbus_data data;
> > > +             u32 addr;
> > > +
> > > +             if (of_property_read_u32(node, "reg", &addr))
> > > +                     continue;
> > > +             if (i2c_smbus_xfer(i2c, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &data) < 0)
> > > +                     continue;
> > > +
> > > +             /* Found a device that is responding */
> > > +             if (ops->free_resources_early)
> > > +                     ops->free_resources_early(ctx);
> > > +             ret = i2c_of_probe_enable_node(dev, node);
> >
> > Hmm... Is "node" reference count left bumped up for a reason?
> 
> Same as above.

Same as above.

> > > +             break;
> > > +     }
> > > +
> > > +     if (ops->cleanup)
> > > +             ops->cleanup(dev, ctx);
> > > +out_release_resources:
> > > +     if (ops->free_resources_late)
> > > +             ops->free_resources_late(ctx);
> > > +out_put_i2c_adapter:
> > > +     i2c_put_adapter(i2c);
> > > +out_put_i2c_node:
> > > +     of_node_put(i2c_node);
> > > +
> > > +     return ret;
> > > +}

-- 
With Best Regards,
Andy Shevchenko