Re: Beginner query regarding usbhid

[Rohit Sarkar <rohitsarkar5398@gmail.com>]

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
"
> 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.
> -- 
> ~Randy
> 

Thanks,
Rohit