Re: [PATCH v2 2/3] HID: i2c-hid: Move common ACPI _DSM helper into core

[Hans de Goede <hansg@kernel.org>]

Hi Benjamin,

On 3-Jun-26 11:43 AM, Benjamin Tissoires wrote:
> On Jun 01 2026, 谢致邦 (XIE Zhibang) wrote:
>> Move the _DSM call that gets the HID descriptor address from
>> i2c-hid-acpi.c to a shared helper in i2c-hid-core.c so both
>> i2c-hid-acpi.c and i2c-hid-of.c can use it.
>>
>> Signed-off-by: 谢致邦 (XIE Zhibang) <Yeking@Red54.com>
>> ---
>>  drivers/hid/i2c-hid/i2c-hid-acpi.c | 32 ++++-----------------------
>>  drivers/hid/i2c-hid/i2c-hid-core.c | 35 ++++++++++++++++++++++++++++++
> 
> I'm not a big fan of removing 25% of the i2c-hid-acpi.c code and inject
> it in i2c-hid-core.c.

It is only 35 new lines in i2c-hid-core.c, so it is not that big / much code.

> There's something I can't really understand in the problem:
> - we are talking about non arm architecture, which should not have OF in
> 	them
> - the current compatible hid-over-i2c loads the OF version?
> - how can you make the device working without the couple of ACPI
> 	functions that are in the i2c-hid-acpi.c driver for powering up and
> 	down the device?
> 
> If the platform is indeed ACPI + x86(_64), then shouldn't we tackle the
> problem in the i2c-hid-acpi driver, or add a secondary leaf driver for
> this particular platform/device? Kind of what we have with
> i2c-hid-of-elan.c

As part of the work to use ACPI on ARM systems, it is possible now a days
to inject DT snippets into ACPI tables.

The problem on these Loongson laptops is that they have created this
very ugly mixed-mode where they put a PRP0001 ACPI HID on the ACPI
node for the touchscreen, which means it contains an embedded DT
snippet and in that snipped out "compatible=hid-over-i2c" but NOT
also "i2c-hid-descr-addr=x". To get the i2c-hid descriptor address
the implemented the ACPI _DSM on the same ACPI device/fwnode.

The ACPI core sees HID=PRP0001 so it creates an of-compatible 
modalias / match and not an ACPI one, so the i2c-hid-of driver will
bind.

Note these "fixed" (as in we cannot fix them) ACPI tables use
the generic i2c-over-hid OF/DT compatible _not_ something
more specific so we can also not do a more specific driver like
i2c-hid-of-elan.c. If we could fix the ACPI tables we would just
change the ACPI HID to the standard PNPxxxx ACPI HID for i2c-hid
devices.

The first version of this patch-set added an of match table
to i2c-hid-acpi making it also load and probe i2c-hid devices
described in devicetree on devicetree only systems which IMHO
is very messy.

So this new series is the least ugly way to deal with this.

