thunderbolt: Call tb_eeprom_get_drom_offset() from tb_eeprom_read_n()

We are going to re-use tb_drom_read() for USB4 DROM reading as well.
USB4 has separate router operations for this which does not need the
drom_offset. Therefore we move call to tb_eeprom_get_drom_offset() into
tb_eeprom_read_n() where it is needed.

While there change return -ENOSYS to -ENODEV because the former is only
supposed to be used with system calls (invalid syscall nr).

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20191217123345.31850-3-mika.westerberg@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/thunderbolt/eeprom.c

@@ -130,13 +130,52 @@ static int tb_eeprom_in(struct tb_switch *sw, u8 *val)
 	return 0;
 }
 
+/**
+ * tb_eeprom_get_drom_offset - get drom offset within eeprom
+ */
+static int tb_eeprom_get_drom_offset(struct tb_switch *sw, u16 *offset)
+{
+	struct tb_cap_plug_events cap;
+	int res;
+
+	if (!sw->cap_plug_events) {
+		tb_sw_warn(sw, "no TB_CAP_PLUG_EVENTS, cannot read eeprom\n");
+		return -ENODEV;
+	}
+	res = tb_sw_read(sw, &cap, TB_CFG_SWITCH, sw->cap_plug_events,
+			     sizeof(cap) / 4);
+	if (res)
+		return res;
+
+	if (!cap.eeprom_ctl.present || cap.eeprom_ctl.not_present) {
+		tb_sw_warn(sw, "no NVM\n");
+		return -ENODEV;
+	}
+
+	if (cap.drom_offset > 0xffff) {
+		tb_sw_warn(sw, "drom offset is larger than 0xffff: %#x\n",
+				cap.drom_offset);
+		return -ENXIO;
+	}
+	*offset = cap.drom_offset;
+	return 0;
+}
+
 /**
  * tb_eeprom_read_n - read count bytes from offset into val
  */
 static int tb_eeprom_read_n(struct tb_switch *sw, u16 offset, u8 *val,
 		size_t count)
 {
+	u16 drom_offset;
 	int i, res;
+
+	res = tb_eeprom_get_drom_offset(sw, &drom_offset);
+	if (res)
+		return res;
+
+	offset += drom_offset;
+
 	res = tb_eeprom_active(sw, true);
 	if (res)
 		return res;
@@ -238,36 +277,6 @@ struct tb_drom_entry_port {
 } __packed;
 
 
-/**
- * tb_eeprom_get_drom_offset - get drom offset within eeprom
- */
-static int tb_eeprom_get_drom_offset(struct tb_switch *sw, u16 *offset)
-{
-	struct tb_cap_plug_events cap;
-	int res;
-	if (!sw->cap_plug_events) {
-		tb_sw_warn(sw, "no TB_CAP_PLUG_EVENTS, cannot read eeprom\n");
-		return -ENOSYS;
-	}
-	res = tb_sw_read(sw, &cap, TB_CFG_SWITCH, sw->cap_plug_events,
-			     sizeof(cap) / 4);
-	if (res)
-		return res;
-
-	if (!cap.eeprom_ctl.present || cap.eeprom_ctl.not_present) {
-		tb_sw_warn(sw, "no NVM\n");
-		return -ENOSYS;
-	}
-
-	if (cap.drom_offset > 0xffff) {
-		tb_sw_warn(sw, "drom offset is larger than 0xffff: %#x\n",
-				cap.drom_offset);
-		return -ENXIO;
-	}
-	*offset = cap.drom_offset;
-	return 0;
-}
-
 /**
  * tb_drom_read_uid_only - read uid directly from drom
  *
@@ -277,17 +286,11 @@ static int tb_eeprom_get_drom_offset(struct tb_switch *sw, u16 *offset)
 int tb_drom_read_uid_only(struct tb_switch *sw, u64 *uid)
 {
 	u8 data[9];
-	u16 drom_offset;
 	u8 crc;
-	int res = tb_eeprom_get_drom_offset(sw, &drom_offset);
-	if (res)
-		return res;
-
-	if (drom_offset == 0)
-		return -ENODEV;
+	int res;
 
 	/* read uid */
-	res = tb_eeprom_read_n(sw, drom_offset, data, 9);
+	res = tb_eeprom_read_n(sw, 0, data, 9);
 	if (res)
 		return res;
 
@@ -489,7 +492,6 @@ static int tb_drom_copy_nvm(struct tb_switch *sw, u16 *size)
  */
 int tb_drom_read(struct tb_switch *sw)
 {
-	u16 drom_offset;
 	u16 size;
 	u32 crc;
 	struct tb_drom_header *header;
@@ -517,11 +519,7 @@ int tb_drom_read(struct tb_switch *sw)
 		return 0;
 	}
 
-	res = tb_eeprom_get_drom_offset(sw, &drom_offset);
-	if (res)
-		return res;
-
-	res = tb_eeprom_read_n(sw, drom_offset + 14, (u8 *) &size, 2);
+	res = tb_eeprom_read_n(sw, 14, (u8 *) &size, 2);
 	if (res)
 		return res;
 	size &= 0x3ff;
@@ -535,7 +533,7 @@ int tb_drom_read(struct tb_switch *sw)
 	sw->drom = kzalloc(size, GFP_KERNEL);
 	if (!sw->drom)
 		return -ENOMEM;
-	res = tb_eeprom_read_n(sw, drom_offset, sw->drom, size);
+	res = tb_eeprom_read_n(sw, 0, sw->drom, size);
 	if (res)
 		goto err;