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[04/31] staging: wfx: fix comment correctness

Message ID 20220113085524.1110708-5-Jerome.Pouiller@silabs.com
State New
Headers show
Series [01/31] staging: wfx: fix Makefile and Kconfig licenses | expand

Commit Message

Jérôme Pouiller Jan. 13, 2022, 8:54 a.m. UTC 
From: Jérôme Pouiller <jerome.pouiller@silabs.com>

Using DMA with stack allocated buffers is not supported, whatever the
value of CONFIG_VMAP_STACK.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
---
 drivers/staging/wfx/hwio.c | 12 ------------
 drivers/staging/wfx/hwio.h |  4 ++++
 2 files changed, 4 insertions(+), 12 deletions(-)
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Patch

diff --git a/drivers/staging/wfx/hwio.c b/drivers/staging/wfx/hwio.c
index 30eb888830d2..393bcb1e2f4e 100644
--- a/drivers/staging/wfx/hwio.c
+++ b/drivers/staging/wfx/hwio.c
@@ -14,18 +14,6 @@ 
 #include "bus.h"
 #include "traces.h"
 
-/*
- * Internal helpers.
- *
- * About CONFIG_VMAP_STACK:
- * When CONFIG_VMAP_STACK is enabled, it is not possible to run DMA on stack
- * allocated data. Functions below that work with registers (aka functions
- * ending with "32") automatically reallocate buffers with kmalloc. However,
- * functions that work with arbitrary length buffers let's caller to handle
- * memory location. In doubt, enable CONFIG_DEBUG_SG to detect badly located
- * buffer.
- */
-
 static int read32(struct wfx_dev *wdev, int reg, u32 *val)
 {
 	int ret;
diff --git a/drivers/staging/wfx/hwio.h b/drivers/staging/wfx/hwio.h
index ff09575dd1af..d34baae47017 100644
--- a/drivers/staging/wfx/hwio.h
+++ b/drivers/staging/wfx/hwio.h
@@ -12,6 +12,10 @@ 
 
 struct wfx_dev;
 
+/* Caution: in the functions below, 'buf' will used with a DMA. So, it must be
+ * kmalloc'd (do not use stack allocated buffers). In doubt, enable
+ * CONFIG_DEBUG_SG to detect badly located buffer.
+ */
 int wfx_data_read(struct wfx_dev *wdev, void *buf, size_t buf_len);
 int wfx_data_write(struct wfx_dev *wdev, const void *buf, size_t buf_len);