Re: [PATCH] USB: ehci: use packed,aligned(4) instead of removingthe packed attribute

From: Alan Stern
Date: Thu Jun 16 2011 - 13:10:02 EST

On Thu, 16 Jun 2011, Alexander Holler wrote:

> In commit 139540170d9d9b7ead3caaf540f161756b356d56 the attribute
> packed is removed from the structs which are used to access the EHCI-registers.
> This is done to circumvent a problem with gcc 4.6, which might access members of
> packed structs on a byte by byte basis. But using packed, aligned(4) fixes that
> too and is imho the better solution. Otherwise (without packed) the compiler would be free
> to choose whatever alignment he thinks fits best, which might be e.g. 8-byte on 64-bit machines.

Is that really true? I thought the compiler was not allowed to insert
padding if the natural alignment of the data types didn't require any.

Alan Stern

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