[PATCH] spi: spi-mem: Adjust op len based on message/transfer size limitations

[Chuanhua Han]

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: <sta...@vger.kernel.org>
Signed-off-by: Chuanhua Han <chuanhua....@nxp.com>
Reviewed-by: Boris Brezillon <boris.brezil...@bootlin.com>
Signed-off-by: Mark Brown <broo...@kernel.org>
---
 drivers/spi/spi-mem.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 990770dfa5cf..ec0c24e873cd 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -328,10 +328,25 @@ 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;
+
+       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);
+               if (!op->data.nbytes)
+                       return -EINVAL;
+       }
+
        return 0;
 }
 EXPORT_SYMBOL_GPL(spi_mem_adjust_op_size);
-- 
2.17.1