From: Kenny Levinsen <kl@kl.wtf>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Jiri Kosina <jikos@kernel.org>,
Dmitry Torokhov <dtor@chromium.org>,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
Douglas Anderson <dianders@chromium.org>,
Hans de Goede <hdegoede@redhat.com>,
Maxime Ripard <mripard@kernel.org>,
Kai-Heng Feng <kai.heng.feng@canonical.com>,
Johan Hovold <johan+linaro@kernel.org>,
linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
Radoslaw Biernacki <rad@chromium.org>,
Lukasz Majczak <lma@chromium.org>
Subject: Re: [PATCH v3 1/3] HID: i2c-hid: Rely on HID descriptor fetch to probe
Date: Thu, 2 May 2024 01:09:37 +0200 [thread overview]
Message-ID: <e85237b8-a572-4e45-aa08-18710635eea5@kl.wtf> (raw)
In-Reply-To: <ZjKTXaBrb1vs4har@google.com>
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).
next prev parent reply other threads:[~2024-05-01 23:09 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-26 22:47 [PATCH v3 0/3] HID: i2c-hid: Probe and wake device with HID descriptor fetch Kenny Levinsen
2024-04-26 22:47 ` [PATCH v3 1/3] HID: i2c-hid: Rely on HID descriptor fetch to probe Kenny Levinsen
2024-04-27 3:21 ` Dmitry Torokhov
2024-04-27 13:20 ` Kenny Levinsen
2024-04-30 21:41 ` Dmitry Torokhov
2024-05-01 5:24 ` Kenny Levinsen
2024-05-01 19:09 ` Dmitry Torokhov
2024-05-01 23:09 ` Kenny Levinsen [this message]
2024-04-26 22:47 ` [PATCH v3 2/3] HID: i2c-hid: Retry HID descriptor read to wake up STM devices Kenny Levinsen
2024-04-26 22:47 ` [PATCH v3 3/3] HID: i2c-hid: Align i2c_hid_set_power() retry with HID descriptor read Kenny Levinsen
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