Re: [PATCH] net: dsa: sja1105: Remove unneeded cast in sja1105_crc32()

[Vladimir Oltean]

On Tue, Feb 23, 2021 at 12:20:03PM +0100, Geert Uytterhoeven wrote:
> sja1105_unpack() takes a "const void *buf" as its first parameter, so
> there is no need to cast away the "const" of the "buf" variable before
> calling it.
> 
> Drop the cast, as it prevents the compiler performing some checks.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> ---

Reviewed-by: Vladimir Oltean <olteanv@xxxxxxxxx>

By the way, your email went straight to my spam box, I just found the
patch by mistake on patchwork.

    Why is this message in spam?
    It is in violation of Google's recommended email sender guidelines.

> Compile-tested only.
> 
> BTW, sja1105_packing() and packing() are really bad APIs, as the input
> pointer parameters cannot be const due to the direction depending on
> "op".  This means the compiler cannot do const checks.  Worse, callers
> are required to cast away constness to prevent the compiler from
> issueing warnings.  Please don't do this!
> ---

What const checks can the compiler not do?
Also, if you know of an existing kernel API which can replace packing(),
I'm all ears.