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ACPI: PNP: compare the string length in the matching_id() 

commit b08221c40f upstream.

Recently we met a touchscreen problem on some Thinkpad machines, the
touchscreen driver (i2c-hid) is not loaded and the touchscreen can't
work.

An i2c ACPI device with the name WACF2200 is defined in the BIOS, with
the current rule in matching_id(), this device will be regarded as
a PNP device since there is WACFXXX in the acpi_pnp_device_ids[] and
this PNP device is attached to the acpi device as the 1st
physical_node, this will make the i2c bus match fail when i2c bus
calls acpi_companion_match() to match the acpi_id_table in the i2c-hid
driver.

WACF2200 is an i2c device instead of a PNP device, after adding the
string length comparing, the matching_id() will return false when
matching WACF2200 and WACFXXX, and it is reasonable to compare the
string length when matching two IDs.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Hui Wang 2020-12-11 10:18:14 +08:00 committed by Greg Kroah-Hartman
parent 772dd826a4
commit 2c6c6001d0
1 changed files with 3 additions and 0 deletions
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3
drivers/acpi/acpi_pnp.c
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@ -317,6 +317,9 @@ static bool matching_id(const char *idstr, const char *list_id)
{
int i;
if (strlen(idstr) != strlen(list_id))
return false;
if (memcmp(idstr, list_id, 3))
return false;