Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Thu, 25 Feb 2021 08:28:15 +0100 | Subject | Re: [PATCH] net: dsa: sja1105: Remove unneeded cast in sja1105_crc32() |
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Hi Vladimir,
On Wed, Feb 24, 2021 at 11:44 PM Vladimir Oltean <olteanv@gmail.com> wrote: > 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@glider.be> > > --- > > Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Thanks!
> 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.
Yeah, sometimes Gmail can be annoying. I recommend adding a filter to never send emails with "PATCH" in the subject to spam.
> > 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?
If you have a const and a non-const buffer, and accidentally call packing() with the two buffer pointers exchanged (this is a common mistake), you won't get a compiler warning. So having separate pack() and unpack() functions would be safer. You can rename packing() to __packing() to make it clear this function is not to be called directly without deep consideration, and have pack() and unpack() as wrappers just calling __packing(). Of course that means callers that do need a separate "op" parameter still need to call __packing(), but they can provide their own safer wrappers, too.
> Also, if you know of an existing kernel API which can replace packing(), > I'm all ears.
No idea.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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