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Message-ID: <4e846cf1-e7c7-3bb9-d8b3-d266b9dfbc4e@linux.intel.com>
Date: Thu, 26 Jun 2025 18:09:47 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Vishnu Sankar <vishnuocv@...il.com>
cc: pali@...nel.org, dmitry.torokhov@...il.com, hmh@....eng.br,
hansg@...nel.org, tglx@...utronix.de, mingo@...nel.org, jon_xie@...art.com,
jay_lee@...art.com, zhoubinbin@...ngson.cn, linux-input@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>, ibm-acpi-devel@...ts.sourceforge.net,
platform-driver-x86@...r.kernel.org, vsankar@...ovo.com,
Mark Pearson <mpearson-lenovo@...ebb.ca>
Subject: Re: [PATCH] x86/Mouse: thinkpad_acpi/Trackpoint: Trackpoint Doubletap
handling
On Thu, 26 Jun 2025, Vishnu Sankar wrote:
> Hi Ilpo,
>
> Thanks a lot for the comments and guidance.
> Please find my comments inline below.
>
> On Wed, Jun 25, 2025 at 9:07 PM Ilpo Järvinen < ilpo.jarvinen@...ux.intel.com >
> wrote:
> On Fri, 20 Jun 2025, Vishnu Sankar wrote:
>
> I don't like the shortlog prefixes (in the subject), please don't make
> confusing prefixes up like that.
>
> Got it.
> I will correct this in V2 (as a patch series).
>
> > Newer ThinkPads have a doubletap feature that needs to be turned
> > ON/OFF via the trackpoint registers.
>
> Don't leave lines short mid-paragraph. Either reflow the paragraph or add
> an empty line in between paragraphs.
>
> Acked.
> Will correct this in V2.
>
> > Systems released from 2023 have doubletap disabled by default and
> > need the feature enabling to be useful.
> >
> > This patch introduces support for exposing and controlling the
> > trackpoint doubletap feature via a sysfs attribute.
> > /sys/devices/platform/thinkpad_acpi/tp_doubletap
> > This can be toggled by an "enable" or a "disable".
>
> This too has too short lines.
>
> Sorry!
> Will do the needful in v2.
>
> >
> > With this implemented we can remove the masking of events, and rely on
>
> "With this implemented" is way too vague wording.
>
> Sorry for this!
> I will make this better.
>
> > HW control instead, when the feature is disabled.
> >
> > Note - Early Thinkpads (pre 2015) used the same register for hysteris
>
> hysteresis ?
>
> Sorry for not being clear.
> It's the trackpoint drag hysteris functionality. Pre-2015 ThinkPads used to have a
> user-configurable drag hysterisis register (0x58).
> Drag hysterisis is not user configurable now.
>
> > control, Check the FW IDs to make sure these are not affected.
>
> This Note feels very much disconnected from the rest. Should be properly
> described and perhaps in own patch (I don't know)?
>
> my bad, it's not FW ID, but PnP ID.
> The older ThinkPad's trackpoint controllers use the same register (0x58) to control
> the drag hysteresis, which is obsolete now.
> Now (on newer systems from 2023) the same register (0x58) is remapped as
> doubletap register.
> Just to exclude those older systems (with drag hysterisis control), we check the PnP
> ID's.
>
> I will give a better commit message in V2.
>
> > trackpoint.h is moved to linux/input/.
>
> This patch doesn't look minimal and seems to be combining many changes
> into one. Please make a patch series out of changes that can be separated
> instead of putting all together.
>
> Understood.
> Will make a patch series on V2
> 0001: Move trackpoint.h to include/linux/input
> 0002: Add new doubletap set/status/capable logics to trackpoint.c
> 0003: Add new trackpoint api's and trackpoint sysfs in thinkpad_acpi.c
Okay, sounds better.
> > +/* List of known incapable device PNP IDs */
> > +static const char * const dt_incompatible_devices[] = {
> > + "LEN0304",
> > + "LEN0306",
> > + "LEN0317",
> > + "LEN031A",
> > + "LEN031B",
> > + "LEN031C",
> > + "LEN031D",
> > +};
> > +
> > +/*
> > + * checks if it’s a doubletap capable device
> > + * The PNP ID format eg: is "PNP: LEN030d PNP0f13".
> > + */
> > +bool is_trackpoint_dt_capable(const char *pnp_id)
> > +{
> > + char id[16];
> > +
> > + /* Make sure string starts with "PNP: " */
> > + if (strncmp(pnp_id, "PNP: LEN03", 10) != 0)
>
> We seem to have strstarts().
>
> Thanks a lot for the suggestion.
> Will make use of this.
>
> > + return false;
> > +
> > + /* Extract the first word after "PNP: " */
> > + if (sscanf(pnp_id + 5, "%15s", id) != 1)
> > + return false;
> > +
> > + /* Check if it's blacklisted */
> > + for (size_t i = 0; i < ARRAY_SIZE(dt_incompatible_devices); ++i)
> {
> > + if (strcmp(pnp_id, dt_incompatible_devices[i]) == 0)
>
> Isn't this buggy wrt. the PNP: prefix??
>
> Perhaps it would have been better to just do pnp_id += 5 before sscanf()
> as you don't care about the prefix after that.
>
>
> Understood.
> Shall we have something like the following:
> if (!strstarts(pnp_id, "PNP: LEN03"))
> return false;
>
> id = pnp_id + 5;
>
> for (size_t i = 0; i < ARRAY_SIZE(dt_incompatible_devices); ++i) {
> if (strncmp(id, dt_incompatible_devices[i],
> strlen(dt_incompatible_devices[i])) == 0)
Why did you change to strncmp()?
> > + return sysfs_emit(buf, "%s\n", status ? "enabled" : "disabled");
>
> I'm sure there's an existing helper for this bool -> "enabled"/"disabled"
> conversion (make sure you add the #include if not yet there when you use
> the helper).
>
> Is "bool_to_enabled_disabled(status)" the one that you are referring to?
Please see linux/string_choices.h, but after you change the attribute
name, this won't be required as you can use normal boolean style with 0/1.
> > +}
> > +
> > +static ssize_t tp_doubletap_store(struct device *dev, struct
> device_attribute *attr, const char *buf, size_t count)
> > +{
> > + if (sysfs_streq(buf, "enable")) {
>
> Hmm, should this attribute be named doubletap_enabled and follow the
> usual
> boolean convention instead?
>
> Will change the attribute name as suggested.
Please also use kstrtobool() then to convert the value.
> > + /* enabling the doubletap here */
> > + if (!trackpoint_set_doubletap(true))
> > + tp_features.trackpoint_doubletap_state = true;
> > + } else if (sysfs_streq(buf, "disable")) {
> > + /* disabling the doubletap here */
> > + if (!trackpoint_set_doubletap(false))
> > + tp_features.trackpoint_doubletap_state = false;
> > + } else {
> > + pr_err("ThinkPad ACPI: thinkpad_acpi: Invalid value '%s'
> for tp_doubletap\n", buf);
>
> No, sysfs store function should not spam log like this, returning -EINVAL
> tells the very same thing already.
>
> Acked.
> will be removing the log.
>
> > + return -EINVAL;
> > + }
> > +
> > + return count;
> > +}
--
i.
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