On Wed, May 5, 2021 at 4:00 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>
> Hi,
>
> On 5/5/21 3:40 PM, Benjamin Tissoires wrote:
> > Hi Hans,
> >
> > On Sat, Mar 6, 2021 at 2:37 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> >>
> >> Disable event reporting on suspend when our parent is not
> >> a wakeup-source. This should help save some extra power in
> >> this case.
> >>
> >> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> >> ---
> >> drivers/hid/Kconfig | 2 +-
> >> drivers/hid/hid-multitouch.c | 23 ++++++++++++++++++++++-
> >> 2 files changed, 23 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
> >> index 786b71ef7738..5cbe4adfd816 100644
> >> --- a/drivers/hid/Kconfig
> >> +++ b/drivers/hid/Kconfig
> >> @@ -675,7 +675,7 @@ config HID_MONTEREY
> >>
> >> config HID_MULTITOUCH
> >> tristate "HID Multitouch panels"
> >> - depends on HID
> >> + depends on USB_HID
> >
> > I tried really hard during the past 8 years to not have a usbhid
> > dependency on hid-multitouch.
> >
> > The code below should not break the test suite, but still I am not
> > that happy about the Kconfig change.
> >
> > I don't see an immediate and better way of doing what you are
> > achieving here, but maybe you have some magic I did not think about
> > that would help to no pull USB_HID with HID_MULTITOUCH.
> >
> > FTR, I think the use case of hid-multitouch *without* USB is rather
> > non-existent, but there might be some weird systems with I2C only
> > (edge computing?).
>
> Interesting how you often manage to pick out the bits of patches
> which I'm not 100% happy with myself either. I was thinking the
> same thing myself.
:)
>
> We have this: "hid_is_using_ll_driver(hdev, &usb_hid_driver)" check
> in various drivers under drivers/hid and so far the dependency fix
> of adding a "depends on USB_HID" was not pretty but ok, because it
> would be weird to enable those HID drivers on a system without
> USB_HID being enabled. But I agree with you that hid-multitouch
> is different. So I did try to come up with something better and
> failed.
>
> But now that I look at this with fresh eyes I think I see a
> nice solution for this.
>
> I propose to add a hid_is_usb_device() helper which is defined
> in hid-core.c (1) and this helper would look like this:
>
> bool hid_is_usb_device(struct hid_device *hid)
> {
> #if IS_ENABLED(CONFIG_USB_HID)
> return hid_is_using_ll_driver(hid, &usb_hid_driver);
> #else
> return false;
> #endif
> }
>
> And then I can use this helper function instead of directly doing
> the hid_is_using_ll_driver() check in hid-multitouch.c fixing
> this dependency ugliness.
>
> 1) hid-core.c is controlled by CONFIG_HID which gets selected at
> the Kconfig level by CONFIG_USB_HID so there is no chance of
> builtin vs module issues.
OK, sounds good enough to me. The one thing I dislike about IS_ENABLED
is that it is not very friendly with out of the tree modules. But
here, I guess if you have a system without CONFIG_USB_HID, you will
probably never need to enable it without recompiling your tree.
So ack by me.
>
> As an added bonus I can then also do a follow-up patch-set to
> remove more depends on USB_HID stuff by switching to the helper
> in other places too.
That would be wonderful :)
>
> ###
>
> Unrelated but something else which I was wondering about while
> working on this patch.
>
> I think that it might also be useful to change the
> mt_parent_may_wake() helper introduced here into a generic
> hid_parent_may_wakeup() helper in case we need a similar thing
> in other places. I decided it may be best to do that once we
> have a second driver needing such a check, but since we're
> discussing this anyways, what is your opinion on this ?
I can definitely see the benefit of it, but OTOH, I would stick to
your first approach. If we are just needing it for one driver, we
probably want to keep it local to this one driver.
Cheers,
Benjamin
>
> Regards,
>
> Hans
>
>
>
> >> help
> >> Generic support for HID multitouch panels.
> >>
> >> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> >> index cfb68e443ddd..7926295bab81 100644
> >> --- a/drivers/hid/hid-multitouch.c
> >> +++ b/drivers/hid/hid-multitouch.c
> >> @@ -1759,12 +1759,33 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
> >> }
> >>
> >> #ifdef CONFIG_PM
> >> +
> >> +/* Check if the parent which has the power/wakeup* sysfs attributes may wake the hdev */
> >> +static bool mt_parent_may_wake(struct hid_device *hdev)
> >> +{
> >> + struct device *parent = hdev->dev.parent;
> >> +
> >> + /*
> >> + * USB-HID is attached to the usb_interface (our parent), the
> >> + * power/wakeup* attr are part of the usb-device which is its parent.
> >> + */
> >> + if (hid_is_using_ll_driver(hdev, &usb_hid_driver) && parent)
> >> + parent = parent->parent;
> >> +
> >> + if (parent)
> >> + return device_may_wakeup(parent);
> >> +
> >> + /* Huh? Play it safe and keep reporting events. */
> >> + return true;
> >> +}
> >> +
> >> static int mt_suspend(struct hid_device *hdev, pm_message_t state)
> >> {
> >> struct mt_device *td = hid_get_drvdata(hdev);
> >>
> >> /* High latency is desirable for power savings during S3/S0ix */
> >> - if (td->mtclass.quirks & MT_QUIRK_DISABLE_WAKEUP)
> >> + if ((td->mtclass.quirks & MT_QUIRK_DISABLE_WAKEUP) ||
> >> + !mt_parent_may_wake(hdev))
> >> mt_set_modes(hdev, HID_LATENCY_HIGH, false, false);
> >> else
> >> mt_set_modes(hdev, HID_LATENCY_HIGH, true, true);
> >> --
> >> 2.30.1
> >>
> >
>
