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

From: Kenny Levinsen
Date: Wed May 01 2024 - 19:09:54 EST


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).