RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Biju Das]

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.

I am not sure, is this proposal acceptable to wider people??


> but I do not want driver
> writers to learn about multiple <bus-prefix>_get_match_data()
> implementations, I would prefer if they could call
> device_get_match_data() and the right thing happened in all cases.

The driver is bus specific. So I don't know, why you want to
be it generic. If it is i2c client, like other I2C api call the bus-subsystem api for match_data. Similarly, if it is spi client, do the same.

Cheers,
Biju

Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Dmitry Torokhov]

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

RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Biju Das]

Hi Dmitry Torokhov,

Thanks for the feedback.

> Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> 
> 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?
> > > >
> > > >
> > > > 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...):

Looks it will work.

But there is some 2 additional checks in core code, every driver which is not bus type need to go through this checks.

Also in Bus specific callback, there are 2 additional checks.

So, performance wise [1] is better.

Moreover, we need to avoid code duplication with [1]

[1] https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/i2c/i2c-core-base.c#L125

What core people thinking about Dmitry's proposal?

Cheers,
Biju


> 
> 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

Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Dmitry Torokhov]

On Sat, Jul 22, 2023 at 05:51:17PM +0000, Biju Das wrote:
> Hi Dmitry Torokhov,
>
> Thanks for the feedback.
>
> > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> >
> > 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?
> > > > >
> > > > >
> > > > > 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...):
>
> Looks it will work.
>
> But there is some 2 additional checks in core code, every driver which is not bus type need to go through this checks.
>
> Also in Bus specific callback, there are 2 additional checks.
>
> So, performance wise [1] is better.

I do not believe this is a concern whatsoever: majority of
architectures/boards have been converted to ACPI/DT, which are being
matched first as they are now, so the fallback to bus-specific matching
against bus-specific device ID tables will be very infrequent.
Additionally, device_get_match_data() is predominantly called from
driver probe paths, so we need not be concerned with it being used with
class devices or other kinds of devices not associated with a bus.

>
> Moreover, we need to avoid code duplication with [1]
>
> [1] https://elixir.bootlin.com/linux/v6.5-rc2/source/drivers/i2c/i2c-core-base.c#L125

If and when my proposed solution gets into the kernel we can drop
i2c_get_match_data() altogether.

Thanks.


--
Dmitry

RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Biju Das]

Hi Dmitry,

Thanks for the feedback.

> Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> 
> On Sat, Jul 22, 2023 at 05:51:17PM +0000, Biju Das wrote:
> > Hi Dmitry Torokhov,
> >
> > Thanks for the feedback.
> >
> > > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> > >
> > > 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?
> > > > > >
> > > > > >
> > > > > > 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...):
> >
> > Looks it will work.
> >
> > But there is some 2 additional checks in core code, every driver which
> is not bus type need to go through this checks.
> >
> > Also in Bus specific callback, there are 2 additional checks.
> >
> > So, performance wise [1] is better.
> 
> I do not believe this is a concern whatsoever: majority of
> architectures/boards have been converted to ACPI/DT, which are being
> matched first as they are now, so the fallback to bus-specific matching
> against bus-specific device ID tables will be very infrequent.
> Additionally, device_get_match_data() is predominantly called from
> driver probe paths, so we need not be concerned with it being used with
> class devices or other kinds of devices not associated with a bus.

Looks like most of the i2c client driver uses similar handling for 
ACPI/DT and ID tables. If that is the case, it is good to have this
proposed change which will simplify most of the drivers listed in [1]

[1] https://elixir.bootlin.com/linux/latest/A/ident/i2c_match_id

Eg: drivers/hwmon/pmbus/ibm-cffps.c

	enum versions vs = cffps_unknown;
	const void *md = of_device_get_match_data(&client->dev);
	const struct i2c_device_id *id;

	if (md) {
		vs = (enum versions)md;
	} else {
		id = i2c_match_id(ibm_cffps_id, client);
		if (id)
			vs = (enum versions)id->driver_data;
	}

The above code can be converted to 
     vs = (enum versions)device_get_match_data(&client->dev);

> 
> >
> > Moreover, we need to avoid code duplication with [1]
> >
> > [1]
> 
> If and when my proposed solution gets into the kernel we can drop
> i2c_get_match_data() altogether.

