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Subject: Re: [PATCH 2/2] hwmon: (ucd9000) Add debugfs attributes to provide
 mfr_status
To:     Guenter Roeck <linux@roeck-us.net>, linux-hwmon@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, jdelvare@suse.com, joel@jms.id.au,
        Christopher Bostic <cbostic@linux.vnet.ibm.com>,
        Andrew Jeffery <andrew@aj.id.au>
References: <1520623196-9534-1-git-send-email-eajames@linux.vnet.ibm.com>
 <1520623196-9534-3-git-send-email-eajames@linux.vnet.ibm.com>
 <cedded07-3b6d-1b1f-573b-3790a52e1700@roeck-us.net>
From:   Eddie James <eajames@linux.vnet.ibm.com>
Date:   Tue, 13 Mar 2018 14:01:51 -0500
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On 03/10/2018 10:50 AM, Guenter Roeck wrote:
> On 03/09/2018 11:19 AM, Eddie James wrote:
>> From: Christopher Bostic <cbostic@linux.vnet.ibm.com>
>>
>> Expose the gpiN_fault fields of mfr_status as individual debugfs
>> attributes. This provides a way for users to be easily notified of gpi
>> faults. Also provide the whole mfr_status register in debugfs.
>>
>> Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com>
>> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
>> Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
>> ---
>>   drivers/hwmon/pmbus/ucd9000.c | 172 
>> +++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 171 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hwmon/pmbus/ucd9000.c 
>> b/drivers/hwmon/pmbus/ucd9000.c
>> index e3a507f..297da0e 100644
>> --- a/drivers/hwmon/pmbus/ucd9000.c
>> +++ b/drivers/hwmon/pmbus/ucd9000.c
>> @@ -19,6 +19,7 @@
>>    * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>>    */
>>   +#include <linux/debugfs.h>
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/of_device.h>
>> @@ -36,6 +37,7 @@
>>   #define UCD9000_NUM_PAGES        0xd6
>>   #define UCD9000_FAN_CONFIG_INDEX    0xe7
>>   #define UCD9000_FAN_CONFIG        0xe8
>> +#define UCD9000_MFR_STATUS        0xf3
>>   #define UCD9000_GPIO_SELECT        0xfa
>>   #define UCD9000_GPIO_CONFIG        0xfb
>>   #define UCD9000_DEVICE_ID        0xfd
>> @@ -63,13 +65,22 @@
>>   #define UCD901XX_NUM_GPIOS    26
>>   #define UCD90910_NUM_GPIOS    26
>>   +#define UCD9000_DEBUGFS_NAME_LEN    24
>> +#define UCD9000_GPI_COUNT        8
>> +
>>   struct ucd9000_data {
>>       u8 fan_data[UCD9000_NUM_FAN][I2C_SMBUS_BLOCK_MAX];
>>       struct pmbus_driver_info info;
>>       struct gpio_chip gpio;
>> +    struct dentry *debugfs;
>>   };
>>   #define to_ucd9000_data(_info) container_of(_info, struct 
>> ucd9000_data, info)
>>   +struct ucd9000_debugfs_entry {
>> +    struct i2c_client *client;
>> +    u8 index;
>> +};
>> +
>>   static int ucd9000_get_fan_config(struct i2c_client *client, int fan)
>>   {
>>       int fan_config = 0;
>> @@ -328,6 +339,156 @@ static int ucd9000_gpio_direction_output(struct 
>> gpio_chip *gc,
>>                         val);
>>   }
>>   +#if IS_ENABLED(CONFIG_DEBUG_FS)
>> +static int ucd9000_get_mfr_status(struct i2c_client *client, u8 
>> *buffer)
>> +{
>> +    int ret = pmbus_set_page(client, 0);
>> +
>> +    if (ret < 0)
>> +        return ret;
>> +
>> +    /*
>> +     * With the ucd90120 and ucd90124 devices, this command 
>> [MFR_STATUS]
>> +     * is 2 bytes long (bits 0-15).  With the ucd90240 this command 
>> is 5
>> +     * bytes long.  With all other devices, it is 4 bytes long.
>> +     */
>> +    return i2c_smbus_read_block_data(client, UCD9000_MFR_STATUS, 
>> buffer);
>> +}
>> +
>> +static int ucd9000_debugfs_show_mfr_status_bit(void *data, u64 *val)
>> +{
>> +    struct ucd9000_debugfs_entry *entry = data;
>> +    struct i2c_client *client = entry->client;
>> +    u8 buffer[4];
>> +    int ret;
>> +
>> +    /*
>> +     * This attribute is only created for devices that return 4 
>> bytes for
>> +     * status_mfr, so it's safe to call with 4-byte buffer.
>> +     */
>> +    ret = ucd9000_get_mfr_status(client, buffer);
>> +    if (ret < 0) {
>> +        dev_err(&client->dev, "Failed to read mfr status. rc:%d\n",
>> +            ret);
>> +
>> +        return ret;
>> +    }
>> +
>> +    /*
>> +     * Attribute only created for devices with gpi fault bits at bits
>> +     * 16-23, which is the second byte of the response.
>> +     */
>> +    *val = !!(buffer[1] & BIT(entry->index));
>> +
>> +    return 0;
>> +}
>> +DEFINE_DEBUGFS_ATTRIBUTE(ucd9000_debugfs_mfr_status_bit,
>> +             ucd9000_debugfs_show_mfr_status_bit, NULL, "%1lld\n");
>> +
>> +static int ucd9000_debugfs_show_mfr_status_word2(void *data, u64 *val)
>> +{
>> +    struct i2c_client *client = data;
>> +    __be16 buffer;
>> +    int ret;
>> +
>> +    ret = ucd9000_get_mfr_status(client, (u8 *)&buffer);
>> +    if (ret < 0) {
>> +        dev_err(&client->dev, "Failed to read mfr status. rc:%d\n",
>> +            ret);
>> +
>> +        return ret;
>> +    }
>> +
>> +    *val = be16_to_cpu(buffer);
>> +
>> +    return 0;
>> +}
>> +DEFINE_DEBUGFS_ATTRIBUTE(ucd9000_debugfs_mfr_status_word2,
>> +             ucd9000_debugfs_show_mfr_status_word2, NULL,
>> +             "%04llx\n");
>> +
>> +static int ucd9000_debugfs_show_mfr_status_word4(void *data, u64 *val)
>> +{
>> +    struct i2c_client *client = data;
>> +    __be32 buffer;
>> +    int ret;
>> +
>> +    ret = ucd9000_get_mfr_status(client, (u8 *)&buffer);
>> +    if (ret < 0) {
>> +        dev_err(&client->dev, "Failed to read mfr status. rc:%d\n",
>> +            ret);
>> +
>> +        return ret;
>> +    }
>> +
>> +    *val = be32_to_cpu(buffer);
>> +
>> +    return 0;
>> +}
>> +DEFINE_DEBUGFS_ATTRIBUTE(ucd9000_debugfs_mfr_status_word4,
>> +             ucd9000_debugfs_show_mfr_status_word4, NULL,
>> +             "%08llx\n");
>> +
>> +static int ucd9000_init_debugfs(struct i2c_client *client,
>> +                const struct i2c_device_id *mid,
>> +                struct ucd9000_data *data)
>> +{
>> +    struct dentry *debugfs;
>> +    struct ucd9000_debugfs_entry *entries;
>> +    int i;
>> +    char name[UCD9000_DEBUGFS_NAME_LEN];
>> +
>> +    debugfs = pmbus_get_debugfs_dir(client);
>> +    if (!debugfs)
>> +        return -ENOENT;
>> +
>> +    data->debugfs = debugfs_create_dir(client->name, debugfs);
>> +    if (!data->debugfs)
>> +        return -ENOENT;
>> +
>> +    /*
>> +     * Of the chips this driver supports, only the UCD9090, UCD90160,
>> +     * and UCD90910 report GPI faults in their MFR_STATUS register, 
>> so only
>> +     * create the GPI fault debugfs attributes for those chips.
>> +     */
>> +    if (mid->driver_data == ucd9090 || mid->driver_data == ucd90160 ||
>> +        mid->driver_data == ucd90910) {
>> +        entries = devm_kzalloc(&client->dev,
>> +                       sizeof(*entries) * UCD9000_GPI_COUNT,
>> +                       GFP_KERNEL);
>> +        if (!entries)
>> +            return -ENOMEM;
>> +
>> +        for (i = 0; i < UCD9000_GPI_COUNT; i++) {
>> +            entries[i].client = client;
>> +            entries[i].index = i;
>> +            scnprintf(name, UCD9000_DEBUGFS_NAME_LEN,
>> +                  "gpi%d_alarm", i + 1);
>> +            debugfs_create_file(name, 0444, data->debugfs,
>> +                        &entries[i],
>> +                        &ucd9000_debugfs_mfr_status_bit);
>> +        }
>> +
>> +        scnprintf(name, UCD9000_DEBUGFS_NAME_LEN, "mfr_status");
>> +        debugfs_create_file(name, 0444, data->debugfs, client,
>> +                    &ucd9000_debugfs_mfr_status_word4);
>> +    } else if (mid->driver_data == ucd90120 ||
>> +           mid->driver_data == ucd90124) {
>> +        scnprintf(name, UCD9000_DEBUGFS_NAME_LEN, "mfr_status");
>> +        debugfs_create_file(name, 0444, data->debugfs, client,
>> +                    &ucd9000_debugfs_mfr_status_word2);
>> +    }
>> +
>> +    return 0;
>> +}
>
> Is all that complexity really worth it ? Why not just read the 
> manufacturing
> status as byte string into a buffer and use hexdump to pront it, no 
> matter how
> many bytes are actually returned ? This would also be less error 
> prone, and
> automatically support future chips.

