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SubjectRe: [PATCH v4 03/14] coresight: move shared barrier_pkt[] to coresight_priv.h
On Tue, Jun 05, 2018 at 04:06:59PM -0500, Kim Phillips wrote:
> barrier_pkt[] is used in the etb and tmc-etf coresight
> components. Change barrier_pkt[] to a static definition,
> so as to allow them to be built as modules.
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Leo Yan <leo.yan@linaro.org>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Russell King <linux@armlinux.org.uk>
> Signed-off-by: Kim Phillips <kim.phillips@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-priv.h | 8 +++++++-
> drivers/hwtracing/coresight/coresight.c | 7 -------
> 2 files changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 158c720119dd..e76f19ca9e04 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -57,7 +57,13 @@ static DEVICE_ATTR_RO(name)
> #define coresight_simple_reg64(type, name, lo_off, hi_off) \
> __coresight_simple_func(type, NULL, name, lo_off, hi_off)
>
> -extern const u32 barrier_pkt[4];
> +/*
> + * When losing synchronisation a new barrier packet needs to be inserted at the
> + * beginning of the data collected in a buffer. That way the decoder knows that
> + * it needs to look for another sync sequence.
> + */
> +static const u32 barrier_pkt[4] = { 0x7fffffff, 0x7fffffff,
> + 0x7fffffff, 0x7fffffff };

Are you _sure_ this is doing what you think it is doing?

You now just created a bunch of different copies of this structure,
which might change the logic involved, right?

Putting a static variable in a .h file is generally considered a very
bad thing to do, I need a lot more "proof" this is ok before I can
accept this. Worse case, just put the variable in the individual places
where it is needed.

thanks,

greg k-h

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