Agreed. Will wait for other people's view on this topic.

Cheers,
Biju

RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Biju Das]

> Subject: RE: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> 
> Hi Dmitry,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> >
> > On Sat, Jul 22, 2023 at 05:51:17PM +0000, Biju Das wrote:
> > > Hi Dmitry Torokhov,
> > >
> > > Thanks for the feedback.
> > >
> > > > Subject: Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()
> > > >
> > > > 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?
> > > > > > >
> > > > > > >
> > > > > > > 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...):
> > >
> > > Looks it will work.
> > >
> > > But there is some 2 additional checks in core code, every driver
> > > which
> > is not bus type need to go through this checks.
> > >
> > > Also in Bus specific callback, there are 2 additional checks.
> > >
> > > So, performance wise [1] is better.
> >
> > I do not believe this is a concern whatsoever: majority of
> > architectures/boards have been converted to ACPI/DT, which are being
> > matched first as they are now, so the fallback to bus-specific
> > matching against bus-specific device ID tables will be very
> infrequent.
> > Additionally, device_get_match_data() is predominantly called from
> > driver probe paths, so we need not be concerned with it being used
> > with class devices or other kinds of devices not associated with a
> bus.
> 
> Looks like most of the i2c client driver uses similar handling for
> ACPI/DT and ID tables. If that is the case, it is good to have this
> proposed change which will simplify most of the drivers listed in [1]
> 
> [1]
> https://jpn01.safelinks.protection.outlook.com/?url=https%3A%2F%2Felixir
> .bootlin.com%2Flinux%2Flatest%2FA%2Fident%2Fi2c_match_id&data=05%7C01%7C
> biju.das.jz%40bp.renesas.com%7C2a07c353ab7649fdf29a08db8b42cca3%7C53d825
> 71da1947e49cb4625a166a4a2a%7C0%7C0%7C638256891245437404%7CUnknown%7CTWFp
> bGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%
> 3D%7C3000%7C%7C%7C&sdata=tOxuTgGKc%2FQYFx94rYUJ8TDTWmGKkETzASV3qUjP2vk%3
> D&reserved=0
> 
> Eg: drivers/hwmon/pmbus/ibm-cffps.c
> 
> 	enum versions vs = cffps_unknown;
> 	const void *md = of_device_get_match_data(&client->dev);
> 	const struct i2c_device_id *id;
> 
> 	if (md) {
> 		vs = (enum versions)md;
> 	} else {
> 		id = i2c_match_id(ibm_cffps_id, client);
> 		if (id)
> 			vs = (enum versions)id->driver_data;
> 	}
> 
> The above code can be converted to
>      vs = (enum versions)device_get_match_data(&client->dev);
> 
> >
> > >
> > > Moreover, we need to avoid code duplication with [1]
> > >
> > > [1]
> >
> > If and when my proposed solution gets into the kernel we can drop
> > i2c_get_match_data() altogether.
> 
> Agreed. Will wait for other people's view on this topic.

Also remove spi_get_device_match_data and
Make i2c_match_id() and spi_get_device_id() as static and

Replace all these with device_get_natch_data() from all i2c/spi client drivers.

Can you please post a patch based on this?

Cheers,
Biju

Re: [PATCH v2 1/2] Input: exc3000 - Simplify probe()

[Dmitry Torokhov]

On Sun, Jul 23, 2023 at 06:50:29AM +0000, Biju Das wrote:
> 
> Can you please post a patch based on this?

It looks like you are already taking care of this so I'll let you
finish.

Thanks.

-- 
Dmitry