[PATCH v3 4/4] nvmem: eeprom: at25: export FRAM serial num

[Jiri Prchal]

This exports serial number of FRAM in sysfs file named "sernum".
Formatted in hex, each byte separated by space.
Example:
$ cat /sys/class/spi_master/spi0/spi0.0/sernum
a4 36 44 f2 ae 6c 00 00

Signed-off-by: Jiri Prchal <jiri.prc...@aksignal.cz>
---
 drivers/misc/eeprom/at25.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index 4f6e983c278b..b2cffeb3af2c 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -38,6 +38,7 @@ struct at25_data {
        struct nvmem_config     nvmem_config;
        struct nvmem_device     *nvmem;
        int has_sernum;
+       char *sernum;
 };
 
 #define        AT25_WREN       0x06            /* latch the write enable */
@@ -172,6 +173,19 @@ static int fm25_aux_read(struct at25_data *at25, char 
*buf, uint8_t command,
        return status;
 }
 
+static ssize_t sernum_show(struct device *dev, struct device_attribute *attr, 
char *buf)
+{
+       struct at25_data *at25;
+       int i;
+
+       at25 = dev_get_drvdata(dev);
+       for (i = 0; i < FM25_SN_LEN; i++)
+               buf += sprintf(buf, "%02x ", at25->sernum[i]);
+       sprintf(--buf, "\n");
+       return (3 * i);
+}
+static DEVICE_ATTR_RO(sernum);
+
 static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
 {
        struct at25_data *at25 = priv;
@@ -427,8 +441,13 @@ static int at25_probe(struct spi_device *spi)
                else
                        at25->chip.flags |= EE_ADDR2;
 
-               if (id[8])
+               if (id[8]) {
                        at25->has_sernum = 1;
+                       at25->sernum = kzalloc(FM25_SN_LEN, GFP_KERNEL);
+                       if (!at25->sernum)
+                               return -ENOMEM;
+                       fm25_aux_read(at25, at25->sernum, FM25_RDSN, 
FM25_SN_LEN);
+               }
                else
                        at25->has_sernum = 0;
 
@@ -467,6 +486,13 @@ static int at25_probe(struct spi_device *spi)
        if (IS_ERR(at25->nvmem))
                return PTR_ERR(at25->nvmem);
 
+       /* Export the FM25 serial number */
+       if (at25->has_sernum) {
+               err = device_create_file(&spi->dev, &dev_attr_sernum);
+               if (err)
+                       return err;
+       }
+
        dev_info(&spi->dev, "%d %s %s %s%s, pagesize %u\n",
                 (chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 
1024),
                 (chip.byte_len < 1024) ? "Byte" : "KByte",
-- 
2.25.1