hello every one

i have a doubt on how the data is written and read to and from the character device . i need the complete sequence in few words of which structures are involved and which function is involved untill data is written to the actual hardware


let us assume there is a character device and this is not memory mapped in the kernel space
so my flow would be like this

ioctl(CMD=WRITE) --- system call --- ioctl(CMD=WRITE)
userspace ------------------------->kernelspace------------->

i have show a diagram above which says userspace ioctl call with cmd=WRITE executes kernel space ioctl(CMD=WRITE) present in file_operations structure. after this i wanted to know what are the functions executed so that the data is actually written on the hardware device.
can any one reply to me with your answer.

Nakul

Read up:

and
http://tldp.org/LDP/lkmpg/2.6/html/x569.html

that is not what i was looking at anisha basically how the interaction happen with the character device the one you shown is just a layer above it but i wanted to know what happens when you want read write on the device

do you mean you want to see the assembly code for the same then, i.e. how the registers are set etc ?

hello anisha
see i was mainly looking at

every device in the kernel space is represented by a struct device and then it has a struct device_driver and then there is a struct bus_driver now i wanted to know how the file_operations structure communicates with this struct device_driver and then struct bus_driver to write the data on the character device .

Nakul

I don't know whether I have understood you clearly or not but if you want to know the communications between these internal structures of the device drivers then I think you'll have to read definitions of those functions which are responsible for the same.

yeps agreed done
Thanks a lot for the help

Nakul

If you are not joking then I request you to post here exactly what function definitions of what structures did you read.

hello anisha

why will i joke

i mean view it from a hardware perspective that is not mapped using ioremap for that how a file_operations structure communicates with the struct device

first let me make my self clear do you agree every char device at the low level is represented my struct device yes or no.


Nakul

Not every device has a bus driver.