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    Subject[PATCH 04/31] staging: wfx: fix comment correctness
    Date
    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(-)

    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);

    --
    2.34.1
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