From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C420D13A244; Tue, 13 Aug 2024 08:38:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723538282; cv=none; b=jPzW7L/fqPq6KUnUsK3ivop+yUVY4b5f4OJFv6jkY2/2LVdfRpvp0xK83qtTLxTCTfCI5LJr9DtSlv016ewMbK8M40MQiBX2DQ3EAL+mgJFEY7MGea18Gsa00BgdhcBmgH0p3EzqTkjE3KxuVBGmeIEFycOyvzmggP7s7tLMuZQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723538282; c=relaxed/simple; bh=sZFZZlkis/Zz/vIzKVgMGqKTDYvtilTbLcStBns1FO0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=P7xHHwAlfzhE2JcDZMyifoYa1QQM6pN9zx+G9GUoBH4/w8KAn68kzh4Ci82TCUKomodjME5SSGQHx11u9AD/8e+Tb2y71EEl5jR+Hg/qQbt5LDSJsr5yoJDa9Wm+38v2L9OcbuPMenft9R3dEqdpXm8ao5elxoEFMQu79THmu1g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=m401v8ti; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="m401v8ti" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AEC22C4AF09; Tue, 13 Aug 2024 08:38:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1723538282; bh=sZFZZlkis/Zz/vIzKVgMGqKTDYvtilTbLcStBns1FO0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m401v8tiYHgPJncuC/qBhs+LGZYq9V23J0VBNZgiZ3v13Njcpfa04IevcpbVzqgAN nr7sU3qhPMHMmeugGlVosjfJ1yJJmvYhG/Oigbp/zu0mud0eg5fqvVh5V/DSAr9ouH VG2n876zBW8WkXVK/lTfaffJylnRYi7Je5txe438= Date: Tue, 13 Aug 2024 10:37:59 +0200 From: Greg Kroah-Hartman To: crwulff@gmail.com Cc: linux-usb@vger.kernel.org, Konstantin Aladyshev , David Sands , Jeff Johnson , Christophe JAILLET , linux-kernel@vger.kernel.org, Chris Wulff Subject: Re: [PATCH v3] USB: gadget: f_hid: Add GET_REPORT via userspace IOCTL Message-ID: <2024081345-emerald-subarctic-cb5f@gregkh> References: <20240810141834.640887-2-crwulff@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240810141834.640887-2-crwulff@gmail.com> On Sat, Aug 10, 2024 at 10:18:35AM -0400, crwulff@gmail.com wrote: > From: Chris Wulff > > While supporting GET_REPORT is a mandatory request per the HID > specification the current implementation of the GET_REPORT request responds > to the USB Host with an empty reply of the request length. However, some > USB Hosts will request the contents of feature reports via the GET_REPORT > request. In addition, some proprietary HID 'protocols' will expect > different data, for the same report ID, to be to become available in the > feature report by sending a preceding SET_REPORT to the USB Device that > defines what data is to be presented when that feature report is > subsequently retrieved via GET_REPORT (with a very fast < 5ms turn around > between the SET_REPORT and the GET_REPORT). > > There are two other patch sets already submitted for adding GET_REPORT > support. The first [1] allows for pre-priming a list of reports via IOCTLs > which then allows the USB Host to perform the request, with no further > userspace interaction possible during the GET_REPORT request. And another > [2] which allows for a single report to be setup by userspace via IOCTL, > which will be fetched and returned by the kernel for subsequent GET_REPORT > requests by the USB Host, also with no further userspace interaction > possible. > > This patch, while loosely based on both the patch sets, differs by allowing > the option for userspace to respond to each GET_REPORT request by setting > up a poll to notify userspace that a new GET_REPORT request has arrived. To > support this, two extra IOCTLs are supplied. The first of which is used to > retrieve the report ID of the GET_REPORT request (in the case of having > non-zero report IDs in the HID descriptor). The second IOCTL allows for > storing report responses in a list for responding to requests. > > The report responses are stored in a list (it will be either added if it > does not exist or updated if it exists already). A flag (userspace_req) can > be set to whether subsequent requests notify userspace or not. > > Basic operation when a GET_REPORT request arrives from USB Host: > > - If the report ID exists in the list and it is set for immediate return > (i.e. userspace_req == false) then response is sent immediately, > userspace is not notified > > - The report ID does not exist, or exists but is set to notify userspace > (i.e. userspace_req == true) then notify userspace via poll: > > - If userspace responds, and either adds or update the response in > the list and respond to the host with the contents > > - If userspace does not respond within the fixed timeout (2500ms) > but the report has been set prevously, then send 'old' report > contents > > - If userspace does not respond within the fixed timeout (2500ms) > and the report does not exist in the list then send an empty > report > > Note that userspace could 'prime' the report list at any other time. > > While this patch allows for flexibility in how the system responds to > requests, and therefore the HID 'protocols' that could be supported, a > drawback is the time it takes to service the requests and therefore the > maximum throughput that would be achievable. The USB HID Specification > v1.11 itself states that GET_REPORT is not intended for periodic data > polling, so this limitation is not severe. > > Testing on an iMX8M Nano Ultra Lite with a heavy multi-core CPU loading > showed that userspace can typically respond to the GET_REPORT request > within 1200ms - which is well within the 5000ms most operating systems seem > to allow, and within the 2500ms set by this patch. > > [1] https://lore.kernel.org/all/20220805070507.123151-2-sunil@amarulasolutions.com/ > [2] https://lore.kernel.org/all/20220726005824.2817646-1-vi@endrift.com/ > > Signed-off-by: David Sands > Signed-off-by: Chris Wulff > --- > v3: rebased to usb-next, checkpatch cleanup (formatting, lore.kernel.org links) > v2: https://lore.kernel.org/all/CO1PR17MB541952864266039BAA7BBBD3E10F2@CO1PR17MB5419.namprd17.prod.outlook.com/ > v1: https://lore.kernel.org/all/20230215231529.2513236-1-david.sands@biamp.com/ > --- > drivers/usb/gadget/function/f_hid.c | 272 +++++++++++++++++++++++++++- > include/uapi/linux/usb/g_hid.h | 40 ++++ > include/uapi/linux/usb/gadgetfs.h | 2 +- > 3 files changed, 306 insertions(+), 8 deletions(-) > create mode 100644 include/uapi/linux/usb/g_hid.h Breaks the build: drivers/usb/gadget/function/f_hid.c:567:6: error: no previous prototype for ‘get_report_workqueue_handler’ [-Werror=missing-prototypes] 567 | void get_report_workqueue_handler(struct work_struct *work) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ cc1: all warnings being treated as errors