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Unverified Commit 2ed6692e authored by Jan Kundrát's avatar Jan Kundrát Committed by Mark Brown
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spi: spidev: Enable control of inter-word delays 



Commit b7bb367a added support for inserting delays in between
individual words within a single SPI transaction. This makes it
accessible from userspace.

WARNING: This delay is silently ignored unless the SPI controller
implements extra support for it. This is similar to how the in-kernel
users handle the other existing property, spi_transfer->word_delay.

Signed-off-by: default avatarJan Kundrát <jan.kundrat@cesnet.cz>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 4e3891a5

drivers/spi/spidev.c

+3 −1
Original line number Diff line number Diff line
@@ -276,17 +276,19 @@ static int spidev_message(struct spidev_data *spidev, 
		k_tmp->bits_per_word = u_tmp->bits_per_word;

		k_tmp->delay_usecs = u_tmp->delay_usecs;

		k_tmp->speed_hz = u_tmp->speed_hz;

		k_tmp->word_delay_usecs = u_tmp->word_delay_usecs;

		if (!k_tmp->speed_hz)

			k_tmp->speed_hz = spidev->speed_hz;

#ifdef VERBOSE

		dev_dbg(&spidev->spi->dev,

			"  xfer len %u %s%s%s%dbits %u usec %uHz\n",

			"  xfer len %u %s%s%s%dbits %u usec %u usec %uHz\n",

			u_tmp->len,

			u_tmp->rx_buf ? "rx " : "",

			u_tmp->tx_buf ? "tx " : "",

			u_tmp->cs_change ? "cs " : "",

			u_tmp->bits_per_word ? : spidev->spi->bits_per_word,

			u_tmp->delay_usecs,

			u_tmp->word_delay_usecs,

			u_tmp->speed_hz ? : spidev->spi->max_speed_hz);

#endif

		spi_message_add_tail(k_tmp, &msg);

include/uapi/linux/spi/spidev.h

+5 −1
Original line number Diff line number Diff line
@@ -66,6 +66,9 @@ 
 * @delay_usecs: If nonzero, how long to delay after the last bit transfer

 *	before optionally deselecting the device before the next transfer.

 * @cs_change: True to deselect device before starting the next transfer.

 * @word_delay_usecs: If nonzero, how long to wait between words within one

 *	transfer. This property needs explicit support in the SPI controller,

 *	otherwise it is silently ignored.

 *

 * This structure is mapped directly to the kernel spi_transfer structure;

 * the fields have the same meanings, except of course that the pointers
@@ -100,7 +103,8 @@ struct spi_ioc_transfer { 
	__u8		cs_change;

	__u8		tx_nbits;

	__u8		rx_nbits;

	__u16		pad;

	__u8		word_delay_usecs;

	__u8		pad;



	/* If the contents of 'struct spi_ioc_transfer' ever change

	 * incompatibly, then the ioctl number (currently 0) must change;