How to enable DRM driver debug logging in Linux ?

If you are facing some issues with graphics or DRM , display etc.. sometime your may want to enable the DRM drivers all debugging messages so you can narrow down the problems. In Linux the drm kernel drivers source code can be found in drivers/gpu/drm. Enabling verbose debug messages is done through the drm.debug parameter, … Read more

Ubuntu doesn’t detect WiFi Access Point

Recently I came across very different problem when I moved to a place where there was few more access points, my laptop had ubuntu 14.04. [ Note: Users has reported that this works on latest Ubuntu versions also ] $ lsb_release -a I could see lot of other access points in my ubuntu network manager, … Read more

Understanding wireless beacon packet ( captured using pcap API’s )

As per Wikipedia, Beacon frame is one of the management frames in IEEE 802.11 based WLANs. It contains all the information about the network. Beacon frames are transmitted periodically, they serve to announce the presence of a wireless LAN and to synchronise the members of the service set. Beacon frames are transmitted by the access point (AP) in an infrastructure basic … Read more

Wi-Fi Initial Communication between device and access point

Following diagram shows the initial handshaking between the device ( like mobile ) and wireless access-point ( AP ) in open access mode and secured ( e.g. WPA ) mode, Authentication frame ( in open access ): 802.11 authentication is a process whereby the access point either accepts or rejects the identity of a radio … Read more

Passing command line Arguments / Parameters to Linux kernel module

In Our previous post, “Writing first Linux kernel Module and understanding Kernel module compilation, loading and unloading” We learned how to write a simple Linux kernel module. Lets see an example of how to pass the loading time parameters to the kernel module. The load time parameter passing is very helpful to enable / disable … Read more

Writing first Linux kernel Module and understanding Kernel module compilation, loading and unloading

We will try to understand the simple kernel driver which initially we will compile for ubuntu host and later for a embedded hardware. Create a Makefile, Now, compile this kernel module for ubuntu x86 based host, $ make make -C /lib/modules/3.19.0-30-generic/build M=/home/devbee/devlab/module_workspace modules make[1]: Entering directory ‘/usr/src/linux-headers-3.19.0-30-generic’ CC [M] /home/devbee/devlab/module_wokspace/hello.o Building modules, stage 2. MODPOST … Read more

Check Bluetooth services of a remote device

With following mechanism, we can check the bluetooth profiles and services of a remote device, 1) Switch on bluetooth and make it discoverable ( in my case its Samsung Mobile ) 2) On ubuntu, check mac id using below command, $ hcitool inqInquiring …38:EC:E4:50:2C:F7    clock offset: 0x1164    class: 0x5a020c 3) Now to check services and … Read more

Using hcitool to get bluetooth device information

Below commands are shown for communication between Linux Laptop and Samsung Mobile to get Mobile bluetooth device information using hcitool. For this, first make sure laptop bluetooth is turned ON and then switch ON the Bluetooth of Mobile and Make it discoverable/visible to all nearby bluetooth devices. Lets try to understand what is hcitool, $ … Read more

How Android Bluetooth Profiles are enabled & Services activated ?

How Android Bluetooth profiles are enabled ? Ans: Check packages/apps/Bluetooth/res/values/config.xml <resources> 16 <bool name=”profile_supported_a2dp”>true</bool> 30</resources> If you want to disable the above profile, change from “true” to “false” Check related lxr The above flags are used during initialisation as below, in file, packages/apps/Bluetooth/src/com/android/bluetooth/btservice/ Resource flag to indicate whether profile is supported or not. private static … Read more

Understanding Bluetooth Basics – Pairing and Handshaking process

What is Bluetooth? Bluetooth is a standardized protocol for sending and receiving data via a 2.4GHz wireless link. It’s a secure protocol, and it’s perfect for short-range, low-power, low-cost, wireless transmissions between electronic devices. How Bluetooth Works ? The Bluetooth protocol operates at 2.4GHz in the same unlicensed ISM frequency band where RF protocols like … Read more