Re: [PATCH] i2c: acpi: Force Dell XPS 17 9720 touchpad to 100 kHz

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Fri, Nov 13, 2026 at 10:52:09AM +0100, Hans de Goede wrote:
> Hi,
> 
> On 13-Nov-26 09:39, Mika Westerberg wrote:
> > The Dell XPS 17 9720 touchpad has the same lagging issue as with others
> > when run at 400 kHz as the ACPI tables describe. This particular system
> > does not use standard ACPI ID but it seems to use "Windows Device ID"
> > VEN_04F3 for whatever reason. Add this one to the 100 kHz quirk list as
> > well but since this is not a standard ACPI ID match it also via DMI
> > strings just to be on the safe side.
> > 
> > Reported-by: penhouse24@proton.me
> > Link: https://lore.kernel.org/linux-i2c/20261109104542.GL176724@black.igk.intel.com/
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> 
> Thank you for your patch.
> 
> > ---
> >  drivers/i2c/i2c-core-acpi.c | 24 +++++++++++++++++++++++-
> >  1 file changed, 23 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
> > index 84841ed13487..98a8d63e3fb8 100644
> > --- a/drivers/i2c/i2c-core-acpi.c
> > +++ b/drivers/i2c/i2c-core-acpi.c
> > @@ -7,6 +7,7 @@
> >  
> >  #include <linux/acpi.h>
> >  #include <linux/device.h>
> > +#include <linux/dmi.h>
> >  #include <linux/err.h>
> >  #include <linux/i2c.h>
> >  #include <linux/list.h>
> > @@ -356,6 +357,16 @@ static const struct acpi_device_id i2c_acpi_force_400khz_device_ids[] = {
> >  	{ }
> >  };
> >  
> > +static const struct dmi_system_id i2c_acpi_dell_xps_17_9720_dmi_ids[] = {
> > +	{
> > +		.matches = {
> > +			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
> > +			DMI_MATCH(DMI_PRODUCT_NAME, "XPS 17 9720"),
> > +		},
> > +	},
> > +	{ }
> > +};
> > +
> >  static const struct acpi_device_id i2c_acpi_force_100khz_device_ids[] = {
> >  	/*
> >  	 * When a 400KHz freq is used on this model of ELAN touchpad in Linux,
> > @@ -377,6 +388,14 @@ static const struct acpi_device_id i2c_acpi_force_100khz_device_ids[] = {
> >  	{ .id = "ELAN0678" },
> >  	{ .id = "ELAN06FA" },
> >  	{ .id = "ELAN1300" },
> > +	{
> > +		/*
> > +		 * Some Dell XPS 17 9720 systems do not use standard
> > +		 * ACPI IDs so we need to match also via DMI strings.
> > +		 */
> > +		.id = "VEN_04F3",
> 
> 04F3 is ELAN's USB/I2C-HID vendor ID and the commonality between all touchpads
> with needs this seems to be them being from ELAN.
> 
> Also a quick grep through my DSDT collection shows 0 uses of VEN_04F3,
> which makes me think this is pretty unique.
> 
> So all in all I think we can just add a match on "VEN_04F3" without
> requiring / adding DMI matching ?

Works for me. I'll do that in v2.