Hi again,
I realized I did not answer 1 of your questions:
On 17-08-17 21:39, Wolfram Sang wrote:
Hey guys,
Sorry, I don't understand some of the stuff here. But I'd like to
understand it before I add something to the I2C core. Especially as it
feels a bit a the edge of the driver model to me.
On Sat, Jul 22, 2017 at 08:55:37PM +0200, Hans de Goede wrote:
The CHPN0001 ACPI device has a _CID of PNP0C50 but is not HID compatible,
it uses its own protocol which is handled by the chipone_icn8318 driver.
If the i2c_hid_driver's probe functon gets called it will fail with a
"hid_descr_cmd failed" error.
That sounds like it fails pretty late. I'd assume we could check the
blacklist right at the beginning of probe and bail out immediately?
Worse, after the probe failure the i2c / ACPI core code will put the ACPI
device in D3 state
Where does that happen? Sorry, I can't find it. Would it be an idea to
add a flag somewhere telling the device should not be put into D3?
It is already possible to do this and my patches for the icn8318 driver
do this:
struct acpi_device *adev;
adev = ACPI_COMPANION(dev);
/*
* Disable ACPI power management the _PS3 method is empty, so
* there is no powersaving when using ACPI power management.
* The _PS0 method resets the controller causing it to loose its
* firmware, which has been loaded by the BIOS and we do not
* know how to restore the firmware.
*/
adev->flags.power_manageable = 0;
The problem is that this happens in the probe() from the icn8318 driver
and if the i2c-hid drivers probe() executes first we end up in the
dev_pm_domain_detach() path of i2c_device_probe() and after that the
touchscreen-controller no longer works (*), iow after that it is too late
to disable acpi pm for the device.
*) Unless we find a way to reload the firmware, which technically is
doable, but then we get into the problem of now having to distribute the
firmware in linux-firmware
Regards,
Hans
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