devregs - tool to display and modify a device's registers at runtime

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DEVREGS - Is a tool to display and modify a device's registers at runtime.

Under Linux, you can access registers, or any area of physical memory through the /dev/mem pseudo-device and the wonders of the mmap system call. To use it, you open the /dev/mem device, mmap the page in which a register is located, then use the pointer returned to read and/or write the data. Boundary Devices, developed a tool known as " devregs  " that allows you to put a little structure around this facility. It allows you to give names to particular physical memory areas and to describe the bits within a register in the text file /etc/devregs.dat.

How to read from register :

To read one or more registers, use devregs with a single parameter that’s either an address or a register name.

Ex : $  devregs 0x73f88000

:0x73f88000    =0x803dffaf

If a register address matches a register in /etc/devregs.dat, you’ll see the register name:

Ex : $ devregs 0x73f88000

GPIO2_DR:0x73f88000    =0x803dffaf

If used with a register name, any bitfields defined will be shown:

Ex: devregs UART1_UFCR

UART1_UFCR: 0x73fc0090   =0x0801

UART1_UFCR:0x73fc0090    =0x0801

      TXTL                      10-15     =0x2

      RFDIV                    7 - 9      =0x0

      DCEDTE                 6 - 6     = 0x0

      RXTL                       0 - 5     = 0x1

How to write to register :

Ex : $ devregs GPIO2_GDIR

GPIO2_GDIR:0x73f88004    =0x0002c0a4

Ex: $ devregs GPIO2_GDIR 0x2c0a0

GPIO2_GDIR:0x73f88004    =0x0002c0a4

GPIO2_GDIR:0x73f88004 == 0x0002c0a4...0x0002c0a0

Ex: $ devregs GPIO2_GDIR

GPIO2_GDIR:0x73f88004    =0x0002c0a0

For more detailed information please go through the following below links :

http://boundarydevices.com/i-mx5x-device-register-access/

http://boundarydevices.com/configuring-i-mx6-machines-different-screens-nitrogen6x-sabre-lite/