spi: Exctract spi_dev_check_cs() helper

It seems a few functions implement the similar for-loop to validate
chip select pins for uniqueness. Let's deduplicate that code in order
to have a single place of that for better maintenance.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240306160114.3471398-3-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -608,23 +608,35 @@ static void spi_dev_set_name(struct spi_device *spi)
 		     spi_get_chipselect(spi, 0));
 }
 
+static inline int spi_dev_check_cs(struct device *dev,
+				   struct spi_device *spi, u8 idx,
+				   struct spi_device *new_spi, u8 new_idx)
+{
+	u8 cs, cs_new;
+	u8 idx_new;
+
+	cs = spi_get_chipselect(spi, idx);
+	for (idx_new = new_idx; idx_new < SPI_CS_CNT_MAX; idx_new++) {
+		cs_new = spi_get_chipselect(new_spi, idx_new);
+		if (cs != 0xFF && cs_new != 0xFF && cs == cs_new) {
+			dev_err(dev, "chipselect %u already in use\n", cs_new);
+			return -EBUSY;
+		}
+	}
+	return 0;
+}
+
 static int spi_dev_check(struct device *dev, void *data)
 {
 	struct spi_device *spi = to_spi_device(dev);
 	struct spi_device *new_spi = data;
-	int idx, nw_idx;
-	u8 cs, cs_nw;
+	int status, idx;
 
 	if (spi->controller == new_spi->controller) {
 		for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
-			cs = spi_get_chipselect(spi, idx);
-			for (nw_idx = 0; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
-				cs_nw = spi_get_chipselect(new_spi, nw_idx);
-				if (cs != 0xFF && cs_nw != 0xFF && cs == cs_nw) {
-					dev_err(dev, "chipselect %d already in use\n", cs_nw);
-					return -EBUSY;
-				}
-			}
+			status = spi_dev_check_cs(dev, spi, idx, new_spi, 0);
+			if (status)
+				return status;
 		}
 	}
 	return 0;
@@ -640,8 +652,8 @@ static int __spi_add_device(struct spi_device *spi)
 {
 	struct spi_controller *ctlr = spi->controller;
 	struct device *dev = ctlr->dev.parent;
-	int status, idx, nw_idx;
-	u8 cs, nw_cs;
+	int status, idx;
+	u8 cs;
 
 	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
 		/* Chipselects are numbered 0..max; validate. */
@@ -658,14 +670,9 @@ static int __spi_add_device(struct spi_device *spi)
 	 * For example, spi->chip_select[0] != spi->chip_select[1] and so on.
 	 */
 	for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
-		cs = spi_get_chipselect(spi, idx);
-		for (nw_idx = idx + 1; nw_idx < SPI_CS_CNT_MAX; nw_idx++) {
-			nw_cs = spi_get_chipselect(spi, nw_idx);
-			if (cs != 0xFF && nw_cs != 0xFF && cs == nw_cs) {
-				dev_err(dev, "chipselect %d already in use\n", nw_cs);
-				return -EBUSY;
-			}
-		}
+		status = spi_dev_check_cs(dev, spi, idx, spi, idx + 1);
+		if (status)
+			return status;
 	}
 
 	/* Set the bus ID string */