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spi: core: add spi_split_transfers_maxwords

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Add spi_split_transfers_maxwords() function that splits
spi_transfers transparently into multiple transfers
that are below a given number of SPI words.

This function reuses most of its code from
spi_split_transfers_maxsize() and for transfers with
eight or less bits per word actually behaves the same.

Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
Link: https://lore.kernel.org/r/20230310092053.1006459-1-l.goehrs@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Leonard Göhrs 2023-03-10 10:20:52 +01:00 committed by Mark Brown
parent 93d205457d
commit 027781f392
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2 changed files with 53 additions and 0 deletions
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49
drivers/spi/spi.c
View File

@ -3622,6 +3622,55 @@ int spi_split_transfers_maxsize(struct spi_controller *ctlr,
}
EXPORT_SYMBOL_GPL(spi_split_transfers_maxsize);
/**
* spi_split_transfers_maxwords - split spi transfers into multiple transfers
* when an individual transfer exceeds a
* certain number of SPI words
* @ctlr: the @spi_controller for this transfer
* @msg: the @spi_message to transform
* @maxwords: the number of words to limit each transfer to
* @gfp: GFP allocation flags
*
* Return: status of transformation
*/
int spi_split_transfers_maxwords(struct spi_controller *ctlr,
struct spi_message *msg,
size_t maxwords,
gfp_t gfp)
{
struct spi_transfer *xfer;
/*
* Iterate over the transfer_list,
* but note that xfer is advanced to the last transfer inserted
* to avoid checking sizes again unnecessarily (also xfer does
* potentially belong to a different list by the time the
* replacement has happened).
*/
list_for_each_entry(xfer, &msg->transfers, transfer_list) {
size_t maxsize;
int ret;
if (xfer->bits_per_word <= 8)
maxsize = maxwords;
else if (xfer->bits_per_word <= 16)
maxsize = 2 * maxwords;
else
maxsize = 4 * maxwords;
if (xfer->len > maxsize) {
ret = __spi_split_transfer_maxsize(ctlr, msg, &xfer,
maxsize, gfp);
if (ret)
return ret;
}
}
return 0;
}
EXPORT_SYMBOL_GPL(spi_split_transfers_maxwords);
/*-------------------------------------------------------------------------*/
/* Core methods for SPI controller protocol drivers. Some of the

4
include/linux/spi/spi.h
View File

@ -1295,6 +1295,10 @@ extern int spi_split_transfers_maxsize(struct spi_controller *ctlr,
struct spi_message *msg,
size_t maxsize,
gfp_t gfp);
extern int spi_split_transfers_maxwords(struct spi_controller *ctlr,
struct spi_message *msg,
size_t maxwords,
gfp_t gfp);
/*---------------------------------------------------------------------------*/