Re: [PATCH v3 1/3] HID: i2c-hid: Rely on HID descriptor fetch to probe

Kenny Levinsen
2024-05-01T23:09:44Z

On 5/1/24 9:09 PM, Dmitry Torokhov wrote:
> Is it possible for a device to be wedged so hard that it refuses to
> acknowledge the address?

A slave is allowed to not acknowledge if not able (e.g., "because it's
performing some real time function"), but a slave that does not
acknowledge its address is electrically indistinguishable from a
disconnected device. In such case the device is impossible to detect
through I2C operations, and neither smbus probe nor a "real" command
will see it.

Any logic we have to silence missing devices will also silence entirely
unresponsive or extremely non-cooperate devices. That is the price to
pay for avoiding the log message unfortunately.

No other errors from the smbus probe or a real command would be related
to device presence, and some of them even suggest a device is present
but broken (arbitration loss, assuming no shorts).