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SubjectRe: [PATCH 02/17] coresight tmc: Hide trace buffer handling for file read
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Hi Suzuki,

On 19/10/17 18:15, Suzuki K Poulose wrote:
> At the moment we adjust the buffer pointers for reading the trace
> data via misc device in the common code for ETF/ETB and ETR. Since
> we are going to change how we manage the buffer for ETR, let us
> move the buffer manipulation to the respective driver files, hiding
> it from the common code. We do so by adding type specific helpers
> for finding the length of data and the pointer to the buffer,
> for a given length at a file position.
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 16 ++++++++++++
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 33 ++++++++++++++++++++++++
> drivers/hwtracing/coresight/coresight-tmc.c | 34 ++++++++++++++-----------
> drivers/hwtracing/coresight/coresight-tmc.h | 4 +++
> 4 files changed, 72 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index e2513b786242..0b6f1eb746de 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -120,6 +120,22 @@ static void tmc_etf_disable_hw(struct tmc_drvdata *drvdata)
> CS_LOCK(drvdata->base);
> }
>
> +/*
> + * Return the available trace data in the buffer from @pos, with
> + * a maximum limit of @len, updating the @bufpp on where to
> + * find it.
> + */
> +ssize_t tmc_etb_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + /* Adjust the len to available size @pos */
> + if (pos + len > drvdata->len)
> + len = drvdata->len - pos;
> + if (len > 0)

Do we have some guarantee that "pos <= drvdata->len"? because since len
is unsigned this check only covers the case were len is 0.

Maybe it would be better to use a signed variable to store the result of
the difference.

> + *bufpp = drvdata->buf + pos;
> + return len;
> +}
> +
> static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev)
> {
> int ret = 0;
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index d0208f01afd9..063f253f1c99 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -69,6 +69,39 @@ static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
> CS_LOCK(drvdata->base);
> }
>
> +/*
> + * Return the available trace data in the buffer @pos, with a maximum
> + * limit of @len, also updating the @bufpp on where to find it.
> + */
> +ssize_t tmc_etr_get_sysfs_trace(struct tmc_drvdata *drvdata,
> + loff_t pos, size_t len, char **bufpp)
> +{
> + char *bufp = drvdata->buf + pos;
> + char *bufend = (char *)(drvdata->vaddr + drvdata->size);
> +
> + /* Adjust the len to available size @pos */
> + if (pos + len > drvdata->len)
> + len = drvdata->len - pos;
> +
> + if (len <= 0)
> + return len;

Similar issue here.

Cheers,

--
Julien Thierry

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