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SubjectRe: [PATCH] Drop second arg of unregister_chrdev()
On Mon, Aug 14, 2006 at 08:48:17PM -0700, Andrew Morton wrote:
> On Tue, 15 Aug 2006 07:35:22 +0400
> Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> > * "name" is trivially unused.
>
> OK.
>
> > * Requirement to pass to unregister function anything but cookie you've
> > got from register counterpart is wrong. It creates opportunity to
> > diverge, it create opportunity for bugs if enforced:
> >
> > /*
> > * XXX(hch): bp->b_count_desired might be incorrect (see
> > * xfs_buf_associate_memory for details),
> >
> > Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> >
> > * but fortunately
> > * the Linux version of kmem_free ignores the len argument..
> > */
> > kmem_free(bp->b_addr, bp->b_count_desired);
>
> I don't understand that.

p = malloc(size);
free(p);
is good. You don't have to remember "size" which sometimes nontrivially
calculated until free time.

mmio = ioremap(start, size);
iounmap(mmio);
is good too for same reasons. Agree so far?

Ergo,
major = register_chrdev(0, "foo", &foo_fops);
unregister_chrdev(major);
is good too even if people don't forget to pass the same "foo" in two
places. Luckily, unregister_chrdev() ignores name arg, so passing wrong
won't do any harm.

> > 64 files changed, 97 insertions(+), 97 deletions(-)
>
> I do understand that. This'll cause some grief.

In kernel, hardly...

$ grep unregister_chrdev -w -n 2.6.18-rc4-mm1
33126: unregister_chrdev(CPUID_MAJOR, "cpu/cpuid");
35853: unregister_chrdev(MSR_MAJOR, "cpu/msr");
35861: unregister_chrdev(MSR_MAJOR, "cpu/msr");
134610: unregister_chrdev(LP_MAJOR, "lp");
291207:- unregister_chrdev(hptiop_cdev_major, "hptiop");
352167:+ unregister_chrdev(major_number, "SerialQT_USB");

Two rejects, 4 fuzzy places.

> I'd suggest that we add a
> new unregister_char_dev() or something, and do

But there is register_CHRDEV_region, unregister_CHRDEV_region,
alloc_CHRDEV_region, register_CHRDEV. Should I change the spelling of
register_chrdev() for a good measure, too?

> static inline unregister_chrdev(unsigned int major, const char *name)
> {
> return unregister_char_dev(major);
> }

> then migrate callers over to unregister_char_dev() in an organised fashion,
> via maintainers where poss.
>
> Then mark unregister_chrdev() deprecated for a while.
>
> Then nuke it.

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