This is a note to let you know that I've just added the patch titled
HID: i2c-hid: Revert to await reset ACK before reading report descriptor
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
hid-i2c-hid-revert-to-await-reset-ack-before-reading-report-descriptor.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ea36bf1827462e4a52365bf8e3f7d1712c5d9600 Mon Sep 17 00:00:00 2001
From: Kenny Levinsen <kl@xxxxxx>
Date: Tue, 2 Apr 2024 13:10:04 +0200
Subject: HID: i2c-hid: Revert to await reset ACK before reading report descriptor
From: Kenny Levinsen <kl@xxxxxx>
commit ea36bf1827462e4a52365bf8e3f7d1712c5d9600 upstream.
In af93a167eda9, i2c_hid_parse was changed to continue with reading the
report descriptor before waiting for reset to be acknowledged.
This has lead to two regressions:
1. We fail to handle reset acknowledgment if it happens while reading
the report descriptor. The transfer sets I2C_HID_READ_PENDING, which
causes the IRQ handler to return without doing anything.
This affects both a Wacom touchscreen and a Sensel touchpad.
2. On a Sensel touchpad, reading the report descriptor this quickly
after reset results in all zeroes or partial zeroes.
The issues were observed on the Lenovo Thinkpad Z16 Gen 2.
The change in question was made based on a Microsoft article[0] stating
that Windows 8 *may* read the report descriptor in parallel with
awaiting reset acknowledgment, intended as a slight reset performance
optimization. Perhaps they only do this if reset is not completing
quickly enough for their tastes?
As the code is not currently ready to read registers in parallel with a
pending reset acknowledgment, and as reading quickly breaks the report
descriptor on the Sensel touchpad, revert to waiting for reset
acknowledgment before proceeding to read the report descriptor.
[0]: https://learn.microsoft.com/en-us/windows-hardware/drivers/hid/plug-and-play-support-and-power-management
Fixes: af93a167eda9 ("HID: i2c-hid: Move i2c_hid_finish_hwreset() to after reading the report-descriptor")
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2271136
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Kenny Levinsen <kl@xxxxxx>
Link: https://lore.kernel.org/r/20240331182440.14477-1-kl@xxxxxx
[hdegoede@xxxxxxxxxx Drop no longer necessary abort_reset error exit path]
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Tested-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/hid/i2c-hid/i2c-hid-core.c | 29 ++++++++---------------------
1 file changed, 8 insertions(+), 21 deletions(-)
diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index 1c86c97688e9..d965382196c6 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -726,12 +726,15 @@ static int i2c_hid_parse(struct hid_device *hid)
mutex_lock(&ihid->reset_lock);
do {
ret = i2c_hid_start_hwreset(ihid);
- if (ret)
+ if (ret == 0)
+ ret = i2c_hid_finish_hwreset(ihid);
+ else
msleep(1000);
} while (tries-- > 0 && ret);
+ mutex_unlock(&ihid->reset_lock);
if (ret)
- goto abort_reset;
+ return ret;
use_override = i2c_hid_get_dmi_hid_report_desc_override(client->name,
&rsize);
@@ -741,11 +744,8 @@ static int i2c_hid_parse(struct hid_device *hid)
i2c_hid_dbg(ihid, "Using a HID report descriptor override\n");
} else {
rdesc = kzalloc(rsize, GFP_KERNEL);
-
- if (!rdesc) {
- ret = -ENOMEM;
- goto abort_reset;
- }
+ if (!rdesc)
+ return -ENOMEM;
i2c_hid_dbg(ihid, "asking HID report descriptor\n");
@@ -754,23 +754,10 @@ static int i2c_hid_parse(struct hid_device *hid)
rdesc, rsize);
if (ret) {
hid_err(hid, "reading report descriptor failed\n");
- goto abort_reset;
+ goto out;
}
}
- /*
- * Windows directly reads the report-descriptor after sending reset
- * and then waits for resets completion afterwards. Some touchpads
- * actually wait for the report-descriptor to be read before signalling
- * reset completion.
- */
- ret = i2c_hid_finish_hwreset(ihid);
-abort_reset:
- clear_bit(I2C_HID_RESET_PENDING, &ihid->flags);
- mutex_unlock(&ihid->reset_lock);
- if (ret)
- goto out;
-
i2c_hid_dbg(ihid, "Report Descriptor: %*ph\n", rsize, rdesc);
ret = hid_parse_report(hid, rdesc, rsize);
--
2.44.0
Patches currently in stable-queue which might be from kl@xxxxxx are
queue-6.8/hid-i2c-hid-revert-to-await-reset-ack-before-reading-report-descriptor.patch
