Messages in this thread |  | | From | Arnd Bergmann <> | Subject | Re: ioctl cleanups: enable sg_io and serial stuff to be shared | Date | Wed, 7 May 2003 21:13:07 +0200 |
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On Wednesday 07 May 2003 18:04, David S. Miller wrote: > You can define it as follows: > > 1) If entry exists in COMPAT or TRANSLATE table, invoke > fops->ioctl(), else > > 2) If ->compat_ioctl() exists, invoke that, else > > 3) Fail.
Another solution could be to use the tables only if ->compat_ioctl() is undefined or returned -ENOTTY. That would save the hash table lookup in many cases and makes it possible for a driver to override a generic handler with its more specialized version (e.g. CIODEVPRIVATE).
> The COMPAT tables are sort of valuable, in that it eliminates > the need to duplicate code when all of a drivers ioctls need > no translation.
Right. Of course you can just as well do
.ioctl = &foo_ioctl, .compat_ioctl = &foo_ioctl,
in that case.
Btw: is there any bit in the ioctl number definition that can be (ab)used for compat_ioctl? Maybe we don't even need another callback if the compatibility mode can be encoded in the number itself (simplified):
long compat_sys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg) { long err = sys_ioctl(fd, cmd | _IOC_COMPAT, arg); if (err == -ENOTTY) /* use ioctl_trans table */ err = compat_do_ioctl(fd, cmd, arg); return err; } ... long foo_ioctl(struct inode * inode, struct file * filp, unsigned int cmd, unsigned long arg) { switch(cmd) { case SOMEIOCTL: return do_something(inode, arg); case SOMEIOCTL | _IOC_COMPAT: return compat_do_something(inode, arg); case ANOTHERIOCTL: case ANOTHERIOCTL | _IOC_COMPAT: return do_something_else(inode, arg); } return -ENOTTY; }
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