Re: [PATCH 00/36] tty: type unifications -- part I.

[Jiri Slaby]

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.

thanks,
--
js
suse labs