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Message-ID: <20170713151044.GA21571@roeck-us.net>
Date: Thu, 13 Jul 2017 08:10:44 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>
Cc: zbr@...emap.net, linux-kernel@...r.kernel.org, jdelvare@...e.com,
linux-hwmon@...r.kernel.org
Subject: Re: [linux,v2,3/3] drivers: w1: add hwmon temp support for w1_therm
On Wed, Jul 12, 2017 at 02:41:18PM -0700, Jaghathiswari Rankappagounder Natarajan wrote:
> This change adds hwmon temp support for w1_therm.
>
> Signed-off-by: Jaghathiswari Rankappagounder Natarajan <jaghu@...gle.com>
> Acked-by: Evgeniy Polyakov <zbr@...emap.net>
> ---
> v2
> - make changes to support hwmon_device_register_with_info mentioned by Guenter.
>
> drivers/w1/slaves/w1_therm.c | 117 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 117 insertions(+)
>
> --
> 2.13.2.932.g7449e964c-goog
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
> diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
> index 88f4cc8c3908..147f9dfa13de 100644
> --- a/drivers/w1/slaves/w1_therm.c
> +++ b/drivers/w1/slaves/w1_therm.c
> @@ -29,6 +29,7 @@
> #include <linux/types.h>
> #include <linux/slab.h>
> #include <linux/delay.h>
> +#include <linux/hwmon.h>
>
> #include "../w1.h"
> #include "../w1_int.h"
> @@ -118,19 +119,61 @@ static struct attribute *w1_ds28ea00_attrs[] = {
> &dev_attr_w1_seq.attr,
> NULL,
> };
> +
> ATTRIBUTE_GROUPS(w1_therm);
> ATTRIBUTE_GROUPS(w1_ds28ea00);
>
Do you want the following code all the time, or enclose it in
IS_REACHABLE() ?
> +static umode_t w1_is_visible(const void *_data,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel);
> +
> +static int w1_read_temp(struct device *dev, u32 attr, int channel,
> + long *val);
> +
> +static int w1_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val);
> +
> +static int w1_write(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long val);
> +
Any chance you can rearrange the code to not require forward declarations ?
> +static const u32 w1_temp_config[] = {
> + HWMON_T_INPUT,
> + 0
> +};
> +
> +static const struct hwmon_channel_info w1_temp = {
> + .type = hwmon_temp,
> + .config = w1_temp_config,
> +};
> +
> +static const struct hwmon_channel_info *w1_info[] = {
> + &w1_temp,
> + NULL
> +};
> +
> +static const struct hwmon_ops w1_hwmon_ops = {
> + .is_visible = w1_is_visible,
> + .read = w1_read,
> + .write = w1_write,
> +};
> +
> +static const struct hwmon_chip_info w1_chip_info = {
> + .ops = &w1_hwmon_ops,
> + .info = w1_info,
> +};
> +
> static struct w1_family_ops w1_therm_fops = {
> .add_slave = w1_therm_add_slave,
> .remove_slave = w1_therm_remove_slave,
> .groups = w1_therm_groups,
> + .chip_info = &w1_chip_info,
> };
>
> static struct w1_family_ops w1_ds28ea00_fops = {
> .add_slave = w1_therm_add_slave,
> .remove_slave = w1_therm_remove_slave,
> .groups = w1_ds28ea00_groups,
> + .chip_info = &w1_chip_info,
> };
>
> static struct w1_family w1_therm_family_DS18S20 = {
> @@ -559,6 +602,80 @@ static ssize_t w1_slave_show(struct device *device,
> return ret;
> }
>
> +static int w1_read_temp(struct device *device, u32 attr, int channel,
> + long *val)
> +{
> + struct w1_slave *sl = dev_get_drvdata(device);
> + u8 *family_data = sl->family_data;
> + struct therm_info info;
> + int ret;
> +
> + if (!sl->family_data)
Why not use family_data here ?
> + return -ENODEV;
> +
> + /* prevent the slave from going away in sleep */
> + atomic_inc(THERM_REFCNT(family_data));
The original code increments the reference count with the bus mutex locked.
Similar, the original code only checks if family_data is NULL after locking
the bus mutex.
Are you sure this change in sequence doesn't cause race conditions ?
If this function can be called with family_data == NULL, what guarantees
that it isn't set to NULL after being checked but before the reference
count is increased (or, in other words, that the atomic_inc() doesn't
increment a reference counter in freed memory) ?
> +
> + switch (attr) {
> + case hwmon_temp_input:
indentation below is off.
> + ret = read_therm(device, sl, &info);
> + if (ret)
> + goto dec_refcnt;
> +
> + if (!info.verdict) {
> + dev_warn(device, "Read failed CRC check\n");
I personally dislike such noise. Personal preference, of course.
> + ret = -EIO;
> + goto dec_refcnt;
> + }
> +
> + *val = w1_convert_temp(info.rom, sl->family->fid);
> + ret = 0;
> + break;
> + default:
> + ret = -EOPNOTSUPP;
> + break;
> + }
> +
> +dec_refcnt:
> + atomic_dec(THERM_REFCNT(family_data));
> + return ret;
> +}
> +
> +static umode_t w1_is_visible(const void *_data, enum hwmon_sensor_types type,
> + u32 attr, int channel)
> +{
> + umode_t mode = 0444;
> +
> + switch (attr) {
> + case hwmon_temp_input:
> + break;
> + default:
> + mode = 0;
> + break;
> + }
> + return mode;
return attr == hwmon_temp_input ? 0444 : 0;
would be a bit simpler here.
> +}
> +
> +static int w1_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + switch (type) {
> + case hwmon_temp:
> + return w1_read_temp(dev, attr, channel, val);
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> +static int w1_write(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long val)
You don't need a write function, since attributes are never writeable.
> +{
> + switch (type) {
> + default:
> + return -EOPNOTSUPP;
> + }
> +}
> +
> #define W1_42_CHAIN 0x99
> #define W1_42_CHAIN_OFF 0x3C
> #define W1_42_CHAIN_OFF_INV 0xC3
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