[PATCH] SPI: devices can require LSB-first encodings (ccf77cc4) · Commits · 戴 / test

drivers/spi/spi_bitbang.c

+10 −1

Original line number	Diff line number	Diff line
		@@ -187,13 +187,22 @@ int spi_bitbang_setup(struct spi_device *spi)
		if (!spi->max_speed_hz)
		return -EINVAL;

		bitbang = spi_master_get_devdata(spi->master);

		/* REVISIT: some systems will want to support devices using lsb-first
		* bit encodings on the wire. In pure software that would be trivial,
		* just bitbang_txrx_le_cphaX() routines shifting the other way, and
		* some hardware controllers also have this support.
		*/
		if ((spi->mode & SPI_LSB_FIRST) != 0)
		return -EINVAL;

		if (!cs) {
		cs = kzalloc(sizeof *cs, SLAB_KERNEL);
		if (!cs)
		return -ENOMEM;
		spi->controller_state = cs;
		}
		bitbang = spi_master_get_devdata(spi->master);

		if (!spi->bits_per_word)
		spi->bits_per_word = 8;

+5 −2

Original line number	Diff line number	Diff line
		@@ -35,10 +35,13 @@ extern struct bus_type spi_bus_type;
		* @chip-select: Chipselect, distinguishing chips handled by "master".
		* @mode: The spi mode defines how data is clocked out and in.
		* This may be changed by the device's driver.
		* The "active low" default for chipselect mode can be overridden,
		* as can the "MSB first" default for each word in a transfer.
		* @bits_per_word: Data transfers involve one or more words; word sizes
		* like eight or 12 bits are common. In-memory wordsizes are
		* powers of two bytes (e.g. 20 bit samples use 32 bits).
		* This may be changed by the device's driver.
		* This may be changed by the device's driver, or left at the
		* default (0) indicating protocol words are eight bit bytes.
		* The spi_transfer.bits_per_word can override this for each transfer.
		* @irq: Negative, or the number passed to request_irq() to receive
		* interrupts from this device.
		@@ -67,6 +70,7 @@ struct spi_device {
		#define SPI_MODE_2 (SPI_CPOL\|0)
		#define SPI_MODE_3 (SPI_CPOL\|SPI_CPHA)
		#define SPI_CS_HIGH 0x04 /* chipselect active high? */
		#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */
		u8 bits_per_word;
		int irq;
		void *controller_state;
		@@ -75,7 +79,6 @@ struct spi_device {

		// likely need more hooks for more protocol options affecting how
		// the controller talks to each chip, like:
		// - bit order (default is wordwise msb-first)
		// - memory packing (12 bit samples into low bits, others zeroed)
		// - priority
		// - drop chipselect after each word