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Date: Tue, 13 Mar 2018 15:00:13 -0500
From: Eddie James <eajames@...ux.vnet.ibm.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
jdelvare@...e.com, joel@....id.au,
Christopher Bostic <cbostic@...ux.vnet.ibm.com>,
Andrew Jeffery <andrew@...id.au>
Subject: Re: [PATCH 2/2] hwmon: (ucd9000) Add debugfs attributes to provide
mfr_status
On 03/13/2018 02:29 PM, Guenter Roeck wrote:
> On Tue, Mar 13, 2018 at 02:01:51PM -0500, Eddie James wrote:
>>
>> On 03/10/2018 10:50 AM, Guenter Roeck wrote:
>>> On 03/09/2018 11:19 AM, Eddie James wrote:
>>>> From: Christopher Bostic <cbostic@...ux.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@...ux.vnet.ibm.com>
>>>> Signed-off-by: Andrew Jeffery <andrew@...id.au>
>>>> Signed-off-by: Eddie James <eajames@...ux.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 can't exactly follow your logic. You mean it is acceptable for the user to
> have to look into the datasheet to find out what the 1/2/4 byte hex value means,
> but it is unacceptable to expect the user to have to use the datasheet to
> identify what a 1..5 byte hex string, displayed in the order received from the
> chip, means ? I am having difficulties understanding the difference. How is
> 12345678 different from, say, 12 34 56 78 (which you could display as 12345678
> as well) ?
Yea, it's not different at all. Sorry, I wasn't very clear, when I said
"interpret," I meant "figure out the endian swapping," so my proposal
would display 78563412, so the user can directly use the value. I
typically expect the kernel to provide data through interfaces in host
endian, but displaying it as-received is fine as well. User can figure
it out.
V2 incoming.
Thanks,
Eddie
>
> The macro generates the file operations as part of the define, so I don't see
> having to define as valid argument. One could instead add a generic debugfs
> macro to display a string if that is of interest.
>
>> 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?
>>
> Personally I don't see a problem displaying data as received. Either case, there
> are functions/macros to convert from big/little endian to host byte order, so
> related ifdefs in the code should never be necessary.
>
> Guenter
>
>> 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 */
>>>>
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