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

From: Richard Fitzgerald
Date: Mon Apr 25 2022 - 05:53:19 EST


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@xxxxxxxxxxxxxxxxxxxxx>
---
include/linux/firmware/cirrus/cs_dsp.h | 28 +++++++++++++-------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/firmware/cirrus/cs_dsp.h b/include/linux/firmware/cirrus/cs_dsp.h
index 38b4da3ddfe4..30055706cce2 100644
--- a/include/linux/firmware/cirrus/cs_dsp.h
+++ b/include/linux/firmware/cirrus/cs_dsp.h
@@ -68,36 +68,36 @@ struct cs_dsp_alg_region {

/**
* struct cs_dsp_coeff_ctl - Describes a coefficient control
+ * @list: List node for internal use
+ * @dsp: DSP instance associated with this control
+ * @cache: Cached value of the control
* @fw_name: Name of the firmware
* @subname: Name of the control parsed from the WMFW
* @subname_len: Length of subname
- * @alg_region: Logical region associated with this control
- * @dsp: DSP instance associated with this control
- * @enabled: Flag indicating whether control is enabled
- * @list: List node for internal use
- * @cache: Cached value of the control
* @offset: Offset of control within alg_region in words
* @len: Length of the cached value in bytes
- * @set: Flag indicating the value has been written by the user
- * @flags: Bitfield of WMFW_CTL_FLAG_ control flags defined in wmfw.h
* @type: One of the WMFW_CTL_TYPE_ control types defined in wmfw.h
+ * @flags: Bitfield of WMFW_CTL_FLAG_ control flags defined in wmfw.h
+ * @set: Flag indicating the value has been written by the user
+ * @enabled: Flag indicating whether control is enabled
+ * @alg_region: Logical region associated with this control
* @priv: For use by the client
*/
struct cs_dsp_coeff_ctl {
+ struct list_head list;
+ struct cs_dsp *dsp;
+ void *cache;
const char *fw_name;
/* Subname is needed to match with firmware */
const char *subname;
unsigned int subname_len;
- struct cs_dsp_alg_region alg_region;
- struct cs_dsp *dsp;
- unsigned int enabled:1;
- struct list_head list;
- void *cache;
unsigned int offset;
size_t len;
- unsigned int set:1;
- unsigned int flags;
unsigned int type;
+ unsigned int flags;
+ unsigned int set:1;
+ unsigned int enabled:1;
+ struct cs_dsp_alg_region alg_region;

void *priv;
};
--
2.30.2