Message-ID: <20130715185727.4ebde8c4@endymion.delvare>
Date:	Mon, 15 Jul 2013 18:57:27 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Wei Ni <wni@...dia.com>, Guenter Roeck <linux@...ck-us.net>
Cc:	<thierry.reding@...il.com>, <lm-sensors@...sensors.org>,
	<linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] hwmon: (lm90) use macro defines for the status
 bit

Hi Wei, Guenter,

On Fri, 12 Jul 2013 15:48:05 +0800, Wei Ni wrote:
> Add bit defines for the status register.

Regarding the subject: for me these are constants, not macros. AFAIK
the term "macro" refers to defines with parameters only.

> Signed-off-by: Wei Ni <wni@...dia.com>
> ---
>  drivers/hwmon/lm90.c |   72 ++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 49 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
> index 5f30f90..c90037f 100644
> --- a/drivers/hwmon/lm90.c
> +++ b/drivers/hwmon/lm90.c
> @@ -179,6 +179,19 @@ enum chips { lm90, adm1032, lm99, lm86, max6657, max6659, adt7461, max6680,
>  #define LM90_HAVE_TEMP3		(1 << 6) /* 3rd temperature sensor	*/
>  #define LM90_HAVE_BROKEN_ALERT	(1 << 7) /* Broken alert		*/
>  
> +/* LM90 status */
> +#define LM90_STATUS_LTHRM	(1 << 0) /* local THERM limit tripped */
> +#define LM90_STATUS_RTHRM	(1 << 1) /* remote THERM limit tripped */
> +#define LM90_STATUS_OPEN	(1 << 2) /* remote is an open circuit */
> +#define LM90_STATUS_RLOW	(1 << 3) /* remote low temp limit tripped */
> +#define LM90_STATUS_RHIGH	(1 << 4) /* remote high temp limit tripped */
> +#define LM90_STATUS_LLOW	(1 << 5) /* local low temp limit tripped */
> +#define LM90_STATUS_LHIGH	(1 << 6) /* local high temp limit tripped */
> +#define LM90_STATUS_BUSY	(1 << 7) /* ADC is converting */

LM90_STATUS_BUSY is never used anywhere so please don't define it.

> +
> +#define MAX6696_STATUS2_RLOW	(1 << 3) /* remote2 low temp limit tripped */
> +#define MAX6696_STATUS2_RHIGH	(1 << 4) /* remote2 high temp limit tripped */
> +
>  /*
>   * Driver data (common to all clients)
>   */
> @@ -1417,6 +1430,36 @@ static void lm90_init_client(struct i2c_client *client)
>  		i2c_smbus_write_byte_data(client, LM90_REG_W_CONFIG1, config);
>  }
>  
> +static bool lm90_is_tripped(struct i2c_client *client)
> +{
> +	struct lm90_data *data = i2c_get_clientdata(client);
> +	u8 status, status2 = 0;
> +
> +	lm90_read_reg(client, LM90_REG_R_STATUS, &status);
> +
> +	if (data->kind == max6696)
> +		lm90_read_reg(client, MAX6696_REG_R_STATUS2, &status2);
> +
> +	if ((status & 0x7f) == 0 && (status2 & 0xfe) == 0)
> +		return false;

It's a bit disappointing to not use the freshly introduced constants.
That being said I agree it would make the code hard to read, so you can
leave it as is.

Unrelated to this patch, but Guenter, I am worried about the MAX6696
handling here. I realize that I am the one who accepted your code, but
now it looks wrong. Specifically:
* We check for (status2 & 0xfe) i.e. 7 alarm bits, but the code below
  only reports 2 alarms bits. So if any of the 5 other alarm bits in
  STATUS2 are, we may return true (chip is tripped) but not print the
  cause.
* At least bits 1 and 2 of STATUS 2 fit totally fine in the driver as
  it currently exists, so I can't think of any reason for not handling
  them. Why are we not? Ideally we should print a message for every
  alarm bit so that we never return "true" without printing a message.
  Even though OT2 limits aren't handled by the driver...
* If you think this piece of code shouldn't deal with OT/THERM limits
  because they do not trigger an SMBus alarm, this can be discussed,
  but all chips should be handled the same in this respect then.
* Why in the first place is max6696's data->alert_alarms set to 0x187c
  and not 0x1c7c? Including 1OPEN but not 2OPEN makes no sense.

> +
> +	if (status & (LM90_STATUS_LLOW | LM90_STATUS_LHIGH | LM90_STATUS_LTHRM))
> +		dev_warn(&client->dev,
> +			 "temp%d out of range, please check!\n", 1);
> +	if (status & (LM90_STATUS_RLOW | LM90_STATUS_RHIGH | LM90_STATUS_RTHRM))
> +		dev_warn(&client->dev,
> +			 "temp%d out of range, please check!\n", 2);
> +	if (status & LM90_STATUS_OPEN)
> +		dev_warn(&client->dev,
> +			 "temp%d diode open, please check!\n", 2);
> +
> +	if (status2 & (MAX6696_STATUS2_RLOW | MAX6696_STATUS2_RHIGH))
> +		dev_warn(&client->dev,
> +			 "temp%d out of range, please check!\n", 3);
> +
> +	return true;
> +}
> +
>  static int lm90_probe(struct i2c_client *client,
>  		      const struct i2c_device_id *id)
>  {
> @@ -1515,36 +1558,19 @@ static int lm90_remove(struct i2c_client *client)
>  
>  static void lm90_alert(struct i2c_client *client, unsigned int flag)
>  {
> -	struct lm90_data *data = i2c_get_clientdata(client);
> -	u8 config, alarms, alarms2 = 0;
> -
> -	lm90_read_reg(client, LM90_REG_R_STATUS, &alarms);
> -
> -	if (data->kind == max6696)
> -		lm90_read_reg(client, MAX6696_REG_R_STATUS2, &alarms2);
> -
> -	if ((alarms & 0x7f) == 0 && (alarms2 & 0xfe) == 0) {
> +	if (!lm90_is_tripped(client)) {

You could swap the success and failure cases to avoid this negation.

>  		dev_info(&client->dev, "Everything OK\n");
>  	} else {
> -		if (alarms & 0x61)
> -			dev_warn(&client->dev,
> -				 "temp%d out of range, please check!\n", 1);
> -		if (alarms & 0x1a)
> -			dev_warn(&client->dev,
> -				 "temp%d out of range, please check!\n", 2);
> -		if (alarms & 0x04)
> -			dev_warn(&client->dev,
> -				 "temp%d diode open, please check!\n", 2);
> -
> -		if (alarms2 & 0x18)
> -			dev_warn(&client->dev,
> -				 "temp%d out of range, please check!\n", 3);
> -
>  		/*
>  		 * Disable ALERT# output, because these chips don't implement
>  		 * SMBus alert correctly; they should only hold the alert line
>  		 * low briefly.
>  		 */
> +		struct lm90_data *data = i2c_get_clientdata(client);
> +		u8 config, alarms;
> +
> +		lm90_read_reg(client, LM90_REG_R_STATUS, &alarms);

You end up reading LM90_REG_R_STATUS, which is not OK. This register
contains self-clearing bits, so there is no guarantee that the second
read will return the same value as the first read. You'll have to come
up with a different approach that reads LM90_REG_R_STATUS only once.

> +
>  		if ((data->flags & LM90_HAVE_BROKEN_ALERT)
>  		 && (alarms & data->alert_alarms)) {
>  			dev_dbg(&client->dev, "Disabling ALERT#\n");


-- 
Jean Delvare
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists