Is there a better solution to get the minor number?
Can I avoid checking kernel version?
static long unlocked_ioctl(struct file *f, unsigned int o, unsigned long d)
{
#if KERNEL_VERSION(3, 18, 0) > LINUX_VERSION_CODE
struct inode* inode = f->f_dentry->d_inode;
#else
struct inode* inode = f->f_path.dentry->d_inode;
#endif
int minor = iminor(inode);
}
As an addendum to Marco Bonelli's answer, file_inode()
was added in the 3.9 kernel, so if earlier kernel versions need to be supported, some kernel compatibility code needs to be added. I use something like the following:
/*
* The file_dentry() inline function was added in kernel version 4.6.0.
* Emulate it for earlier kernels.
*/
#if LINUX_VERSION_CODE < KERNEL_VERSION(4,6,0)
static inline struct dentry *kcompat_file_dentry(const struct file *f)
{
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
return f->f_dentry;
#else
return f->f_path.dentry;
#endif
}
#undef file_dentry
#define file_dentry(f) kcompat_file_dentry(f)
#endif
/*
* The file_inode() inline function was added in kernel 3.9.0.
* Emulate it for earlier kernels.
*/
#if LINUX_VERSION_CODE < KERNEL_VERSION(3,9,0)
static inline struct inode *kcompat_file_inode(struct file *f)
{
return file_dentry(f)->d_inode;
}
#undef file_inode
#define file_inode(f) kcompat_file_inode(f)
#endif
Yes, there's a better way: don't bother looking at the dentry
when what you want is right there as a field of struct file
.
struct file {
union {
struct llist_node fu_llist;
struct rcu_head fu_rcuhead;
} f_u;
struct path f_path;
struct inode *f_inode; // <-- here's your inode
// ...
}
You can either access f->f_inode
directly or use the file_inode()
function, this way you can also avoid kernel version checks.
static long unlocked_ioctl(struct file *f, unsigned int o, unsigned long d)
{
int minor = iminor(file_inode(f));
// ...
}
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