how to write a Linux - USB Device driver, that should mount as cd-rom on mac

We can't seriously be expected to teach you that. That's a BIG project is expect (although you've not described anything about it) we could never ever teach you that.

Hello and welcome to LQ!

You can't write Linux device drivers for MacOS X, since MacOS X does not use a Linux kernel.
If that is not what you want please be more specific in your question. What is it exactly that you want to achieve?

Sidenote: Thread titles like "Help me!! Please !!" are not a good thing and may drive people away from your thread. Please give your thread more appropriate titles in the future, this way you may get better results for your questions.
Since it is not really clear to what you really want to achieve I temporarily rename this thread to "Need help writing Linux/MacOS X USB driver" and move it to the main hardware section, since this is not a Embedded question.
If this is not what you want please send me an email or ask for a change here.

I am working in driver development in linux USB modules.
I have written driver for usb and it is working as cd rom in windows machine

1)I made first partation as fat32
"modprobe g_hidmass file=/dev/mmcblk0p1 cdrom=1 stall=0 removable=1"
this works fine in windows

2)I made first partition as hfs partation
"modprobe g_hidmass file=/dev/mmcblk0p1 cdrom=1 stall=0 removable=1"

but same thing i applied with hfs partation in MAC it is getting error
like this "The disk you inserted was not readable by this computer"
in diskutil it is shown as CD-rom but not reading the file system.
frame like this

Please help me how can I overcome this error...

If I understand you correctly you want to write a driver for MacOS X for a USB drive (harddisk, pendrive, CD/DVD-drive?), so that the device acts as a CDROM drive. Since this is not a Linux question I would recommend to ask this question in an Apple forum, but I will move this to the programming section and change the title accordingly.
May be some of our members are familiar with MacOS X kernel coding.

I want to write driver in Embedded Linux in Freescale IMX Series...
Though it is for MacOS X but need to write driver in Embedded Linux only..Hope you understand my question