Hi,
The 'binder' kernel driver registers itself with the kernel under a device
name, e.g. /dev/binder. Using "binder_fops" is passes all of the module's
functions to the kernel as callbacks for different events (open, mmap,
flush, release, etc against that device name).
So the Binder IPC client must open("/dev/binder", ...) as a file descriptor
and then read and write to the descriptor to pass data to the binder kernel
driver. An 'mmap' in this case, maps memory between processes, but it is
associated with this file descriptor to tell the kernel that the binder
module is responsible for managing the process of memory sharing between the
kernel module and the client process.
Cheers,
Nigel
On Wed, Sep 28, 2011 at 11:48 AM, AndroidHolder <[email protected]> wrote:
> First,to be honest,my doubt comes from the binder driver part in /
> kernel/drivers/android/binder.c
> // 1. register binder as a misc device
> static int __init binder_init(void){
> int ret;
> ...
> ret = misc_register(&binder_miscdev);
> ...
> }
> // 2.declare fops as &binder_fops
> static struct miscdevice binder_miscdev = {
> .minor = MISC_DYNAMIC_MINOR,
> .name = "binder",
> .fops = &binder_fops
> };
> // 3.binder_fops is defined as follows
> static struct file_operations binder_fops = {
> .owner = THIS_MODULE,
> .poll = binder_poll,
> .unlocked_ioctl = binder_ioctl,
> .mmap = binder_mmap,
> .open = binder_open,
> .flush = binder_flush,
> .release = binder_release,
> };
> Then take a look at /framework/base/cmds/servicemanager/binder.c,there
> are one place where runs ioctl and another place where runs mmap.
> int binder_become_context_manager(struct binder_state *bs)
> {
> return ioctl(bs->fd, BINDER_SET_CONTEXT_MGR, 0);
> }
> struct binder_state *binder_open(unsigned mapsize)
> {
> struct binder_state *bs;
>
> ...
> bs->mapped = mmap(NULL, mapsize, PROT_READ, MAP_PRIVATE, bs->fd,
> 0);
> ...
> }
> Since above,I am not sure the relationship between ioctl() and
> binder_ioctl() defined in driver ,along with the relationship between
> mmap() and binder_mmap() defined in driver,could someone help me to
> make it clear,thanks.
>
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