Messages in this thread | | | Date | Tue, 27 Oct 2015 19:47:11 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH v2 1/2] hwmon: ina2xx: convert driver to using regmap |
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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@baylibre.com> > --- > > v2: > - 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.
Thanks, Guenter
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