spi: Introduce SPI_INVALID_CS and is_valid_cs()

The SPI core inconsistently uses the marker value for unused chip select
pin. Define a constant (with appropriate type) and introduce is_valid_cs()
helper function to avoid spreading this inconsistency in the future.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240307150256.3789138-4-andriy.shevchenko@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 4ab155f698c88856e927f2b0c4a26c8c5c7bacf1..f18738ae95f8f9f76779921848470ee40783c130 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -608,6 +608,22 @@ static void spi_dev_set_name(struct spi_device *spi)
                     spi_get_chipselect(spi, 0));
 }
 
+/*
+ * Zero(0) is a valid physical CS value and can be located at any
+ * logical CS in the spi->chip_select[]. If all the physical CS
+ * are initialized to 0 then It would be difficult to differentiate
+ * between a valid physical CS 0 & an unused logical CS whose physical
+ * CS can be 0. As a solution to this issue initialize all the CS to -1.
+ * Now all the unused logical CS will have -1 physical CS value & can be
+ * ignored while performing physical CS validity checks.
+ */
+#define SPI_INVALID_CS         ((s8)-1)
+
+static inline bool is_valid_cs(s8 chip_select)
+{
+       return chip_select != SPI_INVALID_CS;
+}
+
 static inline int spi_dev_check_cs(struct device *dev,
                                   struct spi_device *spi, u8 idx,
                                   struct spi_device *new_spi, u8 new_idx)
@@ -618,7 +634,7 @@ static inline int spi_dev_check_cs(struct device *dev,
        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) {
+               if (is_valid_cs(cs) && is_valid_cs(cs_new) && cs == cs_new) {
                        dev_err(dev, "chipselect %u already in use\n", cs_new);
                        return -EBUSY;
                }
@@ -658,7 +674,7 @@ static int __spi_add_device(struct spi_device *spi)
        for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
                /* Chipselects are numbered 0..max; validate. */
                cs = spi_get_chipselect(spi, idx);
-               if (cs != 0xFF && cs >= ctlr->num_chipselect) {
+               if (is_valid_cs(cs) && cs >= ctlr->num_chipselect) {
                        dev_err(dev, "cs%d >= max %d\n", spi_get_chipselect(spi, idx),
                                ctlr->num_chipselect);
                        return -EINVAL;
@@ -698,7 +714,7 @@ static int __spi_add_device(struct spi_device *spi)
 
                for (idx = 0; idx < SPI_CS_CNT_MAX; idx++) {
                        cs = spi_get_chipselect(spi, idx);
-                       if (cs != 0xFF)
+                       if (is_valid_cs(cs))
                                spi_set_csgpiod(spi, idx, ctlr->cs_gpiods[cs]);
                }
        }
@@ -756,17 +772,8 @@ static void spi_set_all_cs_unused(struct spi_device *spi)
 {
        u8 idx;
 
-       /*
-        * Zero(0) is a valid physical CS value and can be located at any
-        * logical CS in the spi->chip_select[]. If all the physical CS
-        * are initialized to 0 then It would be difficult to differentiate
-        * between a valid physical CS 0 & an unused logical CS whose physical
-        * CS can be 0. As a solution to this issue initialize all the CS to 0xFF.
-        * Now all the unused logical CS will have 0xFF physical CS value & can be
-        * ignore while performing physical CS validity checks.
-        */
        for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
-               spi_set_chipselect(spi, idx, 0xFF);
+               spi_set_chipselect(spi, idx, SPI_INVALID_CS);
 }
 
 /**
@@ -1050,7 +1057,7 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
 
        spi->controller->last_cs_index_mask = spi->cs_index_mask;
        for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
-               spi->controller->last_cs[idx] = enable ? spi_get_chipselect(spi, 0) : -1;
+               spi->controller->last_cs[idx] = enable ? spi_get_chipselect(spi, 0) : SPI_INVALID_CS;
        spi->controller->last_cs_mode_high = spi->mode & SPI_CS_HIGH;
 
        if (spi->mode & SPI_CS_HIGH)
@@ -3333,9 +3340,9 @@ int spi_register_controller(struct spi_controller *ctlr)
                goto free_bus_id;
        }
 
-       /* Setting last_cs to -1 means no chip selected */
+       /* Setting last_cs to SPI_INVALID_CS means no chip selected */
        for (idx = 0; idx < SPI_CS_CNT_MAX; idx++)
-               ctlr->last_cs[idx] = -1;
+               ctlr->last_cs[idx] = SPI_INVALID_CS;
 
        status = device_add(&ctlr->dev);
        if (status < 0)