linux-kernel - Re: [PATCH] HID: rmi: Check that a device is a RMI device before calling RMI functions

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Message-ID: <37d50592-39b6-680f-6d02-1a7daa9a9208@synaptics.com>
Date:   Wed, 18 Oct 2017 10:28:45 -0700
From:   Andrew Duggan <aduggan@...aptics.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hendrik Langer <hendrik.langer@....de>
Subject: Re: [PATCH] HID: rmi: Check that a device is a RMI device before
 calling RMI functions



On 10/18/2017 07:13 AM, Jiri Kosina wrote:
> On Wed, 18 Oct 2017, Benjamin Tissoires wrote:
>
>>> The hid-rmi driver may handle non rmi devices on composite USB devices.
>>> Callbacks need to make sure that the current device is a RMI device before
>>> calling RMI specific functions. Most callbacks already have this check, but
>>> this patch adds checks to the remaining callbacks.
>>>
>>> Signed-off-by: Andrew Duggan <aduggan@...aptics.com>
>>> ---
>>> This is the patch which hopefully will address the X1 tablet dock freeze:
>>> http://www.spinics.net/lists/linux-input/msg53582.html
>>>
>>> I was not able to test on a composite USB device so I have not tested confirmed
>>> this will fix the reported issues. But, based on the description I think it will.
>>> I also added a check for rmi_raw_event() since it could be possible that another
>>> hid device using one of the same report IDs as an RMI device could result in calling
>>> into unitialized RMI functions. It was also the only callbacl left not checking the
>>> RMI_DEVICE flag. I wonder if this explains the attach crash.
>>>
>>> Anyway, I would appriciate it if Hendrik or someone else with the device could test this
>>> patch to confirm it fixes the reported behavior.
>> Shouldn't rmi_hid_reset() also get the same check?
> I think so as well.

Since rmi_hid_reset() is only called from with in the RMI4 driver I 
didn't think that it needed a check. All of the functions set in struct 
hid_driver should  now check the RMI_DEVICE flag before calling into the 
RMI4 driver. But, if I am missing something we can add additional checks.

Thanks,
Andrew

>>  From what I can see, even if the patch doesn't fix the immediate issue,
>> such a patch should definitively go in as those checks are clearly
>> missing.
> Agreed; however I'd like to get Hendrik's Tested-by: if possible in case
> this really fixes the issue, so I am not merging it right away.
>
> Hendrik, are you by any chance able to test this patch in a reasonable
> timeframe please?
>
> Thanks!
>