From: Alan Stern <stern@rowland.harvard.edu>
To: Maxim Devaev <mdevaev@gmail.com>
Cc: balbi@kernel.org, gregkh@linuxfoundation.org,
ruslan.bilovol@gmail.com, mika.westerberg@linux.intel.com,
maze@google.com, jj251510319013@gmail.com,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: gadget: f_hid: optional SETUP/SET_REPORT mode
Date: Fri, 13 Aug 2021 21:45:18 -0400 [thread overview]
Message-ID: <20210814014518.GA56183@rowland.harvard.edu> (raw)
In-Reply-To: <20210813234022.5d5644ae@reki>
On Fri, Aug 13, 2021 at 11:40:22PM +0300, Maxim Devaev wrote:
> В Fri, 13 Aug 2021 23:22:12 +0300
> Maxim Devaev <mdevaev@gmail.com> пишет:
>
> > Alan Stern <stern@rowland.harvard.edu> wrote:
> > > In other words, a device does not need to have an interrupt-OUT
> > > endpoint, but if it does have one then the host must use it.
> >
> > You're right. Although the actual behavior of the hosts is not different
> > from what I wrote - they really just ignore out endpoint.
> > I will eventually fix this in the patch description.
>
> It seems that I have confused everything even more, sorry. I will explain.
> There are three possible host behaviors:
>
> (1) The host works with the OUT endpoint as it describes the standard
> and transmits reports through it.
>
> (2) The host works with IN endpoint, but refuses to transmit reports
> via OUT endpoint at all. In the case of the keyboard, it will work,
> but it will not receive the status of the LEDs.
>
> (3) The host sees OUT endpoint and either refuses to use such a device at all,
> or goes crazy in various ways.
>
> In both cases (2) and (3), using SETUP/SET_REPORT solves the problem.
> Therefore, I offer this as an option to solve compatibility problems.
> Yes, in fact, this is not our problem, but it is impossible to fix the drivers
> of all these proprietary devices. Moreover, I have never met a keyboard
> with OUT endpoint, absolutely all of them use SETUP/SET_REPORT.
Okay. I appreciate the more detailed explanations; thanks. Please
resubmit the patch with appropriate changes to the description.
Alan Stern
prev parent reply other threads:[~2021-08-14 1:45 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-13 11:45 [PATCH] usb: gadget: f_hid: optional SETUP/SET_REPORT mode Maxim Devaev
2021-08-13 14:58 ` Alan Stern
2021-08-13 20:22 ` Maxim Devaev
2021-08-13 20:40 ` Maxim Devaev
2021-08-14 1:45 ` Alan Stern [this message]
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