Re: [PATCH] firmware: cirrus: cs_dsp: Avoid padding bytes in cs_dsp_coeff_ctl

On Mon, Apr 25, 2022 at 10:51:59AM +0100, Richard Fitzgerald wrote:

Change the order of members in struct cs_dsp_coeff_ctl to avoid the compiler having to insert alignment padding bytes. On a x86_64 build this saves 16 bytes per control.

• Pointers are collected to the top of the struct (with the exception of priv, as noted below), so that they are inherently aligned.
• The set and enable bitflags are placed together so they can be merged.
• priv is placed at the end of the struct - it is for use by the client so it is helpful to make it stand out, and since the compiler will always pad the struct size to an alignment multiple putting a pointer last won't introduce any more padding.
• struct cs_dsp_alg_region is placed at the end, right before priv, for the same reasoning as priv.

Signed-off-by: Richard Fitzgerald rf@opensource.cirrus.com

Reviewed-by: Charles Keepax ckeepax@opensource.cirrus.com

Thanks, Charles