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

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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


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