[PATCH] spi: spi-mem: avoid mutating op template in spi_mem_supports_op()

[Santhosh Kumar K]

spi_mem_supports_op() accepts a const struct spi_mem_op pointer but
casts away const internally to call spi_mem_adjust_op_freq(). This
mutates the caller's op template, which causes stale max_freq values
when callers reuse persistent templates - subsequent calls won't
re-apply the device frequency cap since spi_mem_adjust_op_freq()
skips non-zero values.

Fix by operating on a stack-local copy instead.

Fixes: a4f8e70d75dd ("spi: spi-mem: add spi_mem_adjust_op_freq() in spi_mem_supports_op()")
Cc: Tianyu Xu <xtydtc@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Santhosh Kumar K <s-k6@xxxxxx>
---

This patch was tested on TI's
AM62Ax SK with OSPI NAND flash and
AM62Px SK with OSPI NOR flash.

log: https://gist.github.com/santhosh21/1747d197b12635bfaed741fca650a173

---
 drivers/spi/spi-mem.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index f64eda9bbd9f..a88b9f038356 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -279,13 +279,20 @@ static bool spi_mem_internal_supports_op(struct spi_mem *mem,
  */
 bool spi_mem_supports_op(struct spi_mem *mem, const struct spi_mem_op *op)
 {
-	/* Make sure the operation frequency is correct before going futher */
-	spi_mem_adjust_op_freq(mem, (struct spi_mem_op *)op);
+	struct spi_mem_op eval_op = *op;
+
+	/*
+	 * Work on a local copy; this is a pure capability check and must
+	 * not modify the caller's op. Stored templates with max_freq == 0
+	 * must remain unset so their frequency is always re-capped to the
+	 * current device maximum at execution time.
+	 */
+	spi_mem_adjust_op_freq(mem, &eval_op);
 
-	if (spi_mem_check_op(op))
+	if (spi_mem_check_op(&eval_op))
 		return false;
 
-	return spi_mem_internal_supports_op(mem, op);
+	return spi_mem_internal_supports_op(mem, &eval_op);
 }
 EXPORT_SYMBOL_GPL(spi_mem_supports_op);
 
-- 
2.34.1