Re: Re: [PATCH v6 2/5] HID: quirks: Refactor ELAN 400 and 401 handling

[Benjamin Tissoires <benjamin.tissoires@redhat.com>]

On Thu, Jun 13, 2019 at 12:20 AM Jeffrey Hugo <jhugo@codeaurora.org> wrote:
>
> On 6/12/2019 3:46 PM, Dmitry Torokhov wrote:
> > On Wed, Jun 12, 2019 at 02:27:21PM -0700, Jeffrey Hugo wrote:
> >> There needs to be coordination between hid-quirks and the elan_i2c driver
> >> about which devices are handled by what drivers.  Currently, both use
> >> whitelists, which results in valid devices being unhandled by default,
> >> when they should not be rejected by hid-quirks.  This is quickly becoming
> >> an issue.
> >>
> >> Since elan_i2c has a maintained whitelist of what devices it will handle,
> >> which is now in a header file that hid-quirks can access, use that to
> >> implement a blacklist in hid-quirks so that only the devices that need to
> >> be handled by elan_i2c get rejected by hid-quirks, and everything else is
> >> handled by default.
> >>
> >> Suggested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> >> Signed-off-by: Jeffrey Hugo <jeffrey.l.hugo@gmail.com>
> >> ---
> >>   drivers/hid/hid-quirks.c | 27 ++++++++++++++++-----------
> >>   1 file changed, 16 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/drivers/hid/hid-quirks.c b/drivers/hid/hid-quirks.c
> >> index e5ca6fe2ca57..bd81bb090222 100644
> >> --- a/drivers/hid/hid-quirks.c
> >> +++ b/drivers/hid/hid-quirks.c
> >> @@ -16,6 +16,7 @@
> >>   #include <linux/export.h>
> >>   #include <linux/slab.h>
> >>   #include <linux/mutex.h>
> >> +#include <linux/input/elan-i2c-ids.h>
> >>
> >>   #include "hid-ids.h"
> >>
> >> @@ -914,6 +915,8 @@ static const struct hid_device_id hid_mouse_ignore_list[] = {
> >>
> >>   bool hid_ignore(struct hid_device *hdev)
> >>   {
> >> +    int i;
> >> +
> >>      if (hdev->quirks & HID_QUIRK_NO_IGNORE)
> >>              return false;
> >>      if (hdev->quirks & HID_QUIRK_IGNORE)
> >> @@ -978,18 +981,20 @@ bool hid_ignore(struct hid_device *hdev)
> >>              break;
> >>      case USB_VENDOR_ID_ELAN:
> >>              /*
> >> -             * Many Elan devices have a product id of 0x0401 and are handled
> >> -             * by the elan_i2c input driver. But the ACPI HID ELAN0800 dev
> >> -             * is not (and cannot be) handled by that driver ->
> >> -             * Ignore all 0x0401 devs except for the ELAN0800 dev.
> >> +             * Blacklist of everything that gets handled by the elan_i2c
> >> +             * input driver.  This avoids disabling valid touchpads and
> >> +             * other ELAN devices.
> >>               */
> >> -            if (hdev->product == 0x0401 &&
> >> -                strncmp(hdev->name, "ELAN0800", 8) != 0)
> >> -                    return true;
> >> -            /* Same with product id 0x0400 */
> >> -            if (hdev->product == 0x0400 &&
> >> -                strncmp(hdev->name, "QTEC0001", 8) != 0)
> >> -                    return true;
> >> +            if ((hdev->product == 0x0401 || hdev->product == 0x0400)) {
> >> +                    for (i = 0; strlen(elan_acpi_id[i].id); ++i)
> >> +                            if (!strncmp(hdev->name, elan_acpi_id[i].id,
> >> +                                         strlen(elan_acpi_id[i].id)))
> >> +                                    return true;
> >> +                    for (i = 0; strlen(elan_of_match[i].name); ++i)
> >> +                            if (!strncmp(hdev->name, elan_of_match[i].name,
> >> +                                         strlen(elan_of_match[i].name)))
> >> +                                    return true;
> >
> > Do we really need to blacklist the OF case here? I thought that in ACPI
> > case we have clashes as HID gets matched by elan_i2c and CID is matched
> > by i2c-hid, but I do not believe we'll run into the same situation on OF
> > systems.
>
> I think its the safer approach.
>
> On an OF system, such as patch 3 in the series, the "hid-over-i2c" will
> end up running through this (kind of the whole reason why this series
> exists).  The vendor and product ids will still match, so we'll end up
> going through the lists to see if the hdev->name (the compatible string)
> will match the blacklist.  "hid-over-i2c" won't match the blacklist, but
> if there is a more specific compatible, it might.
>
> In that case, not matching OF would work, however how it could break
> today is if both "hid-over-i2c" and "elan,ekth3000" were listed for the
> same device, and elan_i2c was not compiled.  In that case, if we skip
> the OF part of the black list, hid-quirks will not reject the device,
> and you'll probably have some odd behavior instead of the obvious "the
> device doesn't work because the correct driver isn't present" behavior.
>
> While that scenario might be far fetched since having both
> "hid-over-i2c" and "elan,ekth3000" probably violates the OF bindings,
> its still safer to include the OF case in the blacklist against future
> scenarios.
>
>

Dmitry, if you are happy with Jeffrey's answer, feel free to take this
through your tree and add:
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

I don't expect any major conflicts given on where the code is located.

Cheers,
Benjamin