linux-kernel - Re: [PATCH 3/4] firmware: arm_scmi: Fix scmi_event

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Message-ID: <20200709082348.GA20219@e119603-lin.cambridge.arm.com>
Date:   Thu, 9 Jul 2020 09:24:04 +0100
From:   Cristian Marussi <cristian.marussi@....com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH 3/4] firmware: arm_scmi: Fix scmi_event_header fields
 typing

On Wed, Jul 08, 2020 at 10:38:08PM +0200, Arnd Bergmann wrote:
> On Wed, Jul 8, 2020 at 2:24 PM Cristian Marussi
> <cristian.marussi@....com> wrote:
> >
> > Drop size_t in favour of fixed size u32 for consistency and shuffle
> > around fields definitions to minimize implicit padding.
> >
> > Signed-off-by: Cristian Marussi <cristian.marussi@....com>
> 
> As you still have implicit padding at the end, I'd either make
> that explicit now, or leave the __packed attribute.

Do you mean expliciting that with a comment, right ? being the last member 'payld'
a flexible array must be the last in order to even compile.

I'm a bit confused anyway on how the trailing padding works on a struct like
this which ends with a flexible array definition, so I was expecting that the
trailing pads would have made no difference, given that it's used to basically
give some know layout to a blob of data via casting...

Thanks

Cristian

> 
> The payld_sz is not actually force to be misaligned with the
> reordered layout, which is what's most important.
> 
>      Arnd