linux-kernel - Re: [PATCH 1/1] Fonts: font_acorn_8x8: Replace discarded const qualifier

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Message-ID: <20201102103031.GL1551@shell.armlinux.org.uk>
Date:   Mon, 2 Nov 2020 10:30:31 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     daniel.vetter@...ll.ch, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org, gregkh@...uxfoundation.org,
        yepeilin.cs@...il.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] Fonts: font_acorn_8x8: Replace discarded const
 qualifier

On Mon, Nov 02, 2020 at 10:23:43AM +0000, Russell King - ARM Linux admin wrote:
> On Sun, Nov 01, 2020 at 01:11:22PM +0000, Lee Jones wrote:
> > On Sat, 31 Oct 2020, Russell King - ARM Linux admin wrote:
> > 
> > > On Fri, Oct 30, 2020 at 06:18:22PM +0000, Lee Jones wrote:
> > > > Commit 09e5b3fd5672 ("Fonts: Support FONT_EXTRA_WORDS macros for
> > > 
> > > Your commit ID does not exist in mainline kernels, which makes this
> > > confusing. The commit ID you should be using is 6735b4632def.
> > 
> > Ah yes, quite right.  That is the ID from android-3.18 where this
> > issue was first seen and fixed against.  I will fix it up for
> > Mainline.
> > 
> > Does the fix look okay to you though Russell?
> 
> Frankly, I don't know. Looking at the commit itself, it looks safe,
> but it depends what this "extra" data is being used for. From what
> I can see, the commit in question just adds the additional opaque
> data as a member named "extra", and one is left to guess what it's
> use as.
> 
> I'd have thought a small structure with named members would have
> been the minimum given our standards for in-kernel code.
> 
> Why was the "const" dropped in the first place? Does this "extra"
> member get written to somewhere?
> 
> So, sorry, no idea. This looks to me like a very unsatisfactory
> commit, and probably something that got a very poor review.

Also, the commit description is missing a chunk:

    For user-provided fonts, the framebuffer layer resolves this issue by
    reserving four extra words at the beginning of data buffers. Later,
    whenever a function needs to access them, it simply uses the following
    macros:

    Recently we have gathered all the above macros to <linux/font.h>.

So what were these macros that have been nicely removed from the commit
description? I guess they started with a '#' character and git thought
they were a comment.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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