linux-kernel - Re: [PATCH v7 1/1] gpio: add sloppy logic analyzer using polling

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Message-ID: <YkGn6/B4XHhb72YC@ninjato>
Date:   Mon, 28 Mar 2022 14:19:55 +0200
From:   Wolfram Sang <wsa+renesas@...g-engineering.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v7 1/1] gpio: add sloppy logic analyzer using polling

> > I don't like assigning 'priv' memebers twice, so I'd like to keep it as
> > is.
> 
> But this will give better understanding of the steps the code performs, no?

IMO the current version is readable :)

> (Because this function basically contains two steps at once. I assume it's
>  done this way due to absence of vrealloc(), right?)
> 
> But we have kvrealloc(). Can it be used here?

This has a huge disadvantage: realloc() requests new memory before the
old one is discarded. If you want to make a huge buffer bigger, this can
lead to OOM. The old contents do not matter, so the old buffer can go
away in favor of the new one.

> > > Can it be wrapped by DEFINE_SHOW_ATTRIBUTE()?
> > 
> > I don't see a way. Do you?
> 
> Me neither. I mixed this up with (not upstreamed yet) DEFINE_STORE_ATTRIBUTE.

Still no cigar. That one is for rw files. Mine is writable only, so I use
e.g. no_llseek.

Probably, the above macro should be named, DEFINE_SHOWSTORE_ATTRIBUTE.
But I see this macro is stalled since late 2020 anyhow.

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