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Subject[PATCH v4] mtd: spi-mem: Add the default transfer length adjustments
    We need that to adjust the len of the 2nd transfer (called data in spi-mem)
if it's too long to fit in a SPI message or SPI transfer.

Fixes: c36ff266dc82 ("spi: Extend the core to ease integration of SPI memory controllers")
Cc: <>

Signed-off-by: Boris Brezillon <>
Signed-off-by: Chuanhua Han <>
Changes in v4:
-Rename variable name "opcode_addr_dummy_sum" to "len".
-The comparison of "spi_max_message_size(mem->spi)" and "len" was removed.
-Adjust their order when comparing the sizes of "spi_max_message_size(mem->spi)" and "len".
-Changing the "unsigned long" type in the code to "size_t".
Changes in v3:
-Rename variable name "val" to "opcode_addr_dummy_sum".
-Place the legitimacy of the transfer size(i.e., "spi_max_message_size(mem->spi)" and
-"opcode_addr_dummy_sum") into "if (! ctlr - > mem_ops | |! ctlr-> mem_ops->exec_op) {"
structure and add "spi_max_transfer_size(mem->spi) and opcode_addr_dummy_sum".
-Adjust the formatting alignment of the code.
-"(unsigned long)op->data.nbytes" was modified to "(unsigned long)(op->data.nbytes)".
Changes in v2:
-Place the adjusted transfer bytes code in spi_mem_adjust_op_size() and check
spi_max_message_size(mem->spi) value before subtracting opcode, addr and dummy bytes.
-Change the code from fsl-espi controller to generic code(The adjustment of spi transmission
length was originally modified in the "drivers/spi/spi-fsl-espi.c" file, and now the adjustment
of transfer length is made in the "drivers/spi/spi-mem.c" file).

drivers/spi/spi-mem.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 990770d..5374606 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -328,10 +328,23 @@ EXPORT_SYMBOL_GPL(spi_mem_exec_op);
int spi_mem_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
struct spi_controller *ctlr = mem->spi->controller;
+ size_t len = sizeof(op->cmd.opcode) +
+ op->addr.nbytes +
+ op->dummy.nbytes;

if (ctlr->mem_ops && ctlr->mem_ops->adjust_op_size)
return ctlr->mem_ops->adjust_op_size(mem, op);

+ if (!ctlr->mem_ops || !ctlr->mem_ops->exec_op) {
+ if (len > spi_max_transfer_size(mem->spi))
+ return -EINVAL;
+ op->data.nbytes = min3((size_t)(op->data.nbytes),
+ spi_max_transfer_size(mem->spi),
+ spi_max_message_size(mem->spi) -
+ len);
+ }
return 0;
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