Date:   Mon, 14 Aug 2023 17:47:12 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Jiri Slaby <jirislaby@...nel.org>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/36] tty: type unifications -- part I.

On Mon, 14 Aug 2023, Jiri Slaby wrote:

> On 11. 08. 23, 12:26, Ilpo Järvinen wrote:
> > On Thu, 10 Aug 2023, Jiri Slaby (SUSE) wrote:
> > 
> > > Currently, the tty layer ops and functions use various types for same
> > > things:
> > > * characters and flags: unsigned char, char are used on a random basis,
> > > * counts: int, unsigned int, size_t are used, again more-or-less
> > >    randomly.
> > > 
> > > This makes it rather hard to remember where each type is required and it
> > > also makes the code harder to follow. Also the code has to do min_t() on
> > > many places simply because the variables hold the same kind of data, but
> > > of different type.
> > > 
> > > This is the first part of the series to unify the types:
> > > * make characters and flags 'u8'. This is what the hardware expects and
> > >    what feeds the tty layer with. Since we compile with -funsigned-char,
> > >    char and unsigned char are the same types on all platforms. So there
> > >    is no actual change in type.
> > > * make sizes/counts 'size_t'. This is what comes from the VFS layer and
> > >    some tty functions already operate on this. So instead of using
> > >    "shorter" (in term of bytes on 64bit) unsigned int, stick to size_t
> > >    and promote it to most places.
> > > 
> > > More cleanup and spreading will be done in tty_buffer, n_tty, and
> > > likely other places later.
> > > 
> > > Patches 1-8 are cleanups only. The rest (the real switch) depends on
> > > those.
> > 
> > Yeah, very much needed change and step into the right direction!
> > 
> > It's a bit tedious to review all this and comment a particular subchange
> > but e.g. n_tty_receive_buf_common() still seems to still have int count
> > which I think fall into the same call chain about size/count (probably
> > most related change is #15). Note though that it also has room which I
> > think can actually become negative so it might not be as straightforward
> > search and replace like some other parts are.
> 
> tl;dr
> https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/commit/?h=devel&id=9abb593df5a9b9b72d13438f1862ca67936f6b66
> 
> ----
> 
> Yes, sorry, my bad -- I forgot to elaborate on why this is "part I." and what
> is going to be part II., III., ...
> 
> So yeah, I have more in my queue which is growing a lot. I had to cut it at
> some point as I was losing myself in all the changes already. So I flushed
> this "part I.". It is only a minimalistic change in the core and necessary
> changes in drivers' hooks. Parts II. and on will spread this more, of course.
> Ideally, to every single loop in every driver ;) (in long-term).
> 
> I still have a bunch of changes for tty_buffer and n_tty in my queue. As soon
> as I rebase on the today's -next which is already supposed to contain this
> part I., I will send part II. with these changes. I could have merged those
> II. changes to some earlier I. patches. At first, I actually did try, but the
> patches were growing with more and more dependencies, so I stopped this
> approach. Instead, I separated the changes per the core/ldisc/drivers. The
> parts are self-contained, despite it might look like the changes are
> incomplete (i.e. not everything is changed everywhere). After all, I wanted to
> avoid one hundred+ patches series.

Yeah, right. Very much understandable. I realized you probably had more 
patches somewhere due to "Part I" designation but I couldn't check so I 
just noted the things that I came up during the review.


-- 
 i.

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