Re: [PATCH v2 1/2] hwmon: ina2xx: convert driver to using regmap

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On 28/10/2015 03:47, Guenter Roeck wrote:
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.

Right, I had that same afterthought when removing the mutex at that position. Fix incoming!



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