[U-Boot] [PATCH 1/1] net: avoid address-of-packed-member error

[Tom Rini]

On Mon, Nov 04, 2019 at 10:21:14PM +0100, Simon Goldschmidt wrote:
> Tom Rini <trini at konsulko.com> schrieb am Mo., 4. Nov. 2019, 22:15:
> 
> > On Mon, Nov 04, 2019 at 09:28:51PM +0100, Simon Goldschmidt wrote:
> > > Am 04.11.2019 um 20:34 schrieb Heinrich Schuchardt:
> > > > struct ip_udp_hdr is naturally packed. There is no point in adding a
> > > > __packed attribute. With the attribute the network stack does not
> > compile
> > > > using GCC 9.2.1:
> > >
> > > Is this commit message correct? In lwIP, we *do* need to pack all these
> > > network header structs as they can come in unaligned. Especially the IP
> > > header is normally 16-bit aligned if the incoming Ethernet frame is
> > 32-bit
> > > aligned (which is a must for many DMA engines).
> > >
> > > This is also the reason why the below code works, I guess: it is rarely
> > > totally unaligned, but nearly always at least 16-bit aligned, so
> > > dereferencing the checksum pointer as aligned u16 just works.
> > >
> > > Nevertheless, the code is formally wrong and your patch is correct. I
> > just
> > > don't like the commit message saying 'packed' is not required.
> >
> > Perhaps we should fix the underlying code problem then?  Or does that
> > men "rewrite the whole file" ?
> >
> 
> This patch fixes the code problem. If there are more problems: any
> assignment to an u16 pointer from an address of a packed struct issues a
> warning (provided that appropriate warning settings are used). If we fix
> all of these warnings (e.g. like we do here, by using alignment agnostic
> byte accesses), we should be good.
> 
> I just think the misleading commit message should be fixed before giving my
> RB.

Ah, I get it now I hope, thanks.

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20191104/7a5059f9/attachment.sig>