Re: [PATCH v3 3/4] staging: rtl8723bs: use ether_addr_copy() in rtw_macaddr_cfg()

[Michael Straube]

Am 27.06.2018 um 10:33 schrieb Dan Carpenter:
> On Tue, Jun 26, 2018 at 10:32:09PM +0200, Michael Straube wrote:
> > On 06/26/18 22:17, Joe Perches wrote:
> > > On Tue, 2018-06-26 at 21:44 +0200, Michael Straube wrote:
> > > > On 06/26/18 19:32, Andy Shevchenko wrote:
> > > > > On Tue, Jun 26, 2018 at 11:14 AM, Michael Straube
> > > > > <straube.linux@xxxxxxxxx> wrote:
> > > > > > Use ether_addr_copy() instead of memcpy() to copy the mac address.
> > > > >
> > > > > Suggested-by ?
> > > >
> > > > I'll add it. Sorry, I was not aware of the Suggested-by tag.
> > > >
> > > > > Btw, ensure that the source and destination buffers are aligned to u16
> > > > > as required by API.
> > > >
> > > > To be honest I'm not sure how to do that excactly.
> > > >
> > > > Use __align(2) in the array declarations? e.g.:
> > > >
> > > >            u8 mac[ETH_ALEN] __align(2);
> > >
> > > All initial function automatics are naturally aligned.
> > > >
> > So there is nothing to change? Now I'm confused.
>
> Do not add the __align(2), as Joe says, it's not required.  You just
> need to C alignment rules (it's expected/required for this sort of
> patch).
>
> Like if you have a struct:
>
> struct foo {
> 	char a;
> 	int b;
> };
>
> There is going to be a 3 byte gap between a and b because ints are
> normally __align(4).  The exception is when the struct is __packed.  So
> sizeof(struct foo) in this case is going to be 8.  kmalloc() returns
> pointers which are 8 at least byte aligned normally.  See
> ARCH_KMALLOC_MINALIGN.  There is one arch where it's 4 byte aligned?
>
> So when you would get things which aren't __align(2) is when you have:
>
> struct bar {
> 	char a[3];
> 	u8 mac[ETH_ALEN];
> };
>
> Here the struct member before the mac[] is an odd number of char.  Or
> when the struct is packed.
>
> regards,
> dan carpenter

Thank you for your explanation. I will not add __aligned(2).
The other buffer is u32 aligned:

struct eeprom_priv
{
        u8 bautoload_fail_flag;
        u8 bloadfile_fail_flag;
        u8 bloadmac_fail_flag;
        u8 EepromOrEfuse;

        u8 mac_addr[6]; /* PermanentAddress */

	...

        u32     ocr;

	...
};

Should I add a thanks line to the commit message:

    Thanks to Dan Carpenter, Joe Perches and Andy Shevchenko.

Or would that be considered as too much?

Regards
Michael