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Date:   Fri, 21 Jul 2023 15:10:02 -0700
From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Biju Das <biju.das.jz@bp.renesas.com>
Cc:     Mark Brown <broonie@kernel.org>,
        Mike Looijmans <mike.looijmans@topic.nl>,
        Andreas Helbech Kleist <andreaskleist@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        "linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
        "linux-renesas-soc@vger.kernel.org" 
        <linux-renesas-soc@vger.kernel.org>,
        Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
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On Wed, Jul 19, 2023 at 06:43:47AM +0000, Biju Das wrote:
> Hi Dmitry Torokhov,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> > 
> > On Mon, Jul 17, 2023 at 06:45:27PM +0000, Biju Das wrote:
> > > Hi Dmitry,
> > >
> > > > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> > > >
> > > > On Mon, Jul 17, 2023 at 07:15:50PM +0100, Mark Brown wrote:
> > > > > On Mon, Jul 17, 2023 at 04:35:02PM +0000, Biju Das wrote:
> > > > >
> > > > > > The .device_get_match_data callbacks are missing for I2C and SPI
> > > > > > bus
> > > > subsystems.
> > > > > > Can you please throw some lights on this?
> > > > >
> > > > > It's the first time I've ever heard of that callback, I don't know
> > > > > why whoever added it wouldn't have done those buses in particular
> > > > > or if it just didn't happen.  Try adding it and if it works send
> > the patches?
> > > >
> > > > I think there is a disconnect. Right now device_get_match_data
> > > > callbacks are part of fwnode_operations. I was proposing to add
> > > > another optional device_get_match_data callback to 'struct bus_type'
> > > > to allow individual buses control how match data is handled, before
> > > > (or after) jumping into the fwnode-backed device_get_match_data
> > callbacks.
> > >
> > > That is what implemented here [1] and [2] right?
> 
> [1] https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/spi/spi.c#L364
> 
> [2] https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/i2c/i2c-core-base.c#L117
> 
> > >
> > >
> > > First it check for fwnode-backed device_get_match_data callbacks and
> > > Fallback is bus-type based match.
> > >
> > > Looks like you are proposing to unify [1] and [2] and you want the
> > > logic to be other way around. ie, first bus-type match, then
> > > fwnode-backed callbacks?
> > >
> > 
> > I do not have a strong preference for the ordering, i.e. I think it is
> > perfectly fine to do the generic fwnode-based lookup and if there is no
> > match have bus method called as a fallback, 
> 
> That involves a bit of work.
> 
> const void *device_get_match_data(const struct device *dev);
> 
> const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
> 					 const struct i2c_client *client);
> 
> const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev);
> 
> Basically, the bus-client driver(such as exc3000) needs to pass struct device
> and device_get_match_data after generic fwnode-based lookup,
> needs to find the bus type based on struct device and call a new generic 
> void* bus_get_match_data(void*) callback, so that each bus interface
> can do a match.

Yes, something like this (which does not seem that involved to me...):

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 8c40abed7852..cc0bf7bb6f3a 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -1277,7 +1277,13 @@ EXPORT_SYMBOL(fwnode_graph_parse_endpoint);
 
 const void *device_get_match_data(const struct device *dev)
 {
-	return fwnode_call_ptr_op(dev_fwnode(dev), device_get_match_data, dev);
+	const void *data;
+
+	data = fwnode_call_ptr_op(dev_fwnode(dev), device_get_match_data, dev);
+	if (!data && dev->bus && dev->bus->get_match_data)
+		data = dev->bus->get_match_data(dev);
+
+	return data;
 }
 EXPORT_SYMBOL_GPL(device_get_match_data);
 
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 60746652fd52..5fe47bc491a6 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -114,6 +114,26 @@ const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
 }
 EXPORT_SYMBOL_GPL(i2c_match_id);
 
+static const void *i2c_device_get_match_data(const struct device *dev)
+{
+	const struct i2c_client *client = to_i2c_client(dev);
+	const struct i2c_driver *driver;
+	const struct i2c_device_id *match;
+
+	if (!dev->driver)
+		return NULL;
+
+	driver = to_i2c_driver(dev->driver);
+	if (!driver)
+		return NULL;
+
+	match = i2c_match_id(driver->id_table, client);
+	if (!match)
+		return NULL;
+
+	return (const void *)match->driver_data;
+}
+
 const void *i2c_get_match_data(const struct i2c_client *client)
 {
 	struct i2c_driver *driver = to_i2c_driver(client->dev.driver);
@@ -695,6 +715,7 @@ struct bus_type i2c_bus_type = {
 	.probe		= i2c_device_probe,
 	.remove		= i2c_device_remove,
 	.shutdown	= i2c_device_shutdown,
+	.get_match_data	= i2c_device_get_match_data,
 };
 EXPORT_SYMBOL_GPL(i2c_bus_type);
 
diff --git a/include/linux/device/bus.h b/include/linux/device/bus.h
index ae10c4322754..3f2cba28a1af 100644
--- a/include/linux/device/bus.h
+++ b/include/linux/device/bus.h
@@ -102,6 +102,8 @@ struct bus_type {
 	int (*dma_configure)(struct device *dev);
 	void (*dma_cleanup)(struct device *dev);
 
+	const void *(*get_match_data)(const struct device *dev);
+
 	const struct dev_pm_ops *pm;
 
 	const struct iommu_ops *iommu_ops;


Thanks.

-- 
Dmitry