From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jose Diez Subject: Re: Help writing a custom HID driver Date: Thu, 06 Nov 2014 20:56:00 +0000 Message-ID: <545BE060.7020600@mediacru.sh> References: <545BBF05.9030203@mediacru.sh> <545BCBE9.6040309@mediacru.sh> <545BD794.7090002@mediacru.sh> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mediacru.sh ([5.254.104.62]:48301 "EHLO mediacru.sh" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750706AbaKFU4F (ORCPT ); Thu, 6 Nov 2014 15:56:05 -0500 In-Reply-To: Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Benjamin Tissoires Cc: linux-input Ah, I was hoping there would be a way to avoid having to patch the kernel itself. Thanks again, Jose On 06/11/14 20:22, Benjamin Tissoires wrote: > On Thu, Nov 6, 2014 at 3:18 PM, Jose Diez wrote: >> Okay, so I've solved the watchdog issue, and now I want the driver to be >> loaded automatically. I've copied the module to /lib/modules// and >> run depmod -a, and I can see it in modules.alias, but it looks like >> hid_generic grabs it first upon boot - my module is loaded correctly, but it >> doesn't grab the HID device. >> >> If I `modprobe -r hid_generic` and then load my module, everything works >> correctly. > Yep. You need to add your device VendorID/ProductID in > hid_have_special_driver[] in hid-core.c. > This will tell hid-generic not to grab your device, and your custom > module will take over. > > Cheers, > Benjamin > >> On 06/11/14 19:28, Jose Diez wrote: >>> Thanks Benjamin. That fixed the issue. Have a great day. >>> >>> On 06/11/14 18:57, Benjamin Tissoires wrote: >>>> Hi Jose, >>>> >>>> On Thu, Nov 6, 2014 at 1:33 PM, Jose Diez wrote: >>>>> Hello linux-input, >>>>> >>>>> I'm trying to write a custom HID driver. It works fine, and I can send >>>>> reports just fine, but one of the requirements of this device is that I >>>>> have >>>>> to reply to reports with code 62 with another report with code 62, which >>>>> resets a watchdog in the device. >>>>> >>>>> This is my code so far:http://codepad.org/m4QiWhDt >>>>> >>>>> The problem is in line 40. It seems like I'm not allowed to call >>>>> hid_hw_output_report from the raw_event callback handler. I've tried >>>>> surrounding the call with spin_locks, but I still get the "scheduling >>>>> while >>>>> atomic" error. >>>> Yeah, when you are in the .event callback, you are basically called by >>>> an IRQ, so you can not schedule a potentially blocking operation. >>>> >>>>> I'm not sure how to approach this - can someone help? It would be much >>>>> appreciated. Thanks. >>>> I would use a worker to do what you are trying to do. You can have a >>>> look at the reset_worker we have in drivers/hid/hid-rmi.c. >>>> When the event is not one we expected, we schedule a worker thread >>>> which then sends an output report to the device. This way, the >>>> blocking operation is sent from a different thread than the IRQ one. >>>> It is kind of what you are willing to do. >>>> There are many other examples of workers in the hid subtree, or you >>>> can refer to the doc to find out more. >>>> >>>> Cheers, >>>> Benjamin >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-input" in >>>> the body of a message tomajordomo@vger.kernel.org >>>> More majordomo info athttp://vger.kernel.org/majordomo-info.html >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-input" in >>> the body of a message tomajordomo@vger.kernel.org >>> More majordomo info athttp://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-input" in > the body of a message tomajordomo@vger.kernel.org > More majordomo info athttp://vger.kernel.org/majordomo-info.html