[PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[Su Yanjun <suyanjun218@gmail.com>]

When i debug mcp2518fd, some method to track registers is
needed. This easy debug interface will be ok.

For example,
read a register at 0xe00:
echo 0xe00 > can_get_reg
cat can_get_reg

write a register at 0xe00:
echo 0xe00,0x60 > can_set_reg

Signed-off-by: Su Yanjun <suyanjun218@gmail.com>
---
 .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 132 ++++++++++++++++++
 1 file changed, 132 insertions(+)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index ab8aad0a7594..d65abe5505d5 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -27,6 +27,131 @@
 
 #define DEVICE_NAME "mcp251xfd"
 
+/* Add sysfs debug interface for easy to debug
+ *
+ * For example,
+ *
+ * - read a register
+ * echo 0xe00 > can_get_reg
+ * cat can_get_reg
+ *
+ * - write a register
+ * echo 0xe00,0x1 > can_set_reg
+ *
+ */
+static int reg_offset;
+
+static int __get_param(const char *buf, char *off, char *val)
+{
+	int len;
+
+	if (!buf || !off || !val)
+		return -EINVAL;
+
+	len = 0;
+	while (*buf != ',') {
+		*off++ = *buf++;
+		len++;
+
+		if (len >= 16)
+			return -EINVAL;
+	}
+
+	buf++;
+
+	*off = '\0';
+
+	len = 0;
+	while (*buf) {
+		*val++ = *buf++;
+		len++;
+
+		if (len >= 16)
+			return -EINVAL;
+	}
+
+	*val = '\0';
+
+	return 0;
+}
+
+static ssize_t can_get_reg_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int err;
+	u32 val;
+	struct mcp251xfd_priv *priv;
+
+	priv = dev_get_drvdata(dev);
+
+	err = regmap_read(priv->map_reg, reg_offset, &val);
+	if (err)
+		return 0;
+
+	return sprintf(buf, "reg = 0x%08x, val = 0x%08x\n", reg_offset, val);
+}
+
+static ssize_t can_get_reg_store(struct device *dev,
+				 struct device_attribute *attr, const char *buf, size_t len)
+{
+	u32 off;
+
+	reg_offset = 0;
+
+	if (kstrtouint(buf, 0, &off) || (off % 4))
+		return -EINVAL;
+
+	reg_offset = off;
+
+	return len;
+}
+
+static ssize_t can_set_reg_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return 0;
+}
+
+static ssize_t can_set_reg_store(struct device *dev,
+				 struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct mcp251xfd_priv *priv;
+	u32 off, val;
+	int err;
+
+	char s1[16];
+	char s2[16];
+
+	if (__get_param(buf, s1, s2))
+		return -EINVAL;
+
+	if (kstrtouint(s1, 0, &off) || (off % 4))
+		return -EINVAL;
+
+	if (kstrtouint(s2, 0, &val))
+		return -EINVAL;
+
+	err = regmap_write(priv->map_reg, off, val);
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+static DEVICE_ATTR_RW(can_get_reg);
+static DEVICE_ATTR_RW(can_set_reg);
+
+static struct attribute *can_attributes[] = {
+	&dev_attr_can_get_reg.attr,
+	&dev_attr_can_set_reg.attr,
+	NULL
+};
+
+static const struct attribute_group can_group = {
+	.attrs = can_attributes,
+	NULL
+};
+
 static const struct mcp251xfd_devtype_data mcp251xfd_devtype_data_mcp2517fd = {
 	.quirks = MCP251XFD_QUIRK_MAB_NO_WARN | MCP251XFD_QUIRK_CRC_REG |
 		MCP251XFD_QUIRK_CRC_RX | MCP251XFD_QUIRK_CRC_TX |
@@ -2944,6 +3069,12 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	if (err)
 		goto out_free_candev;
 
+	err = sysfs_create_group(&spi->dev.kobj, &can_group);
+	if (err) {
+		netdev_err(priv->ndev, "Create can group fail.\n");
+		goto out_free_candev;
+	}
+
 	err = can_rx_offload_add_manual(ndev, &priv->offload,
 					MCP251XFD_NAPI_WEIGHT);
 	if (err)
@@ -2972,6 +3103,7 @@ static int mcp251xfd_remove(struct spi_device *spi)
 	mcp251xfd_unregister(priv);
 	spi->max_speed_hz = priv->spi_max_speed_hz_orig;
 	free_candev(ndev);
+	sysfs_remove_group(&spi->dev.kobj, &can_group);
 
 	return 0;
 }
-- 
2.25.1