Re: [PATCH v4 1/1] lib/vsprintf: Add support for printing V4L2 and DRM fourccs

[Andy Shevchenko]

On Tue, Nov 03, 2020 at 04:56:16PM +0200, Sakari Ailus wrote:
> On Tue, Nov 03, 2020 at 04:47:47PM +0200, Andy Shevchenko wrote:
> > On Tue, Nov 03, 2020 at 03:34:00PM +0200, Sakari Ailus wrote:
> > > Add a printk modifier %p4cc (for pixel format) for printing V4L2 and DRM
> > > pixel formats denoted by fourccs. The fourcc encoding is the same for both
> > > so the same implementation can be used.

...

> > > +	char output[sizeof("(xx)(xx)(xx)(xx) little-endian (0x01234567)")];
> > 
> > I would add a comment that there is another possibility, i.e. big-endian, but
> > it occupies less space.
> 
> This string is here to represent the longest possible output of the
> function. Most of the time it's less. Saying that might make sense but it's
> fairly clear already. Either way works for me though.

It's not known by reading the above line. I would add a comment.

...

> > > +	p = special_hex_number(p, output + sizeof(output) - 2, *fourcc,
> > > +			       sizeof(u32));
> > 
> > I would go with one line here.
> 
> It's wrapped since the result would be over 80 otherwise.

It will be not the first one breaking the limit in this module for the sake of
readability.

...

> > The (theoretical) problem is here that the case when buffer size is not enough
> > to print a value will be like '(0xabc)' but should be rather '(0xabcd' like
> > snprintf() does in general.

Any comments here?
Perhaps you need to add a comment to explain that the overflow is impossible.

-- 
With Best Regards,
Andy Shevchenko