Re: Beginner query regarding usbhid

From: Randy Dunlap <rdunlap@infradead.org>
To: Rohit Sarkar <rohitsarkar5398@gmail.com>
Cc: Hubert CHAUMETTE <hubert.chaumette@kolabnow.com>,
	Oliver Neukum <oneukum@suse.com>,
	linux-usb@vger.kernel.org, linux-newbie@vger.kernel.org
Subject: Re: Beginner query regarding usbhid
Date: Thu, 26 Mar 2020 09:16:26 -0700	[thread overview]
Message-ID: <4637ad23-b086-b76d-5ce0-99da85764b45@infradead.org> (raw)
In-Reply-To: <5e7cd502.1c69fb81.2402c.714b@mx.google.com>

On 3/26/20 9:14 AM, Rohit Sarkar wrote:
> On Thu, Mar 26, 2020 at 09:02:55AM -0700, Randy Dunlap wrote:
>> On 3/26/20 12:34 AM, Rohit Sarkar wrote:
>>
>>>>>>>
>>>>>>> The command I used for building was "make -C /home/rohit/LINUX/kernels/staging  M=$(pwd)"
>>>>>>> and for installing the modules: "sudo make -C /home/rohit/LINUX/kernels/staging  M=$(pwd) modules_install"
>>>>>>> both were executed from the usbhid directory.
>>>>>>
>>>>>> why those commands?  seems unusual.
>>>>> My Linux kernel source is in the directory mentioned in the commands. So
>>>>> it is same as running "make M=drivers/hid/usbhid/" from the linux kernel
>>>>> source root.
>>>>
>>>> So /home/rohit/kernels/staging is the top-level kernel source directory?
>>>>
>>>> "M=dir" is for external modules to be built.  AFAICT you are not building any
>>>> external modules.
>>>>
>>>> Just run
>>>> $ cd <top of kernel source tree>
>>>> $ make all
>>>> $ sudo make install
>>> Further, on my system it takes a significant amount of time to run "make
>>> all" for some reason. (30 minutes) even though I have previously
>>> built the kernel and not pulled any update.
>>> AFAIK, make is only supposed to build the files that have
>>> changed. Idk why it is also compiling other files. Most of the time is
>>> taken by make running modpost.
>>>
>>> That is the reason I tried to build and install only the hid folder
>>
>> OK, I get that.
>>
>> For a driver that is built as a loadable module, you should be able to
>> edit the driver, build it, unload previous version (rmmod),
>> load new version (modprobe or insmod), and test it, without having to
>> reboot the kernel. [until an oops or BUG or WARN happens]
>>
>> If you don't "install" the new module file, I think that modprobe will
>> look in /lib/modules/kernel_version/* for the module file and find the
>> old one.  In this case I usually use "insmod path_to_new_driver_file"
>> to load & test it.
> Hmm, the weird part is that I did run "sudo make modules_install".
> Shouldnt that get the latest modules into /lib/modules/{kernel
> version}/*. Although it didnt work before rebooting.

Yes.

> I guess insmod path_to_new_driver_file is the best option here.

-- 
~Randy