Regards,

Hans






> 
> Cheers,
> Benjamin
> 
>>  drivers/hid/i2c-hid/i2c-hid.h      | 11 ++++++++++
>>  3 files changed, 50 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/hid/i2c-hid/i2c-hid-acpi.c b/drivers/hid/i2c-hid/i2c-hid-acpi.c
>> index f65fb6396b69..234789a07047 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid-acpi.c
>> +++ b/drivers/hid/i2c-hid/i2c-hid-acpi.c
>> @@ -25,12 +25,12 @@
>>  #include <linux/kernel.h>
>>  #include <linux/module.h>
>>  #include <linux/pm.h>
>> -#include <linux/uuid.h>
>>  
>>  #include "i2c-hid.h"
>>  
>>  struct i2c_hid_acpi {
>>  	struct i2chid_ops ops;
>> +	struct i2c_client *client;
>>  	struct acpi_device *adev;
>>  };
>>  
>> @@ -48,36 +48,11 @@ static const struct acpi_device_id i2c_hid_acpi_blacklist[] = {
>>  	{ }
>>  };
>>  
>> -/* HID I²C Device: 3cdff6f7-4267-4555-ad05-b30a3d8938de */
>> -static guid_t i2c_hid_guid =
>> -	GUID_INIT(0x3CDFF6F7, 0x4267, 0x4555,
>> -		  0xAD, 0x05, 0xB3, 0x0A, 0x3D, 0x89, 0x38, 0xDE);
>> -
>> -static int i2c_hid_acpi_get_descriptor(struct i2c_hid_acpi *ihid_acpi)
>> -{
>> -	struct acpi_device *adev = ihid_acpi->adev;
>> -	acpi_handle handle = acpi_device_handle(adev);
>> -	union acpi_object *obj;
>> -	u16 hid_descriptor_address;
>> -
>> -	obj = acpi_evaluate_dsm_typed(handle, &i2c_hid_guid, 1, 1, NULL,
>> -				      ACPI_TYPE_INTEGER);
>> -	if (!obj) {
>> -		acpi_handle_err(handle, "Error _DSM call to get HID descriptor address failed\n");
>> -		return -ENODEV;
>> -	}
>> -
>> -	hid_descriptor_address = obj->integer.value;
>> -	ACPI_FREE(obj);
>> -
>> -	return hid_descriptor_address;
>> -}
>> -
>>  static void i2c_hid_acpi_restore_sequence(struct i2chid_ops *ops)
>>  {
>>  	struct i2c_hid_acpi *ihid_acpi = container_of(ops, struct i2c_hid_acpi, ops);
>>  
>> -	i2c_hid_acpi_get_descriptor(ihid_acpi);
>> +	i2c_hid_core_acpi_get_descriptor(&ihid_acpi->client->dev);
>>  }
>>  
>>  static void i2c_hid_acpi_shutdown_tail(struct i2chid_ops *ops)
>> @@ -102,11 +77,12 @@ static int i2c_hid_acpi_probe(struct i2c_client *client)
>>  	if (!ihid_acpi)
>>  		return -ENOMEM;
>>  
>> +	ihid_acpi->client = client;
>>  	ihid_acpi->adev = adev;
>>  	ihid_acpi->ops.shutdown_tail = i2c_hid_acpi_shutdown_tail;
>>  	ihid_acpi->ops.restore_sequence = i2c_hid_acpi_restore_sequence;
>>  
>> -	ret = i2c_hid_acpi_get_descriptor(ihid_acpi);
>> +	ret = i2c_hid_core_acpi_get_descriptor(dev);
>>  	if (ret < 0)
>>  		return ret;
>>  	hid_descriptor_address = ret;
>> diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
>> index 3adb16366e93..1e1a8df5686d 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid-core.c
>> +++ b/drivers/hid/i2c-hid/i2c-hid-core.c
>> @@ -1405,6 +1405,41 @@ const struct dev_pm_ops i2c_hid_core_pm = {
>>  };
>>  EXPORT_SYMBOL_GPL(i2c_hid_core_pm);
>>  
>> +#ifdef CONFIG_ACPI
>> +#include <linux/acpi.h>
>> +
>> +/* HID I²C Device: 3cdff6f7-4267-4555-ad05-b30a3d8938de */
>> +static guid_t i2c_hid_guid =
>> +	GUID_INIT(0x3CDFF6F7, 0x4267, 0x4555,
>> +		  0xAD, 0x05, 0xB3, 0x0A, 0x3D, 0x89, 0x38, 0xDE);
>> +
>> +int i2c_hid_core_acpi_get_descriptor(struct device *dev)
>> +{
>> +	struct acpi_device *adev = ACPI_COMPANION(dev);
>> +	acpi_handle handle;
>> +	union acpi_object *obj;
>> +	u16 hid_descriptor_address;
>> +
>> +	if (!adev)
>> +		return -ENODEV;
>> +
>> +	handle = acpi_device_handle(adev);
>> +	obj = acpi_evaluate_dsm_typed(handle, &i2c_hid_guid, 1, 1, NULL,
>> +				      ACPI_TYPE_INTEGER);
>> +	if (!obj) {
>> +		acpi_handle_err(handle,
>> +				"Error _DSM call to get HID descriptor address failed\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	hid_descriptor_address = obj->integer.value;
>> +	ACPI_FREE(obj);
>> +
>> +	return hid_descriptor_address;
>> +}
>> +EXPORT_SYMBOL_GPL(i2c_hid_core_acpi_get_descriptor);
>> +#endif
>> +
>>  MODULE_DESCRIPTION("HID over I2C core driver");
>>  MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
>>  MODULE_LICENSE("GPL");
>> diff --git a/drivers/hid/i2c-hid/i2c-hid.h b/drivers/hid/i2c-hid/i2c-hid.h
>> index 1724a435c783..bc8661c65b1a 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid.h
>> +++ b/drivers/hid/i2c-hid/i2c-hid.h
>> @@ -44,4 +44,15 @@ void i2c_hid_core_shutdown(struct i2c_client *client);
>>  
>>  extern const struct dev_pm_ops i2c_hid_core_pm;
>>  
>> +#ifdef CONFIG_ACPI
>> +struct device;
>> +int i2c_hid_core_acpi_get_descriptor(struct device *dev);
>> +#else
>> +struct device;
>> +static inline int i2c_hid_core_acpi_get_descriptor(struct device *dev)
>> +{
>> +	return -ENODEV;
>> +}
>> +#endif
>> +
>>  #endif
>> -- 
>> 2.54.0
>>
>>