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: Wed, 25 Mar 2020 23:07:55 -0700	[thread overview]
Message-ID: <fdc818d7-842c-cfef-3654-0478e74bfa73@infradead.org> (raw)
In-Reply-To: <5e7c3e48.1c69fb81.7da14.34ab@mx.google.com>

On 3/25/20 10:31 PM, Rohit Sarkar wrote:
> On Wed, Mar 25, 2020 at 02:40:27PM -0700, Randy Dunlap wrote:
>> On 3/25/20 10:13 AM, Rohit Sarkar wrote:
>>> On Wed, Mar 25, 2020 at 04:41:38PM +0100, Hubert CHAUMETTE wrote:
>>>> Le 25/03/2020 15:47, Rohit Sarkar a écrit :
>>>>> I was trying to mess around with the driver that drives my mouse. I
>>>>> found out that it is usbhid. I then added a printk statement to the init
>>>>> and exit function of usbhid.
>>>>> I then compiled and installed the usbhid drivers. Post that I ran
>>>>> `sudo modprobe -r usbhid` and `sudo modprobe usbhid` but couldnt observe
>>>>> any logs in dmesg.
>>>>>
>>>>> I am certain I am missing something fundamental. Could someone help me
>>>>> with this.
>>>>
>>>> Hi,
>>>>
>>>> Did you check whether your module was effectively loaded with lsmod?
>>>> What log level did you use in your printk statement? Depending on your
>>>> system default loglevel your logs might not be printed. A quick fix
>>>> would be to use one of the lowest levels (pr_emerg, but pr_err might
>>>> suffice).
>>>> Regards,
>>>
>>> Hey,
>>> I did check that module was loaded. And one of the signs was that my
>>> mouse started working after insmod :).
> Hi,
>> Hi,
>> I'm not convinced that your modified usbhid module was loaded.
> Hmm, here's my dmesg logs if that helps:
> "
> [  382.132319] usbcore: deregistering interface driver usbhid
> [  391.077410] input: MOSART Semi. 2.4G Wireless Mouse as /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2:1.0/0003:3938:1031.0002/input/input26
> [  391.136724] input: MOSART Semi. 2.4G Wireless Mouse as /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2:1.0/0003:3938:1031.0002/input/input27
> [  391.137285] hid-generic 0003:3938:1031.0002: input,hiddev0,hidraw0: USB HID v1.10 Mouse [MOSART Semi. 2.4G Wireless Mouse] on usb-0000:00:14.0-2/input0
> [  391.137480] usbcore: registered new interface driver usbhid
> [  391.137483] usbhid: USB HID core driver
> "

I can't tell that helps any.

>> Could an older (original) usbhid module be reloaded so that the mouse
>> started working again?  That would also explain the lack of (new) messages.
> I think so too. But how do I verify if this is the case?
> 
>> What kernel version are you using?  Is it a distro kernel?
> I am currently running a bleeding edge kernel that I built. ie 5.6-rc7. 
>> Are you trying to replace the usbhid module in a distro kernel or are
>> you building the entire kernel?
> I am building the entire kernel
>>> I used printk(KERN_ALERT "some message") for logging. I also tried with
>>> KERN_ERR but no luck. 
>>>
>>> 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

-- 
~Randy