linux-kernel - Re: [PATCH] HID: logitech-dj: add HIDRAW dependency in Kconfig

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Date:	Tue, 3 Dec 2013 15:03:52 +0100
From:	Nestor Lopez Casado <nlopezcasad@...itech.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Olivier Gay <ogay@...itech.com>,
	"open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mathieu Meisser <mmeisser@...itech.com>
Subject: Re: [PATCH] HID: logitech-dj: add HIDRAW dependency in Kconfig

Sorry, no html now.


On Tue, Dec 3, 2013 at 3:01 PM, Nestor Lopez Casado
<nlopezcasad@...itech.com> wrote:
>
>
>
>
> On Tue, Dec 3, 2013 at 1:51 PM, Jiri Kosina <jkosina@...e.cz> wrote:
>>
>> On Tue, 3 Dec 2013, Olivier Gay wrote:
>>
>> > Without hidraw driver, we get this:
>> >
>> > <3>[  210.131988] logitech-djreceiver 0003:046D:C52B.0005: claimed by
>> > neither input, hiddev nor hidraw
>> > <3>[  210.132202] logitech-djreceiver 0003:046D:C52B.0005:
>> > logi_dj_probe:hid_hw_start returned error
>> >
>> > In logi_dj_probe, we call hid_hw_start with HID_CONNECT_DEFAULT
>> > argument and if hidraw driver is not present, the call fails and we
>> > return an error in logi_dj_probe.
>> >
>> > > It's clear that without hidraw it's not possible to change the pairing
>> > > from userspace, but I fail to see why probing the receiver should be
>> > > affected?
>> >
>> > As of today, hid-logitech-dj.c depends on hidraw API to work. All HID
>> > reports sent to control / configure the receiver are sent using hidraw
>> > API. That's why we fail logi_dj_probe if we cannot connect to hidraw.
>>
>> Hmm, so unifying receiver is not claimed by hid-input at all?
>> (HID_CONNECT_DEFAULT also contains HID_CONNECT_HIDINPUT) How so?
>>
>> (again, I will not be able to test it with my receiver up until the day
>> after tomorrow).
>
> The unifying receiver has 3 usb interfaces. When hid-logitech-dj driver is loaded, interfaces 0 and 1 are discarded.
>
> Interface 2 consists of a hid class interface with 3 collections, each of which sports the 'vendor' usage, thus, there is no reason for hid_input to claim any of them. On the other hand, hidraw has no issue in claiming the collections, even if they are 'vendor'. As of today, hid-logitech-dj uses hidraw api to send configuration/control reports to interface 2 of the Unifying receiver.
>
> Without the hid-logitech-dj driver, interfaces 0 and 1 are claimed by hid-input, as they correspond to a keyboard and a mouse. But that is not relevant to the discussion.
>>
>>
>> Thanks,
>>
>> --
>> Jiri Kosina
>> SUSE Labs
>
> Cheers,
> -nestor
>
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