linux-kernel - Re: [PATCH 01/13] proc tty: introduce ->proc

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Date:	Sat, 2 Aug 2008 07:45:11 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/13] proc tty: introduce ->proc_fops

On Tue, Jul 29, 2008 at 10:53:50AM +0100, Alan Cox wrote:
> On Tue, 29 Jul 2008 05:29:08 +0400
> Alexey Dobriyan <adobriyan@...il.com> wrote:
> 
> > Add struct tty_operations:proc_fops .
> > 
> > The intent is gradual switch of TTY drivers from ->read_proc usage.
> > proc entries are created with proc_create_data() which even fixes
> > early-read races.
> > 
> > Eventually ->read_proc code will be removed from TTY code, thus helping
> > remove ->read_proc from whole proc code.
> 
> I'm going to NAK this but not because I think the concept is wrong. I
> think the way its been done is perhaps wrong.
> 
> You've added ifdefs to a lot of drivers and more basically duplicate
> code.

It's boileplate code which is hard to screwup, unlike boilerplate at the
end of every ->read_proc hook.

> Is there a reason you can't keep the ->read_proc method in the tty
> code but as a function called by a single instance of proc_fops and
> seq_file methods for the whole tty driver layer.
> 
> Ie have a single tty seq_file method that calls driver->ops->read_proc as
> the seqfile iterator ?

I think it should be struct tty_operations::proc_fops .

In fact, posted conversions are bit incorrect.

Let's look at cyclades. It prints banner, then information about each
card. The very right way to print it via seq_files is implement
struct seq_operations::start, next, stop, show.

If TTY driver prints something simple, just one show hook is enough.
If TTY driver wants something more complex, right way start to be
seq_operations and one hook is not enough anymore.

But I don't really care about this exact issue, as long as ->read_proc
TTY hook is gone as ->read_proc proc hook.

> >  int count, int *eof, void *data);
> > +#ifdef CONFIG_PROC_FS
> > +	const struct file_operations *proc_fops;
> > +#endif
> 
> I'd prefer you didn't put variables in the middle of the methods. Also
> the ifdef isn't needed. It's not worth one pointer to create a load of
> ifdefs

OK.

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