Hm, well then we have the additional complexity of setting up custom 
debugfs file operations to show the binary data instead of just using 
DEFINE_DEBUGFS_ATTRIBUTE. Plus, at some point someone has to interpret 
it as either a word, half-word, or 5 bytes chunk. Where better to do it 
than the driver, as this is hw-dependent?

I could just use one function and do a byte-swap based on data length in 
a loop within #ifdef LITTLE_ENDIAN, but that's a little messy. It will 
handle all the cases though. What do you think?

Thanks,
Eddie

>
> Thanks,
> Guenter
>
>> +#else
>> +static int ucd9000_init_debugfs(struct i2c_client *client,
>> +                struct ucd9000_data *data)
>> +{
>> +    return 0;
>> +}
>> +#endif /* IS_ENABLED(CONFIG_DEBUG_FS) */
>> +
>>   static int ucd9000_probe(struct i2c_client *client,
>>                const struct i2c_device_id *id)
>>   {
>> @@ -483,7 +644,16 @@ static int ucd9000_probe(struct i2c_client *client,
>>           return ret;
>>       }
>>   -    return pmbus_do_probe(client, mid, info);
>> +    ret = pmbus_do_probe(client, mid, info);
>> +    if (ret)
>> +        return ret;
>> +
>> +    ret = ucd9000_init_debugfs(client, mid, data);
>> +    if (ret)
>> +        dev_warn(&client->dev, "Failed to register debugfs: %d\n",
>> +             ret);
>> +
>> +    return 0;
>>   }
>>     /* This is the driver that will be inserted */
>>
>