Re: [PATCH v2 1/2] hwmon: ina2xx: convert driver to using regmap
From: Guenter Roeck
Date: Tue Oct 27 2015 - 22:47:18 EST
On Tue, Oct 27, 2015 at 10:51:07AM +0100, Marc Titinger wrote:
> Any sysfs "show" read access from the client app will result in reading
> all registers (8 with ina226). Depending on the host this can limit the
> best achievable read rate.
> This changeset allows for individual register accesses through regmap.
> Tested with BeagleBone Black (Baylibre-ACME) and ina226.
> Signed-off-by: Marc Titinger <mtitinger@xxxxxxxxxxxx>
> - rename 'rv' to 'regval' for clarity
> - fix missed smbus_xxx api change to regmap
> - rename ina2xx_do_update to ina2xx_read_reg
> - fix indentation
> drivers/hwmon/ina2xx.c | 211 +++++++++++++++++++------------------------------
> 1 file changed, 82 insertions(+), 129 deletions(-)
> diff --git a/drivers/hwmon/ina2xx.c b/drivers/hwmon/ina2xx.c
> index 4d28150..5e7ada8 100644
> --- a/drivers/hwmon/ina2xx.c
> +++ b/drivers/hwmon/ina2xx.c
[ ... ]
> - mutex_lock(&data->update_lock);
> data->rshunt = val;
> status = ina2xx_calibrate(data);
> - mutex_unlock(&data->update_lock);
I think this can result in a race conditon if multiple processes
try to update the shunt resistor value at the same time in a
multi-core system. There is no guarantee that the value programmed
into the chip matches the value that is written into 'rshunt'.
So I think we still need the mutex, unless you have a better
idea how to avoid the race.
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