[PATCH v6 4/5] nvmem: eeprom: at25: export FRAM serial num

[Jiri Prchal <jiri.prchal@aksignal.cz>]

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
0000a43644f2ae6c

Signed-off-by: Jiri Prchal <jiri.prchal@aksignal.cz>
---
v2: no change here
v3: resend and added more recipients
v4: resend
v5: reworked up on Greg comments: no spaces in string, sysfs done correctly
v6: no change here
---
 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 45a486994828..4e4fa8d3ba5d 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -39,6 +39,7 @@ 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 */
@@ -173,6 +174,25 @@ 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 = FM25_SN_LEN - 1; i >= 0; i--)
+		buf += sprintf(buf, "%02x", at25->sernum[i]);
+	sprintf(buf, "\n");
+	return (2 * FM25_SN_LEN + 1);
+}
+static DEVICE_ATTR(sernum, 0440, sernum_show, NULL);
+
+static struct attribute *sernum_attrs[] = {
+	&dev_attr_sernum.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(sernum);
+
 static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count)
 {
 	struct at25_data *at25 = priv;
@@ -417,8 +437,13 @@ 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;
 
@@ -472,6 +497,7 @@ static struct spi_driver at25_driver = {
 	.driver = {
 		.name		= "at25",
 		.of_match_table = at25_of_match,
+		.dev_groups	= sernum_groups,
 	},
 	.probe		= at25_probe,
 };
-- 
2.25.1