Re: [PATCH v5 20/21] hwmon: (mr75203) add debugfs to read and write temperature coefficients

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On 9/13/2022 4:06 PM, Farber, Eliav wrote:
On 9/8/2022 9:11 PM, Andy Shevchenko wrote:
On Thu, Sep 08, 2022 at 03:24:48PM +0000, Eliav Farber wrote:
This change adds debugfs to read and write temperature sensor coefficients
- g, h, j and cal5.

The coefficients can vary between product and product, so it can be very
useful to be able to modify them on the fly during the calibration
process.

e.g.:

cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
4096

echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g

...

- Return j coefficient to use debugfs_create_file() instead of
  debugfs_create_u32() because j is signed.

You can use

DEFINE_DEBUGFS_ATTRIBUTE(ts_coeff_j, ts_coeff_j_get, ts_coeff_j_set, "%lld\n");

which still makes code compact.


I tried your suggestion to use DEFINE_DEBUGFS_ATTRIBUTE but I can't set
j to be a negative value:

root@alpine:~# cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_j
0
root@alpine:~# echo 100 > /sys/kernel/debug/940f23d0000.pvt/ts_coeff_j
root@alpine:~# cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_j
100
root@alpine:~# echo -100 > /sys/kernel/debug/940f23d0000.pvt/ts_coeff_j
sh: write error: Invalid argument

This is the code I added:

static int ts_coeff_j_set(void *data, u64 val)
{
    struct pvt_device *pvt = data;

    pvt->ts_coeff.j = val;
    return 0;
}

static int ts_coeff_j_get(void *data, u64 *val)
{
    struct pvt_device *pvt = data;

    *val = pvt->ts_coeff.j;
    return 0;
}

DEFINE_DEBUGFS_ATTRIBUTE(ts_coeff_j_fops, ts_coeff_j_get,
             ts_coeff_j_set, "%lld\n");

static void devm_pvt_ts_dbgfs_remove(void *data)
{
    struct pvt_device *pvt = (struct pvt_device *)data;

    debugfs_remove_recursive(pvt->dbgfs_dir);
    pvt->dbgfs_dir = NULL;
}

static int pvt_ts_dbgfs_create(struct pvt_device *pvt, struct device *dev)
{
    ...
    debugfs_create_file("ts_coeff_j", 0644, pvt->dbgfs_dir, pvt,
                &ts_coeff_j_fops);
    ...

I'm using kernel 5.10.112.
Can you please see if I'm did anything wrong?

It seems like debugfs_attr_write() calls simple_attr_write() and it uses
kstrtoull(), which is why it fails when setting a negative value.
This is the same also in v6.0-rc5.

debugfs_attr_read() on the other hand does show the correct value also
when j is negative.

--
Regards, Eliav





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