CODEWITHSUNDEEP
linuxlinux-device-driver
pradiptart
pradiptart

Reputation: 970

Which h/w knoledge needed to have to become a Device driver programmer?

I am very interested in device driver programming .I have started reading the LDD3 ,there author said

"to become a device driver programmer you have to understand your specific device well"

can any one tell me what is the meaning of the "understand your specific device" .what are the thing I should know before writing a device driver.

Thanks

Upvotes: 0

Views: 296

Answers (2)

shawn xy bai
shawn xy bai

Reputation: 158

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Hi, I'm very pleased to share what I have learnt with you guys.

Yes, it is the basic need to know your device if you wanna be a device driver programmer. I also want to be a linux device driver programmer, or even more, though I have some device driver experience under other software platforms.

The reason why you wanna contact with it is that you wanna make it do something for you.

Normally, what it can do is the first thing you must know. It's very obvious that you will never send Ethernet frames through UART or SPI, right?

There exist various kinds of devices in the world, such as, storage device, FLASH, SD card, harddisk; communicating devices, network card, wifi; interconnected bus, PCI-express; how many there are.

After that, the next thing you will concern is how you can do to reach your goal. To access the device, reading, or writing, there is usually a controller embedded in the processor. Here, when I say "processor", it means it is a core integrated with various kinds of controllers, no matter pc desktop or embeded system areas.

The Controller is the interface you will face, to work on the device behind the controller. Through the controller, you can ask the device to do what you want. In the controller, there are registers, which are the deepest points the software can touch. Beyond that lies the hardware, as you are a device driver programmer, it is very common for you to communicate with hardware engineers to make things done.

If going into details about the register, there are control registers used to tell device what you want it to do, status registers, used to reflect the status of operations underway in devices, if interrupt is supported by that device, there are also some registers for you to deal with interrupts.

Well, I almost forget there are also data registers, whicha are used to store the data to be sent or written, or to be read by user. According to the specific implementation, registers used to store data from upper users to be sent or written and registes used to hold data from outside that will be read by users may be the same, or may be not.

In a normal way, if you wanna let someone do something for you, you should provide something to him first. Whoever wants to do anything, there must be some inputs to him, right?

in a summary,

action(read,write,or others) + data(you give, or you ask for) + status(what progress it is)

  1. what it can do

  2. how it does that, how to assemble the command cell, time sequence?

  3. what you must provide it to reach your goal
    genarally, two kinds of things you should provide:

    if you ask for, where to store what you ask for;
    if you give, where are what you give

  4. how it reflects the progress of operations， polling or interrupts

Well, that is all I want to share with you.

Thanks.

Upvotes: 2

Vinayak Kolagi
Vinayak Kolagi

Reputation: 1881

That's a basic list with software and hardware combined.

The Operating System driver API
The processor architecture as it relates to hardware interfacing
The 'bus' structure that interfaces the device hardware to the processor
Interrupt Handling
Dma Control
Processor Caching
Processor MMU control
OS Semaphores and scheduling
Data/Byte Alignment
Assembly language when needed
Control of Instruction Execution Order and Optimization
Consideration of performance issues

What's IO and memory mapped hardware ?

http://www.cs.nmsu.edu/~pfeiffer/classes/473/notes/io.html

This link talks about generic hardware access in Linux device drivers.

http://www.linuxforu.com/2011/06/generic-hardware-access-in-linux/

This is specifically about USB hardware

http://www.beyondlogic.org/usbnutshell/usb2.shtml

Check lwn.net it never disappoints a device driver developer.

https://lwn.net/Archives/

Last, but not least, They have everythig, CPU, Memory, Camera, PCI..

http://www.hardwaresecrets.com/page/memory

Upvotes: 2

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