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spi: spidev: Enable control of inter-word delays 

Commit b7bb367afa 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: Jan Kundrát <jan.kundrat@cesnet.cz>
Signed-off-by: Mark Brown <broonie@kernel.org>
hifive-unleashed-5.2
Jan Kundrát 2019-03-07 15:29:42 +01:00 committed by Mark Brown
parent 4e3891a55f
commit 2ed6692e8c
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
2 changed files with 8 additions and 2 deletions
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4
drivers/spi/spidev.c
View File

@ -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);

6
include/uapi/linux/spi/spidev.h
View File

@ -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;