How can I print device stacks of specific devices? I.e. for specific keyboard I'll get: [usb device]->[kb device]->[filter1]->... or something like this?
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Linux newbie question.
Just wondering how Linux determines which device class a device is? Specifically, when I plug a barcode scanner in how does it know it is an ttyACM device? I have a scanner that works with my Linux OS but the new model isn't recognized so I'm wondering if I can alter a file somewhere in the system that tells it to recognize the scanner as ttyACM0 and use the existing drivers.
USB devices (I assume your scanner is USB) are identified by vendorId and productId (two 16bit integers), each driver fill an array with the list of supported vendor/prods id (creating a relation vendor:prod->driver), I guess at compile time all the id in the array are merged together in a list which then is used for a lookup search when a device is plugged in.
Usually you can see vendor and product id of the attached device with dmesg command right after the device is plugged in (or with lsusb).
For ttyACM see acm_ids[] in drivers/usb/class/cdc-acm.c
Careful playing around with device drivers, even being ttyACM a terminal interface only if the interface tty->hardware is implemented poorly some command may break the hardware.
Perhaps this question should be in Unix & Linux stackexchange
I'm building a USB HID device using Arduino Leonardo mini clone, based on ATmega32u4. That particular IC has got a USB controller built in, and turning it in to a HID device is simple. You just need to include Keyboard.h and then use Keyboard.print...
Where can I set/define the name of the device that is shown, when that Arduino is connected to a PC, because at the moment it is named Arduino Leonardo.
The default automated name for tty is usbmodemHIDP1.
In system preferences, I can see:
ID product: 0x8036
ID vendor: 0x2341
Wersion: 1.00
Serial number: HIDPC
Speed: do 12 Mb/sek.
Vendor: Arduino LLC
ID location: 0x14200000 / 16
So where in Arduino is file Keyboard.h? Can I change that name, or ID's?
Is it possible?
Because in my opinion it should be, but I just can't find the right place, and I do not have experience with Arduino AVR as I was working with Microchips Mplab X before for different ICs ;).
The "iProduct" string sent by the board on enumeration tells the operating system to give it the human-readable name. The value of that string is set near the top of USBCore.cpp in hardware/arduino/cores/arduino/. It's a Unicode string, so we need looking for 'L', 'e', 'o', 'n' [...], not "Leonardo". The string used depends on the PID number of the device (also sent during enumeration) which is given in boards.txt.
For distributing own custom hardware based on the Leonardo, there is a need to provide your own VID.
Also there can be used alternative firmware.
The Arduino '32U4 bootloader, Caterina, can be found under hardware/arduino/bootloaders/caterina. It requires LUFA in order to build.
I am trying to understand how to address devices behind I2C Mux like PCA9548 in linux.
If the topology is something like
CPU->I2C_A Controller->PCA9548->Channel 0->RTC
CPU->I2C_A Controller->PCA9548->Channel 1->Temp Sensor
CPU->I2C_B Controller->PCA9548->Channel 0->Voltage Sensor
CPU->I2C_B Controller->PCA9548->Channel 1->Speed Sensor
I want to know the representation of these devices in user space? What are the associated sysfs entries?
I also want to know if pc9548 is the only driver required in kernel and i2c-dev and i2c-core are already available? Or driver for RTC/sensors is also required?
I have tried to read this, but could not follow it much.
My requirement is to read/write to those devices from user space. Do I have to instantiate devices and assign addresses to it in startup script?
Thanks,
Hemant
You could use i2c-tools for manipulation at user space, if the driver has some problem.
Also you'll need enable the kernel module "i2c-dev" for the char device.
Like /dev/i2c-0
link here.
The necessary driver are i2c-mux, pca954x, I believe you already have i2c-core.
Also you should describe all the I2C devices in device tree or other files.
If the driver is prepared, you may see 8 i2c adapters under /dev, and their salve device is under /sys/bus/i2c.
I'm developing a driver for an FPGA-board connected to my machine via an PCIe expansion slot, and everything works great if the board is powered on prior to the PC. However, if I book up my computer first and then the FPGA board, I get the rather unusual behavior of the device being recognized and loading my module (I see the "init" function called in my syslog), however the "probe" function is never called.
