Unverified Commit 027781f3 authored by Leonard Göhrs's avatar Leonard Göhrs Committed by Mark Brown
Browse files

spi: core: add spi_split_transfers_maxwords 



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: default avatarLeonard Göhrs <l.goehrs@pengutronix.de>
Link: https://lore.kernel.org/r/20230310092053.1006459-1-l.goehrs@pengutronix.de


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 93d20545

drivers/spi/spi.c

+49 −0
Original line number Diff line number Diff line
@@ -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

include/linux/spi/spi.h

+4 −0
Original line number Diff line number Diff line
@@ -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);



/*---------------------------------------------------------------------------*/