staging: fbtft: fix 9-bit SPI support detection

Since the result of the setup function isn't adequate to check
9-bit SPI support, we better check bits_per_word_mask. Btw this
change avoids a NULL pointer dereference with master drivers
without a separate setup function.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 7 insertions, 14 deletions

diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c
index 23392eb6799e..7f5fa3d1cab0 100644
--- a/drivers/staging/fbtft/fbtft-core.c
+++ b/drivers/staging/fbtft/fbtft-core.c
@@ -1436,15 +1436,11 @@ int fbtft_probe_common(struct fbtft_display *display,
 
         /* 9-bit SPI setup */
         if (par->spi && display->buswidth == 9) {
-                par->spi->bits_per_word = 9;
-                ret = par->spi->master->setup(par->spi);
-                if (ret) {
+                if (par->spi->master->bits_per_word_mask & SPI_BPW_MASK(9)) {
+                        par->spi->bits_per_word = 9;
+                } else {
                         dev_warn(&par->spi->dev,
                                 "9-bit SPI not available, emulating using 8-bit.\n");
-                        par->spi->bits_per_word = 8;
-                        ret = par->spi->master->setup(par->spi);
-                        if (ret)
-                                goto out_release;
                         /* allocate buffer with room for dc bits */
                         par->extra = devm_kzalloc(par->info->device,
                                 par->txbuf.len + (par->txbuf.len / 8) + 8,
diff --git a/drivers/staging/fbtft/flexfb.c b/drivers/staging/fbtft/flexfb.c
index c763efc5de7d..3f380a0086c3 100644
--- a/drivers/staging/fbtft/flexfb.c
+++ b/drivers/staging/fbtft/flexfb.c
@@ -463,15 +463,12 @@ static int flexfb_probe_common(struct spi_device *sdev,
                         }
                         par->fbtftops.write_register = fbtft_write_reg8_bus9;
                         par->fbtftops.write_vmem = fbtft_write_vmem16_bus9;
-                        sdev->bits_per_word = 9;
-                        ret = sdev->master->setup(sdev);
-                        if (ret) {
+                        if (par->spi->master->bits_per_word_mask
+                            & SPI_BPW_MASK(9)) {
+                                par->spi->bits_per_word = 9;
+                        } else {
                                 dev_warn(dev,
                                         "9-bit SPI not available, emulating using 8-bit.\n");
-                                sdev->bits_per_word = 8;
-                                ret = sdev->master->setup(sdev);
-                                if (ret)
-                                        goto out_release;
                                 /* allocate buffer with room for dc bits */
                                 par->extra = devm_kzalloc(par->info->device,
                                                 par->txbuf.len + (par->txbuf.len / 8) + 8,