Re: [PATCH] HID: intel-ish-hid: Fix -Wcast-function-type-strict in devm_ishtp_alloc_workqueue()

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

On Wed, 2025-10-22 at 00:49 +0200, Nathan Chancellor wrote:
> Clang warns (or errors with CONFIG_WERROR=y / W=e):
> 
>   drivers/hid/intel-ish-hid/ipc/ipc.c:935:36: error: cast from 'void
> (*)(struct workqueue_struct *)' to 'void (*)(void *)' converts to
> incompatible function type [-Werror,-Wcast-function-type-strict]
>     935 |         if (devm_add_action_or_reset(dev, (void (*)(void
> *))destroy_workqueue,
>         |                                          
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   include/linux/device/devres.h:168:34: note: expanded from macro
> 'devm_add_action_or_reset'
>     168 |         __devm_add_action_or_ireset(dev, action, data,
> #action)
>         |                                         ^~~~~~
> 
> This warning is pointing out a kernel control flow integrity (kCFI /
> CONFIG_CFI=y) violation will occur due to this function cast when the
> destroy_workqueue() is indirectly called via devm_action_release()
> because the prototype of destroy_workqueue() does not match the
> prototype of (*action)().
> 
> Use a local function with the correct prototype to wrap
> destroy_workqueue() to resolve the warning and CFI violation.
> 
> Closes: https://github.com/ClangBuiltLinux/linux/issues/2139
> Fixes: 0d30dae38fe0 ("HID: intel-ish-hid: Use dedicated unbound
> workqueues to prevent resume blocking")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

> ---
>  drivers/hid/intel-ish-hid/ipc/ipc.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hid/intel-ish-hid/ipc/ipc.c b/drivers/hid/intel-
> ish-hid/ipc/ipc.c
> index 59355e4a61f8..abf9c9a31c39 100644
> --- a/drivers/hid/intel-ish-hid/ipc/ipc.c
> +++ b/drivers/hid/intel-ish-hid/ipc/ipc.c
> @@ -924,6 +924,11 @@ static const struct ishtp_hw_ops ish_hw_ops = {
>  	.dma_no_cache_snooping = _dma_no_cache_snooping
>  };
>  
> +static void ishtp_free_workqueue(void *wq)
> +{
> +	destroy_workqueue(wq);
> +}
> +
>  static struct workqueue_struct *devm_ishtp_alloc_workqueue(struct
> device *dev)
>  {
>  	struct workqueue_struct *wq;
> @@ -932,8 +937,7 @@ static struct workqueue_struct
> *devm_ishtp_alloc_workqueue(struct device *dev)
>  	if (!wq)
>  		return NULL;
>  
> -	if (devm_add_action_or_reset(dev, (void (*)(void
> *))destroy_workqueue,
> -				     wq))
> +	if (devm_add_action_or_reset(dev, ishtp_free_workqueue, wq))
>  		return NULL;
>  
>  	return wq;
> 
> ---
> base-commit: 828aeac92901c1f31b51ae0b9d792b9af5bd3e27
> change-id: 20251021-ishtp-fix-function-cast-warn-660d3dae8af4
> 
> Best regards,
> --  
> Nathan Chancellor <nathan@kernel.org>
>