I think this is due to an invalid BAR0. Output from dmesg when I power on the board:
[ 71.287587] pci 0000:3b:00.0: [0ae5:0001] type 00 class 0x000000
[ 71.287613] pci 0000:3b:00.0: reg 0x10: [mem 0x00000000-0x0000ffff]
[ 71.287821] pci 0000:3b:00.0: System wakeup disabled by ACPI
[ 71.328537] my_driver:
[ 71.328537] ****************************************************************
[ 71.328542] my_driver: init debug=2
That first reg should be something like 0xb4000000-0xb400ffff but instead it's coming up as 0. (Like I said, it works perfectly if it's powered on before the computer).
Is there an additional step required to get it to allocate this block? Or somehow to indicate to the kernel that it needs to do this?
The solution wound up being a manual call to pci_assign_resource ( http://lxr.free-electrons.com/source/drivers/pci/setup-res.c#L283 ).
Calling this right before pci_enable_device caused the OS, rather than the BIOS, to allocate the required BAR's and now it all works!
I do still have to manually trigger a PCI bus rescan ( echo 1 > /sys/bus/pci/rescan ).
Your PCI device must be powered up prior to the BIOS PCI enumeration phase.
On enumeration phase, the BIOS tries to read the ID of the PCI devices that might be connected.
If it reads invalid ID (0xfffff) it skips that PCI device.
I don't have a reference, but AFAIK, you have about a second before you must populate the configuration space of the PCI.
Are you sure you register the PCI driver and don't return non-zero from mod_init? Please try to manually bind the device to your driver:
echo -n "0000:3b:00.0" > /sys/bus/pci/drivers/my_driver/bind
Unallocated BAR should not be an issue when loading the driver.
As for the BAR being 0 and HotPlug: find out what is your platform and if and how HotPlug is supported. You need to have the right HotPlug driver in the kernel for this sort of thing to work. BARs are allocated by the kernel (or initially firmware/BIOS) so you can't set them to anything meaningful from the FPGA side - there you can only set the size. Kernel has to do the rescanning and reassignment after device appears. I vaguely recall that there should be some reservation going on during boot, otherwise kernel will not have to space to give to your devices' BAR and it will not reassign the windows on bridges below your device as they can be actively used by other devs. Other option is to just do the BAR programming yourself from the driver. It ain't that hard but you would probably don't want to ship this kind of hacks to customers. Also, even though your device does seem to come up fine, make sure you don't have HP disabled in FW/BIOS.
I have a Linux USB HID device (a Hama MCE), and I can read its events manually by reading cat /dev/input/event7 and cat /dev/input/event8. Whenever I press a key on the device, a few bytes become available for reading with one of the cat commands above. I have a default installation of Ubuntu Jaunty 64-bit desktop on the machine.
I think I can write a parser to interpret the bytes emitted by the device, or I'll use libhid if it's more convenient.
My questions are:
How do I prevent the text-mode virtual consoles from receiving some of the key presses on the device as normal keypresses? As of now, some device keys result an Enter, a BackSpace, a PageUp or numeric keypad numbers.
Similarly, how do I prevent the X server from receiving keyboard and mouse events from this device? I have several USB keyboards and mice connected to the computer. I want the X server receive events from all of them, except for this device.
How do I set up that whenever the device gets connected to the computer, the command /usr/local/bin/keydumper /dev/input/event7 /dev/input/event8 (or one command for each /dev/ path) would get run, with the proper /dev/ paths substituted in the command line?
Answering my own question based on answers from the Linux USB HID driver developers:
Question 1. and 2.: Do
ioctl(open("/dev/input/event7", O_RDONLY), EVIOCGRAB, 1);
As long as this filehandle is open, the events generated would go only
to this filehandle (not to other open()s of the same device or to the
system keyboard or mouse event pool). At most one process can hold a
successful EVIOCGRAB at a HID device at a time. Lirc can be configured
to do an EVIOCGRAB.
Question 3.: Configure udev to start the program once the device is connected.
I do not have enough points to comment sadly.
If you are looking for the definition of EVIOCGRAB try
#include <linux/input.h>
I think solution for all questions can be writing own filter device driver, or custom driver for your device. I know such a thing (filter device driver) is available on windows so something similar can be on Linux. In that filter device driver you could block all unwanted events from the target device that you wish to block, I don't really get 3 question so I don't know how to answer for that.