[PATCH v4 16/21] misc: support for writing to LP-8x4x EEPROM

Sergei Ianovich
2014-04-16T17:17:21Z

at24c128 write protection is implemented by a separate GPIO line.
EEPROM driver doesn't provide this option, so we implement it
in the board-specific device.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
---
v3..v4
* move DTS binding to a different patch (8/21)

v2..v3
* new patch

.../devicetree/bindings/misc/lp8x4x-bus.txt | 3 ++
Documentation/misc-devices/lp8x4x_bus.txt | 3 ++
drivers/misc/lp8x4x_bus.c | 50 ++++++++++++++++++++++
3 files changed, 56 insertions(+)

diff --git a/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt b/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
index 1b1776a..b0fb145 100644
--- a/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
+++ b/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
@@ -10,6 +10,8 @@ Required properties:
* the 8bit DIP switch
* the slot count register

+- eeprom-gpios : should point to active-low write enable GPIO
+
Example:

backplane {
@@ -17,4 +19,5 @@ Example:
reg = <0x0 0x2
0x9002 0x2
0x9046 0x2>;
+ eeprom-gpios = <&gpio 4 0>;
};
diff --git a/Documentation/misc-devices/lp8x4x_bus.txt b/Documentation/misc-devices/lp8x4x_bus.txt
index 829781b..78ea0a89 100644
--- a/Documentation/misc-devices/lp8x4x_bus.txt
+++ b/Documentation/misc-devices/lp8x4x_bus.txt
@@ -29,6 +29,9 @@ SYSFS
dip
RO - shows status of LP-8x4x 8bit DIP switch

+eeprom_write_enable
+ RW - controls write access to board's EEPROM (1 - enable)
+
rotary
RO - shows position of LP-8x4x rotary switch (0-9)

diff --git a/drivers/misc/lp8x4x_bus.c b/drivers/misc/lp8x4x_bus.c
index dfbc8c4..567fe078 100644
--- a/drivers/misc/lp8x4x_bus.c
+++ b/drivers/misc/lp8x4x_bus.c
@@ -9,6 +9,7 @@
* published by the Free Software Foundation or any later version.
*/
#include <linux/err.h>
+#include <linux/gpio/consumer.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/list.h>
@@ -27,6 +28,7 @@ struct lp8x4x_master {
void *count_addr;
void *rotary_addr;
void *dip_addr;
+ struct gpio_desc *eeprom_nWE;
struct device dev;
};

@@ -68,6 +70,40 @@ static ssize_t rotary_show(struct device *dev,

static DEVICE_ATTR_RO(rotary);

+static ssize_t eeprom_write_enable_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct lp8x4x_master *m = container_of(dev, struct lp8x4x_master, dev);
+
+ return sprintf(buf, "%u\n", !gpiod_get_value(m->eeprom_nWE));
+}
+
+static ssize_t eeprom_write_enable_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct lp8x4x_master *m = container_of(dev, struct lp8x4x_master, dev);
+ unsigned int val = 0;
+ int err;
+
+ if (!buf)
+ return count;
+
+ if (0 == count)
+ return count;
+
+ err = kstrtouint(buf, 10, &val);
+ if (err != 0) {
+ dev_err(dev, "Bad input %s\n", buf);
+ return count;
+ }
+
+ gpiod_set_value(m->eeprom_nWE, !val);
+
+ return count;
+}
+
+static DEVICE_ATTR_RW(eeprom_write_enable);
+
static ssize_t dip_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -81,6 +117,7 @@ static DEVICE_ATTR_RO(dip);
static struct attribute *master_dev_attrs[] = {
&dev_attr_slot_count.attr,
&dev_attr_rotary.attr,
+ &dev_attr_eeprom_write_enable.attr,
&dev_attr_dip.attr,
NULL,
};
@@ -156,6 +193,19 @@ static int __init lp8x4x_bus_probe(struct platform_device *pdev)
goto err_free;
}

+ m->eeprom_nWE = devm_gpiod_get(&pdev->dev, "eeprom");
+ if (IS_ERR(m->eeprom_nWE)) {
+ err = PTR_ERR(m->eeprom_nWE);
+ dev_err(&pdev->dev, "Failed to get eeprom GPIO\n");
+ goto err_free;
+ }
+
+ err = gpiod_direction_output(m->eeprom_nWE, 1);
+ if (err < 0) {
+ dev_err(&pdev->dev, "Failed to set eeprom GPIO output\n");
+ goto err_free;
+ }
+
m->slot_count = ioread8(m->count_addr);
switch (m->slot_count) {
case 1:
--
1.8.4.2