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SubjectRe: [PATCH 04/11] hwmon: applesmc: Introduce a register lookup table (rev2)
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On Tue, 2010-11-09 at 10:15 -0500, Henrik Rydberg wrote:
> One main problem with the current driver is the inability to quickly
> search for supported keys, resulting in detailed feature maps per
> machine model which are cumbersome to maintain.
>
> This patch adds a register lookup table, which enables binary search
> for supported keys. The lookup also reduces the io frequency, so the
> original mutex is replaced by locks around the actual io.
>
> Signed-off-by: Henrik Rydberg <rydberg@euromail.se>

Hi Henrik,

looks pretty good now. Couple of additional comments.

> ---
> drivers/hwmon/applesmc.c | 528 +++++++++++++++++++++++++---------------------
> 1 files changed, 286 insertions(+), 242 deletions(-)
>
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index 5f67e39..623f71c 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
[ ... ]
> +/*
> + * applesmc_init_smcreg_try - Try to initialize register cache. Idempotent.
> + */
> +static int applesmc_init_smcreg_try(void)
> +{
> + struct applesmc_registers *s = &smcreg;
> + int ret;
> +
> + if (s->init_complete)
> + return 0;
> +
> + mutex_init(&s->mutex);
> +
I am a bit concerned that mutex_init() can be called multiple times. Are
you sure this is safe ?

> + ret = read_register_count(&s->key_count);
> + if (ret)
> + return ret;
> +
> + if (!s->cache)
> + s->cache = kcalloc(s->key_count, sizeof(*s->cache), GFP_KERNEL);
> + if (!s->cache)
> + return -ENOMEM;
> +
> + s->init_complete = true;
> +
> + pr_info("key=%d\n", s->key_count);
> +
Hope that means more to macbook users than it does to me ;).

> + return 0;
> +}
> +
> +/*
> + * applesmc_init_smcreg - Initialize register cache.
> + *
> + * Retries until initialization is successful, or the operation times out.
> + *
> + */
> +static int applesmc_init_smcreg(void)
> +{
> + int ms, ret;
> +
> + for (ms = 0; ms < INIT_TIMEOUT_MSECS; ms += INIT_WAIT_MSECS) {
> + ret = applesmc_init_smcreg_try();
> + if (!ret)
> + return 0;
> + pr_warn("slow init, retrying\n");

INIT_WAIT_MS is 50ms, so you issue this warning every 50ms for up to
five seconds. Pretty noisy... sure that is what you want ? Also, does it
really make sense to retry if the error is ENOMEM ?

Thanks,
Guenter




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