Obtained with:
$ make W=1

sound/soc/fsl/fsl_easrc.c:967:5: warning: no previous prototype for function 'fsl_easrc_config_context' [-Wmissing-prototypes]
int fsl_easrc_config_context(struct fsl_asrc *easrc, unsigned int ctx_id)
    ^
sound/soc/fsl/fsl_easrc.c:967:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_config_context(struct fsl_asrc *easrc, unsigned int ctx_id)
^
static
sound/soc/fsl/fsl_easrc.c:1128:5: warning: no previous prototype for function 'fsl_easrc_set_ctx_format' [-Wmissing-prototypes]
int fsl_easrc_set_ctx_format(struct fsl_asrc_pair *ctx,
    ^
sound/soc/fsl/fsl_easrc.c:1128:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_set_ctx_format(struct fsl_asrc_pair *ctx,
^
static
sound/soc/fsl/fsl_easrc.c:1201:5: warning: no previous prototype for function 'fsl_easrc_set_ctx_organziation' [-Wmissing-prototypes]
int fsl_easrc_set_ctx_organziation(struct fsl_asrc_pair *ctx)
    ^
sound/soc/fsl/fsl_easrc.c:1201:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_set_ctx_organziation(struct fsl_asrc_pair *ctx)
^
static
sound/soc/fsl/fsl_easrc.c:1245:5: warning: no previous prototype for function 'fsl_easrc_request_context' [-Wmissing-prototypes]
int fsl_easrc_request_context(int channels, struct fsl_asrc_pair *ctx)
    ^
sound/soc/fsl/fsl_easrc.c:1245:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_request_context(int channels, struct fsl_asrc_pair *ctx)
^
static
sound/soc/fsl/fsl_easrc.c:1290:6: warning: no previous prototype for function 'fsl_easrc_release_context' [-Wmissing-prototypes]
void fsl_easrc_release_context(struct fsl_asrc_pair *ctx)
     ^
sound/soc/fsl/fsl_easrc.c:1290:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
void fsl_easrc_release_context(struct fsl_asrc_pair *ctx)
^
static
sound/soc/fsl/fsl_easrc.c:1317:5: warning: no previous prototype for function 'fsl_easrc_start_context' [-Wmissing-prototypes]
int fsl_easrc_start_context(struct fsl_asrc_pair *ctx)
    ^
sound/soc/fsl/fsl_easrc.c:1317:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_start_context(struct fsl_asrc_pair *ctx)
^
static
sound/soc/fsl/fsl_easrc.c:1335:5: warning: no previous prototype for function 'fsl_easrc_stop_context' [-Wmissing-prototypes]
int fsl_easrc_stop_context(struct fsl_asrc_pair *ctx)
    ^
sound/soc/fsl/fsl_easrc.c:1335:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
int fsl_easrc_stop_context(struct fsl_asrc_pair *ctx)
^
static
sound/soc/fsl/fsl_easrc.c:1382:18: warning: no previous prototype for function 'fsl_easrc_get_dma_channel' [-Wmissing-prototypes]
struct dma_chan *fsl_easrc_get_dma_channel(struct fsl_asrc_pair *ctx,
                 ^
sound/soc/fsl/fsl_easrc.c:1382:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
struct dma_chan *fsl_easrc_get_dma_channel(struct fsl_asrc_pair *ctx,
^
static

Fixes: 955ac624 ("ASoC: fsl_easrc: Add EASRC ASoC CPU DAI drivers")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
Acked-by: Nicolin Chen <nicoleotsuka@gmail.com>
Link: https://lore.kernel.org/r/ab1b83a56c71f4159a98e6da5602c2c36fe59f4d.1591155860.git.shengjiu.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>