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

[Jeffrey Hugo <jhugo@codeaurora.org>]

On 6/13/2019 2:55 AM, Benjamin Tissoires wrote:
> 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.

Ping?

Dmitry, are you happy with things?  I would really like to see this 
queued for 5.3, and it seems like the window to do so is rapidly closing.