spi: Add check for 8-bit transfer with 8 IO mode support

The current SPI framework does not verify if the SPI device supports
8 IO mode when doing an 8-bit transfer. This patch adds a check to
ensure that if the transfer tx_nbits or rx_nbits is 8, the SPI mode must
support 8 IO. If not, an error is returned, preventing undefined behavior.

Fixes: d6a711a898672 ("spi: Fix OCTAL mode support")
Cc: [e-mail]
Signed-off-by: Cheng Ming Lin <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi.c

···
 				xfer->tx_nbits != SPI_NBITS_OCTAL)
 				return -EINVAL;
 			if ((xfer->tx_nbits == SPI_NBITS_DUAL) &&
-				!(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD)))
+				!(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD | SPI_TX_OCTAL)))
 				return -EINVAL;
 			if ((xfer->tx_nbits == SPI_NBITS_QUAD) &&
-				!(spi->mode & SPI_TX_QUAD))
+				!(spi->mode & (SPI_TX_QUAD | SPI_TX_OCTAL)))
+				return -EINVAL;
+			if ((xfer->tx_nbits == SPI_NBITS_OCTAL) &&
+				!(spi->mode & SPI_TX_OCTAL))
 				return -EINVAL;
 		}
 		/* Check transfer rx_nbits */
···
 				xfer->rx_nbits != SPI_NBITS_OCTAL)
 				return -EINVAL;
 			if ((xfer->rx_nbits == SPI_NBITS_DUAL) &&
-				!(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD)))
+				!(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD | SPI_RX_OCTAL)))
 				return -EINVAL;
 			if ((xfer->rx_nbits == SPI_NBITS_QUAD) &&
-				!(spi->mode & SPI_RX_QUAD))
+				!(spi->mode & (SPI_RX_QUAD | SPI_RX_OCTAL)))
+				return -EINVAL;
+			if ((xfer->rx_nbits == SPI_NBITS_OCTAL) &&
+				!(spi->mode & SPI_RX_OCTAL))
 				return -EINVAL;
 		}